i

Images reproduced by courtesy of the Royal Library, Copenhagen.

2°K.B. 9,163

Images reproduced by courtesy of the Royal Library, Copenhagen.

2°K.B. 9,163

MATHEMATICAL

Colledions and Tranflations : In two

TOMES.

Images reproduced by courtesy of the Royal Library, Copenhagen.

2°K.B. 9,163

MATHEMATICAL

COLLECTIONS

AND

TRANSLATIONS.

The first

TOME

THE FIRST PART>

J. Galileus Galileus, His STSTEM E of the World.

II. Galileus, his ETISTLE to the gKAU^'J)

VUTC HE SSE Mother condllmim the Juthority of Sacred Sdil'PTUI^E iriThyloffl^md QoritrGverfies.

III. Johannes Kepler us, his 'J^e.conCilim of SC\[-

TTWR^E Texts, &c.

IV. DiDAcus a Stunica, his 'Reconcilin^s of SCRl-

^^rU'JiE Texts, &c.

sgari n u s,hts Epijlle to Father F^dKCTO^AC^llS, reconciling, the Juthorityof Sacred SC^ ITTUR E ^ and fHdgments of 'DiVines alledzed a^ainjt, &c.

By THOMAS SA LUST>Ul{r, Bfq.

LONDON,

Printed by W I L L i A M L e Y b our n e , mdclx i.

Images reproduced by courtesy of the Royal Library, Copenhagen.

2°K.B. 9,163

To the Noble and moft perfedly Accomplifhed

S'JOHN DENHAM

Knight of the Noble Order of the

BATH,

And Surveyor General of his Ma"" Works, &c.

Sir 3

Humbly begge your Pardon for bringing this Book under your Pro- tection. Were it a Work of my o wn>6r I any thing but the Tranfla- tour^I should mafter my Thoughts to a meaner Dedication,* But being a Colledion of fome of the greateft Matters in the V Vorld,and never made EngHsh till now , I conceived I might fooner procure their Welcome to a perfon fo eminent for Noble Candor , as well as for all thofe Intelledual Excellencies wherewith Your Rich Soul is known to be furnished. I refolvd to be as kind to this Book as I could,

and

and ferioufly confidering which way to efFect it , I at laft concluded to prefix Your Name, whom His Majefty and all his Subjedis^ (who have a higher Senfe and Judgement of Excel- lent Parts) know beft able to defend my Im- perfections. And yet I confefs there^s one thing makes againfh me? which is your eminent Integrity and great AlFe6bion to Truth, where- by my Lapfesin a Work ofthis Nature might j ullly defpair of Shelter , butithat the Excel- lency of Your Native Candor ftrives for Pre- dominancy over all Your great Abilities. For ^tis all-moll impoflible to think what Your Matchlefs V Vitisnot ableto Conquer,would Your known iViodefty but give leave: there- fore Gal/kus^Kep/er 4M'thok other Worthies in Learning are now brought before You in English Habit ; having changd their Latine, Italian and Frencji,whereby t:h^y werealmoft Strangers to our Natibn,unlefs tb fuch'is Yotij' who fo perfedly maftcr the Original^^¥know you have fo much and great imployrtieht fof His Majelly and his good 5ubje£tstfiafi shall; not robb you of another Minutes lofs ;^bdid^^' the liberty of fubfcribiiig my Self ; ^'fi-3nim3

, Moft Mumble ; Moft obedient Servant

THOMAS SALUSBURY.

READER,

}

f70t to

ZlhJ^^c. thai had bin fo lately emft led by the hand of ''^'''''''r^^^^^ time drawn

jZLZlon'hereofthe Sums that a Loyal Refle... ^r^^/^^^^^^^^

Tom me; and judo^d that the mo^ fafe, eafy^, and ^^f;J^^^^^^ ,,Lrd/the charge of th. P.-

deryrom of the Book^.to be contrtbHtary totheir ownComntment , byjut^jcrw ^

yilcation.

-'^rrEncourajreme.tfromthatpM^^^^^^

more than common Ajjifla

Trofefion in thBHfinefs. ^ Encouragement jrom y^^..^^^- - - y

rA/i ^J'-'^'^^^g ^^rlo^ ^ ProvoJTof .:^ec»i f^cu^^ ^-c^.A, Mai gave: Prof fj/'^^- - l^earned Dr ^Mathematicians and my %ealLFr,e»ds ^jr^j^r Miles Symner, (

^ /ffi'r/ffi^^ ^'^''^ "^^^ U^W./,.... ^.l^d me a concealment

of their ^ames.

^The names of thofe Anthorsani I ""'^'"' Trr^. J. ^ 7^^^,,^ Dlfil^Ei Tomes they are as conffiing of feveral pieces : Collettions I cm j „ot pretending to ar,j ihing more than

hereafter g.v. you ^'^'Sf in Italy (fj he c.L, hm Uve he.rd that though ,hp have

whr thefe Diahgues fouKl I" vanousenuna.nm ,J-^;.^ y,erc w th mufb detefiattoii perfected,

{Li .rJ S^grcdo the 7^^^^ « ban the_ V I jlM,^ his Ho-

mer Simplicius to perfoMte the {'"P''!'"'^^ .-^ ^ivl In iecU!>»,ng a.atnSt the Sam.an T>hUo.

,ourto i'concer.-d-^h^'''S!^«l'.-^ ~hU Argument, , and pur

fovhr, ""i "'^ hefupfoled) he.nr ,11 del w.thhy ''''""^f^^^f '^'^^^ D-JpleafureagahHcur ^u-

' L^hto the mouth ^fSimplicius; V^'«'^'«r" - ' "G^^

■with the Conpflori

thor,andthhl^.g.o other revenge fuffaent^^^^^^^

to condemn hm and p'ofcnk his B>.k'''Heret.cal;proptmng theU"J^ ^ ^ .^^ ^^^^ ^/-^^.^^^^^ _ ^Jf,^

Images reproduced by courtesy of the Royal Library, Copenhagen.

2°K.B. 9,163

Tft'ifcarrUge of the unfortuytate MathiasBemeggeius who firfi attempted to turn them wt» Lattne for the henefU vf the Le^irned H'orld. ^ I (hall not pre fume to Cenfttre the Qenfure which the Church of Rome pafi upon this DoElrlne and Its yljfertors Button the contrary, my Author having h'ln indefinite In his dlfcourfe , I fl, all forbear to exafperate, and attempt to reconcile [uch perfons to this Hypothefls as devout efieemfor Holy Scripture , and dutifull RefpeO: to Canonical InjunUtons hath made tofland off from this Opinion : and therefore for their fakes I have at the end of the Dla logues by way of fupplemetit added an Eplfile Galileo to Her Moil; Serene Hlghnefs Chriftina Lothalint^a the Grand Dutchefje Mother o/Tufcany ; as alfo certain Ahjlracls <f John Kepler , Mathematician to two Empe rours^ and Didaciisa Sinmc^ a famous Divine of Salamanca^wlth an Epijlle 0/ Paulo Antoiuo Fofcaiini a learn ed Carmelite of Naples, that'jhew the Authority of Sacred Scripture In determining of Phllofpphlcal and Natu ralControverfies '.hoping that the tngeniom & impartial Reader will meet with full fatisfaUlon In the fa e ay^nd leajl what I have fpoken of the prohibiting of thefe Pieces by the Inquljltlon may deterre any fcruiuTous perfonfrom reading of them , / have purpofely Inferted the Imprimatur by which that Office licenced them And. for a larger account of the Book, or Author, I refer you to the Relation of his Life, which Mbrln^ ut> the R.ar^ m the Secovd Tome. s f <^

concerning tende,

icmiv^f ^oiuni. ^ome may aueage, ana 1 doe confejs that 1 promijed to pubhfij the Life of Galileo this llace But the great mlfcamages of Letters from fome Friends In Italy and elfe where , to whom lama Debtor f rf veral Remarcfues^c^^ from whom J dally expeByet greater Helps concerning the Hlfiory of that famous P ConaJ'- thefe dlfappolntmentsjfavjoyned with the undeniable Re^uefi of fome Friends, who were Impatient to felcMU in Englifio , together with a confideration of the dlfproportlonate Bulkjhat would otherwlfe hive bin betwixt the two J>^o/umes,perf waded me to this exchange. This deviation from Promlfe I hope is Fenlal zr, ^ f v ./ ^ . v piatingofitlplead Supererrogatlon : having In each Tome made fo large Adltlons (thoud to Z,^^^^^^^ l^liltl ^^KT^' ^'.'i'.' PMjh.That thif'sfl^ffJppLr^^^

I them with the refi : a»d hope that ifyyu f^/«A- • '^>^ve done therein worth your acknajvledo-a

mem , you wjltyet at leafl account th^ ^ncreaje of my expence a fufficlent extenuation of the TrefpafjtlUa Additions have forced me tn mi^^it ptponyoar Patience In point of Time. ^ tnofe

zAsfor the fecond Tome, I have only this to affure the Generous Reader s\ i that I am very conftd t T fL n be much more punBual in publifhln^ that, than (for the reafons above related:) I was able to be lnhtlTn f U

thelVorld.

To fay nothing; of the dlf advantages of Tranflations in Zf»eraU this n^*yi',-^i> J. i.r r • - , roUald overffghts : but thofe of the T>rlnteJ dlf counted, nop he jiTfe ttf ""I^T n.an i.-..^\Atxhetr.this,l hive affumedthe Liberty I Jcthe Mifi"^^^^^^^^

rus In the Margent, not fo much to reproach him , as to convince thofe who told r»e tl,^, //^ ^^-''''^ beinegge- needlefs,having his Latine Tranfiatlon iy them.The like they f aid of the whole two ToZ IZ ""I'^'^f'^r^y P^'"^ me to qnenlon their Underfianding or Veraclty.F or fome of the Books were yet never evtan! A fV'''''^''^ the Mechanlcks of Monjieur Des Cartes , a Manufcrlpt which I found amongfi the many other RarY ' 'ch the welUhofen Library of my Learned and fTorthy Friend i>r.Charlcs Scarbui'^h- the Evn^riL '^^ ^^fJ""' ity.and the Life of r;;iIilro. both own : Others wen- l^rfarl^^ T^.l... ^JiA • ' . .f!^^^ "f ^^'«-

nis xjiaiogues ae Motu; {^never till now aone into anji j^anguage) which were jo mtermixt of Lai I ne and It r that the difficulty of the Stile, joyned with the Intricatnejfe of the SubjeB rendered them Unpleafant if-^ot lu't^ Vnintelllgible, tofuch as were not ^bfolute Mafters of both the Tongues. ^ ^"'^^^

To conclude- according to the entertainment that you p leaf e to afford thefe ColUaions,! fir all be encouratreJ t proceed with the Publication of a large Body of Hydrography-declaring the Hlfiory, Art, Lawes, andApendaZ of that I rincely Study of Navigation, wherein I have omitted nothing of note that can be found either i„ TUA ley, Fournier, Aurioarius, Nonius, Sncllus, Marfcnnus, Bayfius , Morifetus, Hlondus , Wagoner , abroad or leaTr amongn our Mariners at home, touching the Office of an Admiral, Commander, Pllot,CModellHl Shlvwrlcrhr gunner, ' i &"^y

But order requiring that F fi>ould dlfcharge my firfi Obligation before I contra^ a fecond: I (hall detelr you longer in the Portall,bHtput you intopojfejjfiottof the Premlfes^ '«7f«^#

JSlovemb. 20. 1661,

THE

ifertors. attempt

if 2>/W- nga the Empe-

t learn- I Natu^ • fame.

n. AnA

>e Rears

Moyfio, 'ttperiM- ' place : rforfe- •fonage: Caftelli nxt the the ex. •eat ex~ ppearby '.pltomes time of 'yafup- nts that

y °fpf*'

nvtedge- <it thofe

tifhall gforth 'felling eans a- ^es into

t's Er. ofHu. rneg^e- fjf pains caufed fiance ; hat en^

ed that ^echa- h' notes irve all tallan^ Jfbplly

SYSTEME

OF THE

WORLD:

IN FOUR

DIALOGUES

Wherein the Two

GRAND SYSTEMES

Oi 0 LO MY and COl" E ^(^^ ICU S

are largely difcourfed of ;

And the 1{EJS0 both "Phylofophical and Thy fa ah as well on the one fide as the other, impartially and indejinitely propounded ;

By qjLlLEUS QALILEUS LIU^CEUS. A (jemleman of ELO%E^Ce : Extraordinary Trofefor of

the Unthematicks in the N I V E R S I T Y ot T I S A and Chief Mathematicianto the GRAND DUKE of TV SCANT.

Uglified from the Original Italian Copy, hy THOMAS S ALU S B U RY.

A L C I N O li S J

S 1 N E C A ,

/«/«■ mllos magit qnm inter pHl LOSOPMOS effi debet a^ia tIBeRTAS.

LONDON, Printed by WILLIAM LEYBOUaNE. P^DCLXL

Images reproduced by courtesy of the Royal Library, Copenhagen.

2°K.B. 9,163

Images reproduced by courtesy of the Royal Library, Copenhagen.

2°K.B. 9,163

To the moft Serene Grand Duke

o F

T US C A N Y.

Hough the difference between Men and other living Greaturcs be very great, yet happly iie that fiiould fay that hecouIc| ftiew httle lets between jUari and Man would not Ipeafc marc than he llg^Uf^si^ might prove- What proportion doth one bear to athoufand > and yet it is a common Proverb , Ofie zPlfan is mrth Athoufand, yphen as a thqufand are not mrth one. This difference hatK dependence upon the different abiUties of their intelle- «auais i . ^vhich I reduce to the being , or not being a Philofo- pheri ih regard that Philofophy as being the proper food of liich asUveby itydiftinguifheth a Man from the common fence of the Vulgarin a more or lefs honourable degree accord- ing to the variety of that diet. In this fence he that hath the highefl looks, is of higheft quality ; and the turning over of the gr^^t Volume of Nature , which is *he proper Objedl of Philofophy is the way t6 make one look high; in which Book, although whatfoever we read , as being the Work of Al- mighty God , is therefore moil: proportionate yet notwith- flanding that is more abfolute and noble wherciif we more plainly deferne his art and skill. The ConHitution of the Vmvers, amoiig allPhyfical points that fall within Humane Compre- henfion,may;in my opinion, be preferred to the Precedency for if that in regard of univerfal extent it excell all others , it ouaht as the "Rule and Standard of the reft to gee before them in Nobility. Now if ever any pcrfons might challenge ie be fi^nally diflinsjuifhcd for Intelledfuals from other men/ ^ J ^ ■ • Tib ? ■

Ttokmey and (Jopernicus were they that have had the honour to fee fartheft into, and difcourfemoft profoundly of the fforlds Syflcme. About the Works of which famous Men theft Dia- lous being chiefly converfant , I conceived it n^y duty to De- dicate them only to Your Bighnefs. For laying all the weight upon thefe two , whom I hold to be the Ablefl: Wits that have left us their Works upon thefe Subjects 3 to avoid a Sole- cifmein Manners,! was obliged to addrels them to Him, who with me, is the Greateft of all Men , from whom they can re- ceive either Glory or Patrociny. And if thefetwoperfbns havefo farre illuminated my Underftanding as that this my Book may in a great part be confefled to belong to them , well may it alfbbe acknowledged to belong to Your HighnefsyXxnto whofe Bounteous Magnificence I pwe the time andleafiirel had to write it, as alfounto Your Powerful AfTiflance, (never weary of honouring me) the means that at length I have had to publifli it. May Your Htghmfs therefore be pleafed to accept of it according to Your accuflornedGoodnefs j and if any thingfhall be found therein, thatmaybefubfervient towards the information or fatisfadVion of thofe that are Lovers of Truths let them acknowledge it to bedue to Your Self who are fo expert in doing good, that Your Happy Dominion can not fhew the man that is concerned in any of thofe general Cala- mities thatdiflurb the Worlds fo that Praying for Your Profpe- rity , andcondnuancein this Your Pious and Laudable Cu- itome, 1 humbly kifs Your Hands h

Your (t5MoJl Serene Highne^es Moft Humble and moft devoted Servant and Subjed

.<3ALlLEO GALILEI.

'to

iDia- pDe-

Xreight ts that I Sole- ^who can re- erfons is my ■well ninto lure I jpever ■had

n-any wards ers of ■bare

Ml not Cala- rofpe- ; Cu-

THE AUTHOR' S

INTRODUCTION-

Judicious Reader ,

iHerel^aspubtiJhedfom years fince in Komt a falut if erous Edia , that , fir I the obviating of the dangerous Scandals of the pre/ent K^ge y tmfoftdafea^ I finable Silence upon the Pythagorean Opinion of the Mobility of the Earth, There Ti>ant not fUch as unadvtfedly affirm .that that Vecree^^as notthc produ- Bion of a fober Scrutiny of an illtnfirmed Pafsion',& one may hear fomemut- ter that Con fultors altogether ignorant of yifironomicalObfervations ought not clipp the vVingS of SpecuUttve Wits 'Wri^ ra/h Prohibitions. <JMy ^tale cmn- noTkee filef^^^^^* ^ ^^^^ t^eje t„uuf,jft^t>rHt» Jt ihvw^ht p't^ tct bcingthoroughly aC"

"quaintedlfiiththat prudent Determination, te appear openly upon the Theatre of thtWorld as a Wtt~ nefs of the naked Truth. I Ivas at that time m Rome-, and had not only the audiences , but applauds of themoft Eminent Prelates of that Court',norl»as that Decree PubLfhedTt^ithout Previous Nottcegiven me thereof Therefore it ts my refolution in theprefent cajt to give Foratgn T^ations to fee , that this point is as-^ellunderHoodtn Italy , and^arttcularly tnKom^ ,asTranfilptmDtligencecanimagine it to be ' and coUeOing together all the proper Speculations that concern the Copernican Sy ftcmc, to let them kno-^.that the notice of all preceded the Cenfure of the Roman Court 5 aMat there proceed from this Climate not only DoBrtnes fir the health of the Soul, but al/o tngentous Dtfcovenes for the recreating ef the CMind. r 1 1 r

To this end i have per fonmd the Copernican in this Difcourfe j proceeding upon an Hypothecs purely CHathematical-Jriving by allaitifictallfiayes to reprefint it Supertour, not to that of the Im- mobility of the Earth abfolutely, but according as it is mtnttonedby fome , that retetn no more, but the name (^/-Peripateticks . and are content, T^ithout going farther ,to adore ShadoT^s not phtlofophii.ing T^ith requifit caution, but mth the file remembrance of four Principles, but badly undoftood

We flo all treat of three princtpall heads. Ftrfi 1 loill endeavour tofheTV that all Experiments that can he made upon the Earth are infufficient means to conclude it's Mobility, but are indifferently applicable to the Earth moveable or immoveable : and J hope that on this occafion T^efhall difiover many obfir- vable Pajfa^es unknolt^n to the K^ncients. Secondly T»e "SPtll examine the CosLefttall Phc3enomcna that make for the Co^ctmcm \{y^o\hc^is,asifitl^eretoproveabfolutely vtBorious', adding by the T^ay certain neT^ obfervations , l^hichyet ferve only for the ^ftronomtcal Facility , not for Natural Necefity. In the third place I l^illpropofi an ingenuous Fancy. I remember thnt 1 have f aid many years fince. that theunknol^nProblemeofthe Tide mtght receive orne light admitting the Earths LMotion. This Pofitionofmine pafsing from one to another had mid charitable Fathers that adopted it for the Ijfue of their oT^n T»it.NoT^,becaufi no ftr anger mny ever appear that defending him- felhtth our armes.fhall charq^t us l^tth l^ant of caution in fi principal an ^cctdent,I have thought Jod to lay doipn thofe probabilities that 1»ould render it credible , admitting that the Earth did mo've I hope, that by thefe Con f derations the World >/// come to kno-^ , that if other T^ations have Naviaatedmorethan-^clpe have notfiudiedlefithanthey',& that ourreturnmg to afftrt the Earths Stability, and to take the contrary only fir a Mathematical Cz^nccio, proceeds not from tn^dvertency of T^hit others have thought thereof , but (had l^e mother inducements) from thofiReafons thatPtc^ ty,Reltgton,the Knoi^ledgcoftheDivintOmnipotency y andaconfitoufnefe of the incapacity of mans

VttderJlAnding diciate unto us, ^ ^

With

Images reproduced by courtesy of the Royal Library, Copenhagen.

2°K.B. 9,163

im.a I conceived it v(,y proper U exprefi theficcncemby T^,y ofvUlcgne, a.„ot bd',

/ometimisnelefscurKimthanthe principal x^rgument. ^ ' """"" 're

I chanced tohcf-veralycarsfirue, atfiverat ttma. m the S,upe„diom Citty of Venice T,hre I

c^methuher from Borence at ihefame time Signoxef MppoSaWhti itUr hln^l., ^ \.

.nj flcafire than on elevated SpecuUtLs. „ the ~ny of theTUA^^^^^^^

matters b, fore a certatn fer,pLick Phtlofopher y'hoJeLLIhavc n l'jJZi^^^^^^^

ing of the Truth, than theJan.e hehadacqitredhy ^r,ftot,ltcd iZKtlljl '""^"fi^nd-

No-\>, feeing that inexorable Heath hath deprived Venice and Florence o1 thofe it,o a,,., r:.L. ■ the very <^cr,d.an of thetr years, ld.drefLe, asfar ^my poor ab.l.ty-^luutl^^^^^^^ 'hetrl,vestothetrhonour>nthefeleavesJr,.gtngkrninL^M^^

Korjh. lithe HoneH Peripatetick T^ani his plate, to T^hom for his excefsive Jff'm! ,Z ^'"'['^"'fy- 'ner>tartesofi\mp\xtxxx%Jthoughtfit,T>ithomrnentioninghisoT»nNar>,eJu^^^ hefor^uchrelpeaed. Let thofe ,^,o great Souls .ever venerd,le to rny hem pU^^^^^ blick CMonument of my never-dytngLove ; andlet the rernernbrance of their pLZT'^r'^" delivering to Pojlertty the Confiderations that 1 have fromifed. ''io'[«ence afstfl mem

There cafrally happened (m Tt^as ufmtl) ftverat difcourfes at times betlteen th,n r- i l 1»h,cb had rather inflamed than faiisfied tn their T^us the thirfl they haZ l I ' ^""^'f"'"> '^^'■-■■---^'''S^''^^^ fir certain dayesU^i^^^^^^^

'^^/^o^icallytoeontempLetheWot^^^^^^^^

they look a dfcreet refoiution to meet together for certain dayes , u T^hiT'n ZrT^r '' '^t'"ff" theym^ghtbetakethemfelvesmoremethodiJlytoconUmpitethewZderfofr^^^^ t^e Earth: the place appotntedfortheirmetttngheingin the Palaceofthelob^^^^^^ due, but veryfhortcomplemms; Signore Salvifti began inthts m.J^er Sagtedo,-,//.r/*r

GALI-

ich:g

The CONTENTS of the FIRST

TOME

PART THE FIRST.

'Aghtsin rpetuaie ^rovnfy, he Com^ yfuthor this fu- ^ me in

%,the

mupon 'tafide, ^and in ^the

TrtMtife I. 11

III

IT,

lU.

IV.

! V.^ VI.

yn. yiii-

IX. X. XI.

XII.

GALlLEUS GAULEUS,hisSYS *EME of ttcWoRLD : inpour Dialogue His Epistle to her Serene Hichnesse CHRISTIANA LOTHERlNGA GRAND DuTCHEssE of TuSC ANY , toiiching the Ancient and Modern Doctrine of holy Fathers, aniJuDiciots Divine s, concerning the Authority of sacred Scripture in phylosophical Controversies.

JOHANNES KEPLER US, his Reconcilings of Texts of sacred Scripture tbatfccmtooppofctheDocTRiNE of the Earths mobili- ty : abftraftcdfrom his Introduction unco his learned Com men- tar ies upon the Planet MARS,

DIDACUS A STUNICA, a learned Spanish divine, hisRECoNCiLiNCs of the faid DOCTRINE with the Texts of sacred Scripture; abftra6ied from his Commentarie upon JOB.

PAULUS^ ANTONIUS FOSCARINUS , a Garme lite , his ^ p i s t l e to SEBASTIaNUS FANTONm, the General of his Order, concerning the Pythagorean and Gopernican Opinion of the mobility of THE Earth , and stabii.x±y of the Sun ; and of the nfw Systems or coNSTi'"'^'^^^ of the World: in wbfcii he rcconcileth the Texts OP s>..c^ED ScRi p TURE , and As sERTioN s ot Divine s , commonly alledged again ft 1 u w .

A Table of the most cbfervuble Perfons and Matters in ffe^FifftPart.

^ PART THE SECOND.

D.BENEDICTUS CASTELLUS, ABBot of S. Benedictus Aloysius, his Discourse of the mensuration of Running Waters : The Firft Book.

His Letter to GALlLEUS, rcptcfcnting the ftatp of the Lake of Perugia in Tuscany.

His Geometrical demonstrations of the measure of Runntt^g Waters.

His discourse of the men suratiOn of Running Waters : The Second

His Con s^id'e rations concerning the Lake of VENICE. In two dts courses.

His Rule for computing the quantity of mud and sand that Land-Floods bring down to, and leave in the La K E ot VENICE. ^ . .

His LETTERto Father FRANCESCO di S.GIVSEPPE, wherein , at the inftancc of PRINCE LEOP ALDO,he delivcreth his judgment concerning the turning FiUM E M oRT o (a River near Pi s a in TUSCANY ) into the Se a , and into the River Serch lo. .

His fccondLETTER inanfwcrtocertainOBjECTioNs propolcd,ana di f f icul- TiEs obferved by Signore BARTOLOTTI , in chat affair of the Divers ION of FiUME morto. n • /-

His Consideration upon the drain in g of th« p on tine hENN s ni CALA- BRIA ' V

His Consideration upon the draining of the Territories of BOLOG- NA, FERRARA, and ROMAGNA. .. ^

His Letter to D. FERRANTE CESABJN I, applying his Doctrine to the

MENSURATION of the LEN GT H,and Dl S TRIBUT I ON Of theOJlANTlTY

of the WATERS of Rivers, Springs, Aci:iEDUCT5,8ic. D CORSINUS, Superintendent of the general drain s, and Pre s iden t of ROMAGNA, his Relation of the ftarc of the Waters in the Territories of BOLOGNA and FERRARA. «^ Table cf the wofi thfervnyit Pcrfons Matters mentioned tn the Second Part.

* 2 The

Images reproduced by courtesy of the Royal Library, Copenhagen.

2°K.B. 9,163

The CONTENTS of the SECOND

TOME

Trtarife I.

IV.

pART THE FIRST.

r ALILBUS GAl-lLEUS, his mathematical discourses and demon*! sTRATioMS touching two NEW Sciences, pcrtainingtothc Me CH A* NICKS, and local motion: with an Appendix ot the Centre of

GRAVITY offomC SOLIDS in FoUl DI A L O CUE S .

Utc MECHANICKS; aNewPEicE. j u HPN ATUS De s CARTES, his Me c h an i c k s ; tranflatcd from his Fren cnl

manuscript; aNewPEicE. ARCHIMEDES, his TraftDE In sii>entibus Humido; With the Note s and

Demonstrasions of NICOLAUS TARTALhUS. in Two Books. G ALILEUS bis D 1 s c OUR s E of the things that move in or upon the W a t e r. i NICOLAUS TARTALEUS his Inventions for Diving under Wat '

Raising of Ships sunk,&c. in Two Books.

T E R)

II

III.

PART THE SECOND. i

EVANGELTSTA TORRlCELLTUS,hisDocTRiNE of Proie cTS,andTAB le«^ of the Ranges ot great Gunns of allforts; wherein he deters fundr^ Errors in Gunmery s An Epitome. T.S. his Experiments of the comparative Gravity of Bodiis in the

Aire and Water. , . _. „ CALILEUS G ALILEUS, his Life : mFivc Books, Book L Containing Five Chapters. ch4f. I. His Country.

3. His Par/»nci anj ExrraiO-inn. 3 His time ot Birth. : His fitft Education. ^\ His Maftcrs.

II. Containing T hree Chapters. />/»p. I- His j'ldgracnt in fcvcral Learnings.

2. Hi> Opinions and Doftrine.

3. His Auditors and Scholars.

III. Containing Four Chapters. Chap. 1. His behaviour in Civil Affairs.

2. His manner ot Living.

3. His morall Virtues.

4. His misfortunes and troubles. iV. Containing Four Chapters.

rhav I. HiipcrCondefcribcd.

^ ^' 2. His Will and Death.

3. His Inventions.

4i His Writings.

5. HisDiabgues of the Syfteme in parti.cLiIar,cohtarningA7i« Sia,o. I . O Aftronomy in General ; its Definition,Praifr6rS

3. Of the Doarine of the Earths Mobility.^J-c. ,-(5 Antimi.-tV

andPtogrcffe from P;,i.^,««othc\in,cof3

4. p theFollowcrsof<:»,,r.,w,u„tothctimeof£?ir«

5. O the fcvcrall Syftemcs amongft Afttonomer'.

6. Of the Allegations againfl the Syftcme in 77 Of A'^Ar"!- "''f T °* '^'th Anfwcrs totheffl^^

" OftheAlkgattonsfor thcC.,,r,.Syftemein ToArgumenK

9. The Conclufion Of the Whole Chapter. V. Containing Four Chapters.

I- His Patrons, Friends, and Emulators, a. Authors judgments of him. 5. Authors that have writ for, or againft him. 4. A Conclufion in certain Reflexions upon his whole Life,

A Table 0/ the wM Second Tome, j/j^

Images reproduced by courtesy of the Royal Library, Copenhagen.

2°K.B. 9,163

s and DEMON* CO the Me c H A*

IcCentre oi

this Frbn €9,1

the Notes and wo Books.

ic W A T E R.

NPER Water,

TS,andTAB le«

lODll s

in the

^PraiTe, Original. " iloguc of the

^ Its Antiguicy»

:imc of Copernicus'

timcofGtiii/gw. nomers.

'.Syftcmc, in 77 AnfwcrstotheitJ' in 50 Argument' gainftand for the

II Life.

G A L I L U

GalilsBus LyncsBUS,

SYSTEME

OF THE

The Firft Dialogue.

INTEKLOCVrOKS. jSALviAtus, Sagredus, aiid Simplicius.

SALVIATUS.

T was our ycfierdayes refolution, and a, grcemcnt,that we {hould to day d.fcourfe the moftdiftinaiy, and particularly wc could poffible, of the natural reatons,and their efficacy that have been hitherto al- ledged on the one Or other part , by the maintainers of the Pontions^ ^r«ff.f«/,.«, and PtolomanHch and by the tollowcrs CopernlcHs^w-;

■ of thfe eofcrmcan Syftcm : And bec^ufe

Copernicus placing the Earth among the moveable Bodie of tjea- vel comes to conftitute a Globe for the lame hke to a Plan« , .t would be good that we began our dilputation with the e^amuia- tionofwhat, andhow great the ^^^'p f'^^ ^^'^f'!".'^'^^^^ guments is, when they demonftrate, that th,s Hypotbefis n ,.npo -

z G. Galilee us. bis Syfieme.

Coeiefliai fubf^an- ^^^^^ ' Slncc that it IS neccffary to introduce in Nature,fubftanccs ces that arc fy>itite- different bctwixt theml'elvcs, that is^the Caleftial, and Elementa- ^f^wf/'X ^ ^^^^ impaflible and immortal , this alterable and corruptible. rablr.arifiecejfary Which argument Arijiutle handlctji in his book Cc^lo-i infinu- 'hx\Li\t'''°'' "-^atingit fiift, by fome difcourfes dependent on certain general af- fumptions^and afterwards confirming it with experiments and per- ticulardemonftrations : following the fame method, I will pro- pound 5 and freely fpeak my Judgement , fubmitting my felf to your ceniure, and particularly to Stmplic ins ^ 2i^to\xt Champion and contender for the Arifiatelian Do&rine. ^ Ariftotle maketh And the firft Step of the Fcripatetick arguments is that5whcre A- the mridferfeit, riftotU provcth the integrity and perfcftion of the World, telling

Brecaufe tt hath the , ^ . i i- ' r r r - » » i

threefold demenft- US , that It IS not a limpk luie, nor a bare lupcrhcies , but a body adorned with Longitude, Latitude, and Profundity , and becaufc there are no more dimenfioiis but thefe three , The World having them, hath ^^ill, and having all, is to be concluded perfe/&. And agaiivhatby fimple length, that magnitude is conftitilted, which is called a Line 5 to which adding breadth? there is framed the Su- perficies, and yet further adding the altitude or ptofounditys there refuUs the Body, and after thefe three dimenfions there is no pafling fafther,lo that in^-tbef^thr^ the iotcgfity, an4 to4i>.ipeak, tptaJiry is terminated; which I might but with juftic^ have requi- red Arijiotle to have proved to me by neceflary coniequcnces, the rather in regard he was able to do it very plainly, andfpccdily. Simp l. What fay you to the excellent demonflracions i-. the

Ariftotlcs^^w^"*- 3. 3-and4. Texts, after the definition of ContimtaP, have you it

^hedZ^fio^toL ^^^'^ P^""^^"^ ' ^^^^ ^^^'^ no more but three dimenfions,

^ three and no more, fot that thofc thrcc are all things, and that they are every where? 7hemmher three ^^^^ ^^ not this Confirmed by the Doftrine and Authority of the ceiUZTedLo-^gfi Fythagorians^ who fay that all things are determined by three, be- t^^Pythagorians ginning, middle, and end, which is the number of All ? And where leaye you that reafon, namely, thut at it were by the law of Na- ture, this number is ufed in the r4crilices of the Gods ? And why being fodiftated by nature, do \ve atiibute to thofc jihings th^^t are three, and nor to leUe, the title of all ? why of tWo jsit faid both,and not all, unlefs they be three ? And all thisDoflrrine yoii have in the lecond Text. Afterwardb in the third , Ad pleniorem Omnejotum Sc fcientiam^ we read that All^ the Whole , and Ferfecl^ are formally Pcrtc£tum. and the fame ^ and that therefore oaely the Body^ SLxnovigfh

magnitudes is perfcft : becaufe it is determined by three, which is All, and being divifible three manner of waies, it is every way di- vifible 5 but of the others, fome are dividible in one manner, and fome in two, becaufe according to the number affixed, they have ' their divifion and continuity, and thus one magnitude is continu- Or Solid. ate one way, another two, a third, namely the Body , every way.

More-

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2°K.B. 9,163

cs nta- ruptible. kinfitiu- Pralaf. and pcr- will pro- ly ielf to bampion

I, telling t a body [ becaufe Phaving I And d, which |the Su- there K is no iTpeak, ve requi-

I^s, the 1^: the you it Uions, f where? ty of the hree, be- id where Epf Na- n why B tba;t If f faid trine you morcm

Dialogue. L

Moreover in the fourth Text i doth he not after fome other Do- flirineS) prove it by another denionftration ? SciUcetyThsit no tran- fitionis made but according to fome defcS: (and fo there is a tran- fition or paffing from the line to the fupcrficies, becaufe the line is defeSive in breadth^ and that it is impoflible for the perfeft to want any thing, it being every way foi therefore there is no tran- fitionfrom the Solid or Body to any other magnitude. Now think you not that by all thefe places he hath fufficiently proved, how that there's no going beyond the three dimenfions , Length, Breadth , and Thicknefs , and that therefore the body or folid, which hath them all, is perfeft >

Salv. To tell you true, I think not my felf bound by all thefe rcafons to grant any more but onely this, That that which hath bcginning,middle,and cnd,may5and ought to be called perfeftiBut tliat then, becaufe beginning, middlcjand end,are Threc,the num- ber Three is a perfeft number , and hath a faculty of conferring FerfeSion on thofe things that have the fame, 1 find no inducement to grant h neither do I underftan4> nor belieye that, for example, of feet, the number th-^- t^ more perted then Tour ur rwo^ por do Iconceiyc nunibcr four to be ^ny imperfefiion to the Elc-» mcnts : and that they would be more perfefl: if they ^y^;e three. Better therefore it had been to have left thefe fubtlettes tp the ^etoricians^dind to have proved hisintent,by neccffary demonftra- tion j for fo it behoves to do in demonftrativc fcicnces.

S I M p L. You feem to fcorp thefe rcafons, and yet it is all the Doftrine of the Pythagorians^ who attribute fo much to numbers . and you that be a Mathematician^ and believe many opinions in the Py th^gprich^ Pl^lpfophy , feem now to contemn their My- fteries. J

Salv. That the Pythagorians had thcfcience ofpunibersin high eftecm, and that Plato himfelf admired humane underftand- i^Jg, and thought that it pertook of Divinity , for that it under- ftood the nature of numbers, I know very well, nor fliould I be far from being of the fame opinion ; But that the Myfteries foi? ^hich Pythagoras and his feft, had the Science of numbersin fuch veneration, are the follies that abound in the mouths and writings of the vulgar,! no waies credit:butrather becaufe I knovv that theyj to the end admirable things ijiight not be e^pQf<?d tp (he cout tempt, and fcorne of the vulgar, cenfured as facriiegiouSj f he pub? lifliing of the abftruce properties of Number^ , and i/icommen- furable and irrational quantities , by them inveftigated j and di- vulged,that he who difcovered them, was tormented in the other World : 1 believe that fome one of them to deter the common fort, and free himfelf from their inquifitivenefs, told them that the niyfteries ofnumbers were thofe trifles, which afterwards did fo

A 2 fpread

Plato held tfjit humane uader-^ fianding partook ofdivtnitjj^ecaHje it Understood num* hersi

The^yjlcry of Pythagorjck««iw- hers fabulous.

De Papyriop i- texcato , Gelliui i ->

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2°K.B. 9,163

4 G. G A L 1 L ^ u s, bis Sjllemel

fpread amongft the vulgar, and this with a difcretion and fubtlety refembling that of the prudent y6ung man, that to be freed from the importunity of his inquiiitive Mother or Wife, I know not whether, who preffcd him to impart the fecrets of the Senate, contrived that ftory , which afterwards brought her and many o« thcr women to be derided and laught at by the fame Senate.

S I M P L. I will not be of the number of thofe who arc over curi- ous about theP)/t/^^^(>ricl^ myfteries 5 but adhering to the point in hand j 1 reply, that the rcafons produced by Ariflotle to prove the dimenfions to be no more than three , feem to me conclu-^ dent, and 1 believe,That had there been any more evident demon- ftrations thereof, Arijtotle would not have omitted them.

S A G R. Put in at leaft,if he had known,or remembred any more. But you Sal^iatHs would do me a great pleafure to allcdge unto me fome arguments that may bcevident,and clear enough for mc to comprehend.

S A 1 V. I wilh and they (hall be fuch as are not oncly to be ap- prehended by you , but even by Simplicius himfclf : nor oncly to be comprehendca , but arc alfo already known , although hap- ly unobferved j and for the more eafie underftanding thereof, wc will take this Pen and Ink , which I fee already prepared for ACeomeHcMlde- fuch occafions, and defcribc a few figures. And firft we will note TfuJ^mnf^^^ [Fig.i • of this Dialog,'] thcfe two points AB, and draw

tr»p t mcnfton. ^^^^ ^j^^ ^^j^^^ ^j^^ curved lines,ACB,and ADB,and the

right line A B, I demand of you which of them, in your mind, is that which determines the diftance be tween the terms AB, & why?

5 A G R. 1 fliould fay the right line, and not the crooked, as well becaufe the right is fliorter , as becaufe it is one, fole , and deter- minate, whereas the others arc infinit,uneqnal,and longer^ and my determination is grounded upon that,That it is one,and certain.

S A LV. We have then the right line to determine the length be- tween the two termsi let us add another right line and parallel to AB,which let be CD,[f fo that there is put between them a fuperficies,of which I defire you to affign me the breadth,therefore departing from the point A, tell me how, and which way you will gOjto end in the line C D,and fo to point me out the breadth com- prehended between thofe lines j let me know whether you will terminate it according to the quantity of the curved line A E, or the right line A F, or any other.

S I M P L* According to the right A F , and not according to the crooked, that being already excluded from fuch an ufe.

S AG R. But I would take neither of them, feeing the right line A F runs obliquely ^ But would draw a line , perpendicular to C D, for this fliould feem to me the fliorteft, and the propereft of infinite that are greater^and unequal to one another,which may be

pro-

Di

ALOGUE

1.

)tlety ^- freed

i know Icnate,

iny Om

fr curi- point prove iconclu-^ ■eiiion-

Hmore.

Ige unto for mc

3e ap- ^onely

; thereof, >ared for will note Lnd draw ^,and the mind, is tSc why? ns well H deter- l^and my P^ain. ^th bc- irallel to :i them a i|trefore P^u will Kh corn- will or

^to the

Sht line lar to C pereft of I may be pro-

produced from the term A to any other part of the oppofite line CD.

Sa.lv. Your choice, and the reafon you bring for it in my judg- ment is moft excellent fo that by this time we have proved that the firft dimenfion is determined by a right line, the fecond name- ly the breadth with another line right alio , and not onely right, but withall, at right-angles to the other that dctermineth the length , and thus we have the two dimenfions of length and breadth, definite and certain. But were you to bound or termi- nate a height, as for example, how high this Roof is from the pave- ment, that we tread on, being that from any point in the Roof, we may draw infinite lines, both curved, and right, and all of di- yerfe lengths to infinite points of the pavement, which of all thefe lines would you make ufe of ?

S A G R. I would fallen a line to the Seeling,and with a plummet that fliouldhang at it, would let it freely diftend itfelftillit fliould reach well near to the pavenlent , and the length of fuch a thread being the ftreighteft and fliortefl of all the lines, that could pofsibly be drawn ^-^'•^ ^"^ ^^^^^ P^"^^ ^^^^ pavement, I would iay was the true height of this Room.

S A L V. Very well, And when from the point noted in the pave- ment by this pendent thread ( taking the pavement to be levcll and not declining) you fliould produce two other right lines j one for the length, and the other for the breadth of the fuperficies of thcfaid pavement , what angles fliould they make with the faid thread >

Sagr. They would doubtlefs meet at right angles, the faid lines falling perpendicular,and the pavement being very plain and levcll.

Salv. Therefore if you aflignany point, for the term from whence to begin your meafure , and from thence do draw a right line, as the terminator of the firft meafure , namely of the length, it will follow of neceffity, that that which is to defign out the largenefs or brcadth,toucheth the firft at right-angles,and that that which is to denote the altitude, which is the third dimenfion, goiog from the fame point formethalfo with the other two, not oblique but right angles, and thus by the three perpendiculars, as by three lines,one, certain, and asfhort as is poffible, you have the three dimenfions A B length-; A C breadth, and A D height i and becaufe, clear it that there cannot coneurre any more hneein thcfaid point, fo to make therewith ri^ht-angles , and the dimenfions ought to be determined by the fole right lines, which make between them- felves right-angles j therefore the dimenfions are no more, but three, and that which hath three hath all, and that which hath all, is divifible on all fides, and that which is fo, is perfefi:, &c, .

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2°K.B. 9,163

5 G. G A LiL^ us. his Syfteme.

Sim PL. And who faith that I cannot draw other lines ? why may not 1 protraft another line underneath, unto the point A, that may be perpendicular to the reft ?

Salv. You can doubtlefs, at. one and the fame point, make no more than three right lines concurre, that conftitutc right angles between themfelves.

Sagr. liccyvh^tSimpliciHSxacMs^ namely, thatfliould the faid D A be prolonged downward^then by that means there might be drawn two others, but they would be the fame with the firfi three, differing onely in this, th^it whereas now they onely touch, then they would intcrfwfi , but not produce new dimenfions. /« phjific4i proofs s I M P L. I will not fay that this your argument may not be con- cludent *, tut yet this I fay with ArijlotU^ that in things natural n- it is not alwaies necelTary, to bring Mathematical deinonft rations.

Sagr. Grant that it were fo where fuch proofs cannot be had yet if this cafe admit of them, why do not you ufe thein ? Bu^ it would be good we fpent no ifiore words on this particular, for I think that Sahiatus will yield , both to Ariflotle^ and you, with- out farther dcmQnftr^>^on>that the Wpild is a body, and perfeft, yea moft perfeftj as being the greateft work of Qod.

Salv. So really it is, chercfotre lcs^yi«g the geuerai coatempla- "Fartsol thiworU tion of thc wtolc, let US defccnd to the confidcration of its parts V^ZZTcZ which Ariftoth^ti his firft divifion,makes two, and they very diffe' fti4i Mnd Elemen- rent and ahiioft contrary to one anotfeec i namely the Cocleftial " Elementary : that ingencrable, incorniptible,^nalterabIe,un.' paffible, &c and this expofed to a continual alteration, mutati- on,&c. Which difterence, as from its original principle , he de- rives from the diverfity of local motions , andia ^hjs method he proceeds.

^Leaving the fcnfible, if I m^y (o fpeak, and retiring into the Ideal World, he begins Architeftonically to conlider^hat nature W motion of feeing thc principle of motion,, itfoUowcth that oat^ral.bodics be three kinds, right, indued with local motion. Next he dec 10^4] niotion tP i)« €ircHiar,&mixt. of three kinds, namely, circular, right, and mixt of «iglit and eif- CircuUr , and cuUr : and the two firft he calleth fimpte, for th^t ^ ^\\ hnes the ^""ifm ieZT7o- ^^^^^^^^ ^ and right arc onely fimple s and here fQmewhat rc- 7eedinlh /?m7/<r ft raining hi mfclf, hedcfinethanew, of fimple morions, one to be linei. circular, namely that which is made about the medium , and the

other namely the right, upwards, and downwards s.Oipvyards, „tUat wliich movcth from the downwards, that wjbjch goeth to-

wards the medium. . ^iid from hence heinfcrsjashe may byandne- f J ceffary confequence , that all fimple mot^)ns are <:(infined to thefe tbree kinds, namely,to the medium, from the medintu^ and about the medium 5 thc which correfponds faith he, with what hath been faid before of a body, that it alfo is perfefted by three things,aiid fo

IS

_ Dialogue. I. ^

is its motion. Having confirmed thefe motions,he proceeds faying; that of natural bodies fome being fimple , and fome compofed of them ( and he calleth fimple bodies thofe , that have a principle of motion from nature, as the Fire and Earth ) it follows that fimple motions belong to fimple bodies, and mixt to the com: pound; yet mfuch fort, that the compounded incline to the part predominant i n the compofition.

SAGR. Pray you hold a little Sal'z^iatm , for I find fo many doubts to fpring up on all fides in this difcourfe , that 1 {hall be conftrained , either to communicate them if I would attentively hearken to what you fliall add, or to take ofFmy attention froiri the things fpoken, if I would remember ob jeaions>

S A i. V. I will very willingly ftay , for that I alfo run the fame Hazard, and am ready at every flep to lofe my felf whilfi: I fail be- tween Rocks,and boifterous Waves, that make me, as they fay, to

V ' therefore before I make them more , propound

your difficulties. ^

Sagr. You and yfr/f -a-*'— ; w^ai firft takemea

uttleoutof theC?»«""e World, to tell me of the ^r<rWa«r# f ^T''"'*"' Wherewith it ought to be fabricated , and very appofitly begin to tell me, that a natural body is by nature moveable , nattire being ( 5is ellewhcre it is defined ) the principle of motion. But here I ~ am lomewhat doubtfull why ArijkotU faid not that of natural bo- dies, (ome are moveable by nature , and others immoveable, for that in the definition, nature is faid to be the principle of Motion, and Reft i for if natural bodies have all a principle of motion, cither he might have omitted the mention of Reft, in the definiti- oa ot nature :or not have introduced fuch a definition in this pl^.e. Mext, as to the declaration of what J rijiotle intends by fimple motions, and how by Spaces he determines them^calling thofe fim- ple, that arc made by fimple lines , which are onely the right, and circular, I entertain it willingly^ nor do I dcfire to tenter the ^-^'-^ "^^^^ inftance of the Helix,about the Cylinder which in that it is in e- tja^':^^:^ very part like to it felf, might feemingly be numb red amoiig fini^ puihc, pie lines. But herein I cannot concurre, that he fliouldfore^ • ftrain fimple motions (whilft he feems to go about to repeat the fame definition in other words) as to call one of them the ^notion about the;;;/c&w»/, the others 5'«r/>/;;/ ^ Deorfnnt, namely up- wards and downward i which terms are not to ^c ufed, out of the World fabricated, but imply it not onely made , but already in- habited by us ^ for if the right motion be fimple, by the fim|>iicity of the right line, and if the fimple motion be natural, it is made on every fide, to wit, upwards, downwards, backwards, forvvards, to' the right, to the left , and if any other way can be imagined, pro^ Videditbeftraight, it fliall agree to any fimple natural bc^dy^^ or

8

Ariftotle accom- moeUtes the rules ej

Archirc£):nre to the frtrnt tf the fVorld^ a'-dnotthe frame to thtrnltt.

Jtight met im, fame- times pmpl/'y ar.d fomtttmes mixt mc- C9rd$n^t9 Arift*

G. G A L 1 L /E u bis Syfieme.

if not fo, then the fuppofion of Arifiotle is defefiive. It appears moreover that yiri/?<7^/chinteth but one circular motion alone to be in the World, and confequently but one oncly Center, to which alone the motions of upwards and downwards, refer. All which arc apparent proofs, that -^ri/iot/^/ aim is, to make white black, and to accommodate ArohiteSiHr^ to the building, and not to modle the buildirig according to the precepts of Artbite^ure : for if I fliould fay that Nature in Univerfal may have a thou- fand Circular Motions , and by confequence a thoufand Cen- ters , there would be alfo a thoufand motions upwards , and downwards. Again he makes as hath been faid, a fimple motion and a mIxt motion, calling fimple , the circular and right \ and mixt, the compound of them two : of natural bodies he calls fome fimple ( namely thofe that have a natural principle to fimple mo- tion) and others compound : and fimple motions he attributes to fimple bodies, and the compounded to the compound but by compound motion he doth no longer underftand the mixt of right and circular, which may be in the World j but introduceth a mixt motion as impoiBblc, as it is impofliblc to mixe oppofite motions insiac in the fame right line, fo as to produce from them a motion partly upwards, partly downwards ^ and, to moderate fuch an ab- iurdity , and impoflTibility, he aflbrts that fuch mixt bodies move according to the fimple part predominant : which neccflitates others to fay, that even the motion made by the fame right line is fomecimes fimple, and fometimes alfo compound : fo that the fim- plicity of the motion , is no longer dependent onely on the fim- plicityof the line.

S I M P L. How? Is it not difference fufficient,that the fimple and abfolutc arc more fwift than that which proceeds from predomi- nion ? and how much fafl:er doth a piece of pure Earth defccnd than a piece of Wood ?

S A G R. Well, Simplicius j But put cafe the fimplicity for this caufe was changed, befides that there would be a hundred thou- fand mixt motions, you would not be able to determine the fim- ple j nay farther, if the greater or lefle velocity be able to alter the fimplicity of the motion, no fimple body (hould move with a fimple motion j fince that in all natural right motions, the veloci- ty is ever encreafing, and by confequence fl:ill changing the fimpli- city , which as it is fimplicity, ought of confequence to be immu- table, and that which more importeth, you charge Arifiotle with another thing , that in the definition of motions compounded, he hath not made mention of tardity nor velocity , which you now infert for a necefTary and eflfential point. Again you can draw no advantage from this rule , for that there will be amongft the mixt bodies fome, (and that not a few^ that will move fwiftly^

and

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2°K.B. 9,163

D I A L O G U E L " ^ and others more flowly than the fimple^ as for example, Lead, and Wood, in comparifon of earth j and therefore amongft thefe ffio- tions, which call you the llmple, and which the mixi.?

Sim PL. I would call that fimple motion , which is made by a fimplc body , and mixt, that of a compound body.

S A G R . Very well, and yet Simplicius 2l little before you faid, that the fimple, and compound motions , difcovered which were mixt, and which were fimple bodies ^ now you will have me by fimple and mixt bodies, come to know which is the fimplc , and which IS the compound motion : an excellent way to keep us igno- rant,both of motions and bodies. Moreover^ you have alfo a little above declared, how that a greater velocity' did not fuffice , but you feck a third condition for the definement of fimple motion, for which Arijiotle contented himfelf with one alone, namely, of the limphcity of the Space, ov Medinm : But now according to youi the fample motion, (hall be that which is made upon a fimplc line, with a ccrrain determinate velocity , by a body fimply moveable. JNow be It as you plcafe, and 1^. ro ^r^JiotU , who defi-

neth the mixt moti»^" °^ that compounded of the right and cit cular, but proauceth Hot any body, which naturally moveth with fuch a motion.

A/i^t^ J" ' •gain to , who having very well, and

Methodically begun his difcourfe ; but having a greater aim to k- L*^;. P^'cdcfigned in his minde, then that to

whish his method lead hiin, digreOing from the purpofe, he comes to aUert, as a thing known and manifcft , that as to the motions dircetly upwards or downwards, they naturally agree to Fire, and Harth and that therefore it is neceffajy, that befides thefe bodies, which are necr unto us, there muft be in nature another, to which the circular motion may agree : which (hall be fo much the more excellent by how much the circular motion is more perfea,then the ftreight, but how much more perfeft that is than this , he deter- mines from the greatnefs of the circular lines pcrfefiion above the , /• right line calling that perfeft, and this imperfeft j imperfeft, be- perfeH: , according caule it infinite it wanteth a termination, and end : and if it be fi- ^'f ""^'7 '"''^ -nite, there is yetfomething beyond which it may be prolonged. f^V^^^^^w^^ 1 nis is the bafis,ground work, and mafter-ftone of all the Fabrick oi^QArmotdian World, upon which they fup^rftrua all their Pther properties, of neither heavy nor light, of ingenerable incor- ^ptible, exemption from all motions , fome onely the local, Sec. ^^dall thefe pafiions he affirmetli to be proper to a fimple body that IS moved circularly j and the contrary qualities of gravitv, levity, corruptibility,8a:. heafli gns to bodies naturally moveable in a ftreight line , for that if we have already difcovered defeats in the foundation^ we may rationally queftion what foevcr may far-

B ' thcr

lO

G. Galil^us, Us Syfleme.

thcr built thereon. I deny not, that this which Ariftotle hitherto hath introduced, with a general difcourfe dependent upon univer- ial primary principles,hathbeen fince inproccfs of time, re-inforced with particular reafons, and experiments j all which it would be neceffary diftinftly toconfider and weigh , butbecaufe what hath been faid hitherto prefcnts to fuch as confider the fame many and no fmall diflSculties , ("and yet it would be neceffary, that the pri- mary principles and fundamentals, were Gcrtain,firm, and eftablilh- ed, that fo they might with more confidence be built upon J) it would not be amifs, before we farther multiply doubts, to fee if liaply (as I conjedure) betaking our fclves toother waies, we may not light upon a more direft and fecure methods and with better confidercd principles of Architefturc lay oui* primary fundamen- tals. Therefore fufpending for the prefent the method of Artjio- tlcy C which we will rc-affume again in its proper place, and parti- cularly examine « ) I fay, that in the things hitherto affirmed by '''ofed blithe aI' him, I agree with him, and admit that the World is a body enjoy- %ortoL \!rfemj ing all dimenfions, and therefore moft perfeS \ and I add, that as ordin<*t€. ^^^j^ 0eceffartly moft Ordinate, that is, having parts between

themfclves, with exquifite and moft perfeft order dil'pofcd j which affumption I think is not to be denied, neither by you or any

^^'s i*M P L- ^^^y ^ particular (of the worlds

diiTienfions) is taken from Ariftotle himfclfj and its denominati- on of ordinate fcems onely to be affumed from the order which it moft exaftly keeps.

Streight motion SaLV. This principle then cftabliflied, one may immediately *^!^ulxAVklj 'or- conclude, that if the entire parts of the World Ihould be by their difiMte. nature moveable , it is impoffible that their motions fliould be

right, or other than circular *, and the reafon is fufficiently eafie, and manifeft h for that whatfoever moveth with a right motion, changeth place ^ and continuing to move, doth by degrees more and more remove from the term from whence it departed, and from all the places thorow which it fucceffivcly paffcd ^ and if fueh motion naturally fuited with it, then it was not at the be- ginning in its proper place j and fo the parts of the World were not difpofed with perfeft order. But we fuppofe them to be per- feaiy ordinate, therefore as fuch, it is impoffible that they ftiould by nature change place, and confequently move In a right moti- jtiibt motion hy on. Again, the right motion being by nature infinite, for that nitture infinite, the tight line is infinite and indeterminate, it is impoffible that Motion hy a right any movcable cau have a natural principle of moving in a right popicT'*^^^ line^ namely toward the place whither it is impoffible to arrive, Natnre attempts thcrc being uo prac-finitc term '■, and nature, as Arjjiotle himfelf iVtlTeKffTilt' faith well, never attempts to do that which can never be done.

I

nor

Ibc .

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pri- liOi-

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may

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f

Joy-

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is ti- I'at

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iif

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Tive, mfdf

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D I A L b G li te I. ' n

nor effaies to move whither it is impoflible to arrive. And if any onefhoLild yctobjeft, that albeit the right line, and confcqucnt- ly the motion by it is producible in injiHitmn^ that is to fay, is in- terminate^ yet neverthclefs Nature, as one may fay, arbitrarily hath affigned them fome terms, and given natural inftinfts to its natural bodies to move unto the fame \ 1 will reply, that this might perhaps be fabled to have come to pafs in the firft Chaos, R^ghtn^ouonmigl^ where mdiftinft matters confufedly and mordmately wandered h firfi chaos. to regulate which. Nature very appofitely made ufeof right mo- f^^^^J^J'^'^^ tions, by which, like as the well-conftituted, moving, difdorder ^^^^^^^ /'^r^/^^^ themlelves, fowere they which were before depravedly difpoicd om of or- by this motion ranged in order :*but after their exquifite diftribu- tion and collocation, it is impolTible that there fliould remain na- tural incHnations in therri of longer moving in a light motion, from which now would cnfue their removal from their proper and natural place, that is to fay, their difordinaiion ^ we may there- fore fay that the right motion fervcs to conduft the matter to ereft the work j but once crefted, that it is to reft immoveable, or if moveable, to mov. — -"^'Y J'-^CuUrij. «„ur. we will (^yZT/^.u'lt with Flato, tncic mundane bodies, atter they had been made ^/««/>;^ /« artgh't and finiflied, were for a certain time moved by their Maker, in a ^'^'^^^^ ''''frcHUri' right motion, but that after their attainment to certain and dc- 7ccordhitov7i^^^^ terminate places, they were revolved one by one in Spheres, paf- fing from the right to the circular motion, whefeiu they have been ever fince kept and maintained. A fublime conceipt , and worthy indeed of Plato : upon which, I remember to ha;ve heard * Thus dorMis co^ our common friend the "^Lyncean A cade mic k^diicomk in this man- net, if I have not forgot it. Every body for any reafon conftitu- throughout this ted in a ftate of reft , but which is by nature moveable, being fet at liberty doth move ^ provided withal, that it have an inclina- i„g ,« a ftate of tion to fome particular place h for flibuld it ftand indifferently af- r e ft ^ (hail move

r r> 1 ,1 . t 1 ... n 1 • • f*»lefs it have an

icaed to all, it would remain m its reft, not having greater m- iMn^tton to fame ducement to move oneway than another. From the having o£ panicuUr pUcc. this inclination necelTarily proceeds, that it in its moving ftiall con- ^.^^^ ^,^,ahie ac- tinually incrcafe its acceleration, and beginning with a moft flow ceUrates its moti-^ motion, it fliall not acquire any degtee of velocity, before it 2) ,XI^r fliall have paffed thorow all the degrees of Icfs velocity, orgrea- ^v/j^,/, ter tardity : for pafling from the ftate of quiet (which is the in- ^'7. . . ■ hnite degree of tardity of motion) there is no reaion by which f,„^fromrejr, Y fliould enter into fuch a determinate degree of velocity, before cth '^^^^^^^fj^' |t fliall have entred into a lefs, and into yet a lefs, before it cntred into that : but rather it ftands with reafon, to pafs firft by thole degrees neareft to that from which it departed, and from thofe to the more remote ^ but the degree from whence the moveable Reft the i»ft»ite began to move, is that of extreme tardity, namely of teft. 'i''^<', t'^rdtty,

B 2 Nov^>

Images reproduced by courtesy of the Royal Library, Copenhagen.

2°K.B. 9,163

Nature^ to ixtro- dnce tn the move-

12 G. G A L 1 L ^ u bis SjjJeme.

The moveahle doth Now this acceleration of motion is never made, but when the 7»iy^^tZpp^^^^ moveable in moving acquireth it ^ nor is its acquift other than an eth nearer to its approaching to the place defired, to wit, whither its natural in- clination attrafts it, and thither it tendeth by the Ihorteft way \ namely, by a right line. We may upon good grounds therefore fay. That Nature, to confer upon a moveable tirft canftituted in reft a determinate velocity, ulcth to make it move according to a certain time and fpace with a right motion. This prefuppofed, able a certat» de- let US imagine God to have created the Orb %;,g, of Jupiter^ on gree of velocity, ^j^j^h he had determined to confer fuch a certain velocicv, which

made It move tn a j r • ii -r

ri^htiine, it ought aftctwards to retain perpetually uniiorm ? we may with Plato {^y^ that he gave it at the beginning a right and accelerate motion, and that it afterwards being arrived to that intended dc- Vmform velocity giee of Velocity, he converted its right, into a circular motion Z'^rZZ^L^ion!' the velocity of which came afterwards naturally to be uniform.

S AGR. 1 hearken to this Difcourfe with great delight 3 and I believe the content I take therein will be greater, when you have fatisfied me in a doubt : that is, Cwhich I do not very welicom- prehendj how it of neceffity enfucs, that a moveable departing al^'^Jp '^'A fj-oin j.^, and cutting into a motion to which it had a natural T-i^cfj^ty^^^^^^ inclination, it paffeth thorow all the precedent degrees of tardity, *i.^r«/ z/.- comprehended between any aflfigned degree of velocity^ and the locny interfofe. ^^^^ ^£ ^^^^ ^hich degtces ate infi nite ? fo that Nature was not able tp confer them upon the body of Jupitery his circular moti- on being inftantly created with fuch and fuch velocity. Nature doth mt SALv. I neither did, nor dare fay, that it was impoflible for '^rtttrJnZ God or Nature to confer that velocity which you fpeak of, imme^ degree of velocity^ diatcly j but this I fay, that dtfaBo fhe did not doit \ fo that the hov^heiti^e could. ^^.^^ ^^^^jj ^ ^^^|^ extra-natutal, and by confequence mi-

raculous.

5 A G R. Then you believe, that a ftone leaving its reft, and en- tring into its natural motion towards the centre of the Earth, paf- feth thorow all the degrees of tardity inferiour to any degree of velocity ?

Salv- I believe it, nay am certain of it \ and fo certain, that I am able to make you alfo very well fatisfied with the truth thereof.

Sagr- Though by all this daies difcourfe 1 Ihouldgainno more but fucK a knowledge, I fliould think my time very well beftowed.

Salv- By what I colk£t from our difcourfe, a great part of your fcruplelieth in that it fliould in a time, and that very (hort, pafs thorow thofe infinite degrees of tardity precedent to any ve- locity, acquired by the moveable in that time : and therefore be- fore wc go any farther, I will feek to remove this difficulty, which

fliall

Images reproduced by courtesy of the Royal Library, Copenhagen.

2°K.B. 9,163

Dialogue. I.

nan

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bich mh rate

ion.

me-

Lin,

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no |11

If

»rt, ^e- )e- ich all

in

ihall be an eafie task i for I reply, that the moveable paffi the a forefaid degrees, but the paffage is made without fl:aj_..^_. any of them j fo that the palTage requiring but one fole inftant of time, and every fmall time containing infinite inftants, we fliall not want enough of them to aflign its own to each of the infinite degrees of tardity, although the time were never fo ftiort.

S AGR. Hitherto I apprehend you y neverthelefsit is very much that that Ball (hot from a Cannon ( for fuch 1 conceive the ca- dent moveable ) which yet we fee to fall with fuch a precipice, that in lefs than ten pulfcs it will pafs two hundred yards of al- titude 5 fliouldin its motion be found conjoyned with fo fmall a degree of velocity, that, fhouldit have continued to have moved at that rate without farther acceleration, it would not have paft the fame in a day.

^S\LV- You may fay, nor yet in a year, nor in ten, no nor in a thoufand 5 as 1 will endeavour to (hew you, and alfo happily with- out your contradiaion, to fome fufliciently fimple queftions that I will propound to you. Theref«r^^ell me if you make any que- ftion of granting ti-*> ^^^^^ that ball in defcending gocth indca- fiaQitsi^r'f^ and velocity.

S A G R. I am moft certain it doth.

S AL V. And if 1 fliould fay that the impetus acquired in any place of its motion, is fo much, that it would fuffice to re-carry it to that place from which it came, would you grant it ?

S A G R. I fliould confent to it without contradiftion,provided al- waics, that it might imploy without impediment its whole impetus in that fole work of re-condufting it felf, or another equal toit, to that felf-famc height as it would do, in cafe the Earth were bored thorow the centre, and the Bullet fell a thoufand yards from the faid centre, for I verily believe it Would pafs beyond the centre^ afcending as much as it had defcended ^ and this I fee plainly in the experiment of a plummet hanging at a line, which removed from the perpendicular, which is its ftate of reft, and afterwards let go, falleth towards the faid perpendicular, and goes as far be- yond it 5 or onely fo much lefs, as the oppofition of the air, and line, or other accidents have hindred it. The like I fee in the wa- ter, which defcending thorow a pipe, re-mounts as much as it had defcended.

S A L V. You argue very well. And for that I know you will not fcruple to grant that the acquift of the impetus is by means of the receding from the term whence the moveable departed, and its ap« proach to the centre, whither its motion tendeth ^ will you flick to yeeld, that two equal moveables, though defcending by divers lines, without any impediment, acquire equal impetus^ provided that the approaches to the centre be equal ?

SAGR;

'3

The movfAhU de* farting from rejl pajfith thorow all degrees of velocuj. ■wtthopit l^ajtttgi*'' Any,

The pottderom fkc^^ ver defcending ac (ptireth jmpetu5 ftijficietit to rez carry it to tkb Hk.!^ height.

G, Galilm usy bis Syfieme.

S A G R- 1 do not very well underftand the qucftion. S A L V- 1 will exprelG it better by drawing a Figure : tlierefore IwiUfuppofetheline AB [in Fi^-B-] parallel to the Horizon, and upon the point B, I will ereft a perpendicular B C ; and after that I adde this flaunt line C A. Undcrftanding now the hne C • A to be an inclining plain exquifitely poliflied, and hard, upon which defcendcth a ball perfedly round and of very hard matter, and fuch another 1 fuppofe freely to dcfcendby the perpendicular C B : will you now confcfs that the impetus of that which dc- fcendsby the plain C A, being arrived to the point A, may be equal to the impetm acquired by the other in the point B, after thedcfcentbytheperpendicularCB? , r r <; » ^ B 1 lefolutely behevc fo : for in effeci they have both the ItTrS fame pro;imity to the centre, and by that, which 1 have already approachir^g to the their impetuofities wouM bc equally fufficicnt tore-carry

centre^ are eqt*al. gi'^Ait 5 ^ 1 •

them to the lame height.

S A L V- Tell me now what you believe the fame ball would do put upon the Horizontal plane A B ? L ■ Q /r^ p It would lie mil, the faid plane having no decimation.

taiipunthcmove' g al v- But on the inclmmg plane C A it would delcend, but M UethpiL . ^ ,han by the pcrpendicukr C B ?

.SaGR 1 may confidently anfwcr m the affirmative, it feem- . jj^e necefTary that the motion by the perpendicular C B (hmild be more fwift, thailby the inclining plane C Ai yet ne- verthelefs, if this be, how can the Cadent by the inclination ar- rived to the point A, have as much impetus^ that is, the fame de- gree of velocity, that the Cadent by the perpendicular {hall have in the point B ? thefe twoPropofitions feem contradiftory. rhtveiocitybjthe Salv- Then you would think it much morefalfc, fliould I incUningpUr^e^ e^ r ^j^^^ ^j^c velocity of the Cadents by the perpendicular, and VjXyZm^^^^^^^ are abfolutely equal-, and yet this is a Propotition

etiUu W ihemo- . ^ jg ^j^^ ^j^is that the Cadent moveth more fwittly by

uonyj theyerpe., ^ .j,^!,,^ ,han by the inclination. ^ ' ,

SAGR. Thefe Propotitions to my ears lound very harlh : and 1 believe to yours Simplicim ^

S I M p L I have the fame fenfe ot them. S ' I conceit you jeft with me, pretending not to compre- hend what you know better than my felf : therefore tell me S,m^ pliciHS , when you imagine a moveable more fwift than ano- thcr, what conceit do you fancy m your mmd ?

S I M P L. I fancie one to pafs in the fame time a greater ipace than the other, or to move equal fpaces but in lelTer time.

SALV. Very well: and for moveables equally fwitt, "^^^^^

your conceit of them ?

SiMPL- I fancie that they pafs equal fpaces in equal timcs^

Salv-

dicuUr fwift er than hy the inch nation.

D

lALOGUE. 1.

pace

Its

-V-

S A L V. And have you no other conceit thereof tf

Sim PL. This I think to be the proper definition < tions.

S A GR. We will add moreover this other : and call that equal velocity when the fpaces paffed have the fame proportion, as the ^r/'pS times wherein thev arpnaA o.,^;*.:. ^ ^-1 J /V • • ...nV.„«..;.HJ'

K • L — r**"*-*^ ij*v»^ i-Ait idiiic proportion, as tn(

times wherein they are paft, and it is a more univerfal definition. froporti^'n^tctf

S A L V. 1 1 is fo : for it comprehcndeth the equal fpaces paft irf '^"^ equal times, and alfo the unequal paft in times unequal, but pro- portionate to thofe fpaces. Take now the fame Figure,and apply- ing the conceipt that you had of the more haftie motion, tell me why you think the velocity of the Cadent by C B, is greater thanthevelocityof thcDcfccndent by CA> n n ^ r ^* ^ ^^^^^ ' becaufc in the fame time that the Cadent tharl " the Defcendent (hall pafsin C A, a part lefs

^ ^y^c i^u"^ ' thus it is proved, that the moveable moves more iwittly by the perpendicular, than by the inclination. Now ontider, it in this fame Figure on*- mav any way evince the o- ther conceipt, and "-^^^ the moveables were cauaily fwift by both the o A and C B.

S I M p L. I fee no fuch thing ^ nay rather it fcems to contradift what was faid before.

S A L V. And what fay you, Sagredm ? I would not teach you what you knew before, and that of which but luft now you pro^ ducedme the definition.

Sa gR- The definition I gave you, was, that moveables may be called equally fwift, when the fpaces paffed are proportional to the times in which they paffed i therefore to apply the defini- tion to the prcfent cafe, it will be requisite, that the time of dq- fcent by C A, to the time of falling by C B, Oiould have the fame proportion that the line C A hath to the line C B ^ but I underftand not how that can be, for that the motion by G B is fwifter than by C A.

Salv. Andyetyoumuftofneceffityknowit. Tell mc a little, do not thcfe motions go continually accelerating >

Sagr. They do i but more in the perpendicular than in the inclination.

Salv- But this acceleration in the perpendicular, is it yet not- withftanding fuch in comparifon of that of the inclined, tliat two equal parts being taken in any place of the faid perpendicu- lar and inclining lines, the motion in the parts of the perpendicu- lar is alwaics more fwift,than in the part of the inclination ?

Sagr. i fay not fo : but I could take a fpace in the inclinati- on, in which the velocity (hall be far greater than in the like fpacc taken in the perpendicular j and this (hall be, if the fpace in the

perpen^

G. Galilmus, bis Sjfleme.

perpendicular fliould be taken near to the end C, and in the in- clination, far from it.

SALV. You fee then, that the Propofition which faith, that the motion by the perpendicular is more fwift than by the incli nation, holds not true univerfally, but onely of the motions which begin from the extremity, namely from the point of reft : without which reftridiion, the Propofition would be fo deficient that its very direfi contrary might be true ; namely, that the mo- tion in the inclining plane is Iwifter than in the perpendicular • for It is certain, that in the faid inclination, we may take a fpace paft by the moveable in lefs time, than the like fpace paft in the perpendicular. Now becaufe the motion in the inclination is in fome places more, in fomc lefs, than in the perpendicular ; there fore infome places of the inclination, the time of motion of the moveable,lhaIl havc a greater proportion to the time of the motion ol the moveable, by lome places of the perpendicular, than the fpace paired, to the fpace paffed : and in Other places, the p^^o- portion of the time to the time, ftall be le'fs than that of the Ipace to the fpace.. As for example : two moveables dcpartinc. from their ^^icfcence, namely from the point C, one by the per- pendicular C B, [in and the other by the indlrnation C A m the time that, in the perpendicular , the moveable flia II K..,' paft all C B the other (hall have paft C T lefier. And thcrefo ^ the time by C T, to the imie by C B (which is equal ) lhall hav^ a greater proportion than the line C T to P R I, • \u l 4-othe/./., hath a greater propo';tion^h!„\oThl t^^^^ And on the contrary, if in C A, prolonged as much as if rel: fite, onefl^uldtake a part equal to C I, but paft in lZt r time; the time m the inclmation fiiallhave zhl proportion to the tiihe m the perpendicular, than the fpace to the fpace If therefore m tl^e mclination and pcrpendicwIaH= We tiiiy fuppofe iuchfpac^s and vcJocities, that the proportion bctVvten the faid fpaces be greater and lefs than the proportion of the times ; we may eafily grant, that there are alfo fpaces, by which the times ot the motions retain the fame proportion as the fpaces

S agb. I am already freed from my gr^ateft doubt, and con- ceive that to be not onely poflible, but necefl-ary , which I but jnow thought a contradiaion : but neverthelefs I underftand not

ye t that this whereof we now are fpeaking, is one of thefe' pofl.bieor neceffary cafes ; fo as that it Luld^e tru. tha the timeofdefcentby cA, to the time of the fall by C B hath the fame proportion that the line C A hath to C B [ wheLeit may without contradiaion be aflkmed, that the velocity by the i'cli^ nation G A, and by the perpendicular C B, are equal.^

SaLV: Content your fclf for this time, that I have removea

your

Dialogue. I.

yourbcfeiulicy; but for the knowledge of this, expeft it at fome othe.- cnxe, na.nely when you (hall fee the matters con e S SXS t""^^^^^^ ^^'''^'--k.; at which

fce how it t K P.^'"' '^'"g*^'- Whereby you

motions cilared ^ r f ' u 'f™ ^ ^'""'^^ ''^^'""'"g 'l'^ and the orh^f ^^^'^^"^^ <^ ^ g^^^^er than C T,

d^awrfroi A ""^"^heinterfeaionof the perpendicula

compare the ^oT" 'l^"''^^" by C A. But when we

thatn,adetprtrt^--^'^-?^ire^^^^^^^^^^ not, that themp.=-^ "y G A. continuing to defcend beyond mv arnvc to A in fuch a time as is in proportion to th. u ' as the line C A is to the line C Lretlf^g t^t.Tft purpofe , which was to (hew, that the grave moveable leaving pSnTt^r^f all^thede" Sy!

Slinfrhe V T"""' t-Sf ' ^^•^^'^y '''^^ « ^^q"-eth ber hTw^ Figure wliich we ufed before, letus remcm-

5^ and th7cfdT:' ?" ^'>^'>f-ndentby theinclin^n C «:quired eaud d P^P^^dicular C B, were found to have

proceed Tc, ^ A : now to

thrplte T """^ notfcruple to grant, that upon ano-

her plane left ftccp than AC ; as for example, A D [ia Fi^.< 1 the motion: of the defce«dent would be yet more flow thin in the

S he ,f; r * *! "^^'^ dubitable, but that there

may be^pknes fo httle elevated nbove the Horizon A B, that the

Teach .k ' 1'" ^^'"^ ' •'^ ^he longeft dme may

^ach the point A, which being to move by the plane A B,an infi-

flof J u.T"''^ ^"^""^ = ^"'^ f'le motion is made always more »^wiy,by hovv much the declination islefs. It muftbe therefore to" h r 4 V may be a point taken upon the term B, fo near the K II ! ^^^^ drawing from thence to the point A a plane, for not pafs it in a whole year. It is requifitc next

citv the K*ii T' tf^^f 'be namely the degree of velo-

Dninr A r ,^ ^° ^^^^ acquired when it arrivetb at the Fomt A,is luch,that (houldit continue to move with this felf-famc grec umtormly,that is to fay ,without accelerating or retarding;

c in

o G. G A L 1 L U S, bis Sjjieme.

mas much more time as it was hi coming by the inclining p^^^^^^ would pafs doable the Ipace of the plane inclined: namely (for example) if the ball had paft the plane D A in an hour, con- trnuingti move uniformly with that degree of veloc.ty wh.ch k i found to have in its arriving at the terin A, U Ihall pafs in an ■ hour a fpace double the length D A and becaufe C have faid\ the degrees of velocity acquired m the pomts B and A, by he Moveables that depart from any point taken in the perpend.cu- ar C B, and that defcend, the one by the inclined plane, the o- ther by the raid perpendicular, are always equal: therefore the cadent by the perpendicular may depart from a term fo near to B, that the degree of velocity acquired in B, would not lufticc (Itill maintaining the fame) to condua the moveable by a fpace dou- ble the length o£ the plane inchned in a year, nor m ten, no nor in a hundi-ed. We may therefore conclude, that if it be true, that according to the ordinary coutfe of nature a moveable, all external and accidental impediments removed, moves upon an in- elinine plane with greater and greater tardity, according as the inclination ftall be lefs : [o that in the end the tarduy comes to be • c • ^hich is, when the inclmation concludeth m, and joyneth To ?h?horizontalplane5 and if it be true Hkewifc, that thedc- oree of velocity acquired in fome point of the mclined plane, is o that degree of velocity which is found to be in the move- able that dcfcends by the perpendicular , in the point cut by a parallel to the Horizon, which palfeth by that point of the incli- ning pl^ne j it muft of neceflity be granted, that the cadent de- parting from reft, paffc-th thorow all the infinite degrees of tar- dity, and that confcqucntly, to acquire a determinate degree of velocity, it is neccfTiry that it move firft by right lines, defcend- ine by a fhort or long fpace, according as the velocity to be acqui- red ought to be either Icfs or gteater, and according as the plane on which it defcendeth is more or lels inclined ; fo that a plane may be given withfolmallincHnation, that to acquire in it the afliened degree of velocity,it muft firft move in a very great fpace, and take a very long timci whereupon in the horizontal plane,any how little foever velocity, would never be naturally acquired, fince that the moveable in this cafe will never move : but the

1 KniiTontal line, which is neither declined or incli- The circuUr mn- mouon by the hoiizontai iiuc, wm ^. r ■ .

u never is a tirGulat motioD about thc Centre : therefore the crcu-

T/r«t' lar motion is never acquired naturally, without the right motion ^l^r'C'^^'- precede it i but being once acquired, it will continue perpetually OrcUr mou^^ r I could .frith Other difcourfes evince and

}r ' demonftrate the fame truth, but I will not by fo great a digref- llon interrupt our principal argument : but rather wiU return to it upon fome other occafion j efpecially fjnce we now ^^""^^J^^^^

c

r

c

n

y

the :o B, (ftiU dou- )nor

Eu

phe

^neth lede- ic, is move- by a incli- kde. lar.

of end- icqui- plane

Pine the pace, e^any uired, ithe mdi-

lotion tually

Ggref- iirnto. edthe

Dialogue. I.

feme, not to ferve for a neceOary dcinonftration, but to adorn a riatontcli Conceit ; to which I will add another particular obfer- vanon of our Academic^., which hath in it fomcthing of admira^ ble. Let us fuppofe amongft the decrees of the dirine Hrchttea, a purpofe of creat.ng in the World thefe Globes, which we be- hold continually moving round, and of affigning the centre of their converfionsiand that in it he had placed the Sun immoveable, and had afterwards made all the faid Globes in the fame place, and with the intended inclinations of moving towards the Centre,

meH '^""^^ °f ^^l^'^i'y' ^J'i^h at firft fee-

we iS r r f^^I^ivineMinde ; the which being acquired, we laitly fuppofe that they were turned round, each in his Sphere retaining the faid acquired velocity : it is now demanded, in S o il^ ""^^ "^'^^""^^ Sun the place was where the

thS, ^"f P"^°"ily created ; and whether it be poffible that they ™ght all be created in the fame place ? To make this inve-

naln r J f ^'"""^ '""ft ^"^If"" Aftronomers the

magnitude of the Spheres in revolve, and like*

wife the time of .ut-^ revolutions : from which two eogn?t1onS gathered how much (f for example; J npiur is fwifter than S.- tHrne , and being found (as indeed it is) that jHfi^.r moves more fwiftly, It IS requifite, that departing from the fame altitude, 7«. O K more than ^^^«r«., as. we really know it is, its

Orbe being infenour to that of Satnrne. But by proceeding for- WL P^o^^i-''^ of the two velocities of J.p Jr and

what altitude and diftance from the centre of their revolutions,

nuagreea upon, it is to be fought, whether Wrs dctcevi^iaz^'i'cujlf thcn«. worn thence to his Orb, the magnitude of the Orb, and the ve- ""'^

tSn'^ T"??' ^P''^ "^''^ ^•'^ -^^''^ fo""d by calcula- t:^^

tion , and let tile like be done of the Earth, of Vcn^, and of"' Mercury ; the greatnefs of which Spheres, and the velocity of is ver^XiTablf^'^ fo nearly to what computation gives, that it

S A G R. 1 have hearkened to this conceit with extreme delight; and, but that I believe the making of thefe calculations truly would be a long and painfull task, and perhaps too hard for me lo comprehend, I would make a trial of them.

ALv The operation indeed is long and difficult ; nor could 1 oe certain to findc it fo readily ; therefore we fliall refer it to an- ner time, and for the prefent we will return to our firft propo- going on there where we made digrefllon j which, if I well member, was about the proving the motion by a right line of no

C a Hfei

Images reproduced by courtesy of the Royal Library, Copenhagen.

2°K.B. 9,163

20 G. G A L I L u s. Us Syftcme.

ufe, in the ordinate parts of the World j and we did proceed to Tay, that it was not fo in circular motions, of which that which is made by the moveable in it felf, ftill retains it in the fame place, Finite and termi- jf^j^j. vvhich catrieth the moveable by the circumference of a ZZ Zfo!der Z't circle about its fixed centre, neither puts it felf, nor thofe about it the parti of the difordci, for that fuch a motion primarily is finite and terniiinate (^though not yet finiflied and determined) but there is no point In the circular mo- the circumfcrencc, that is not the firft and laft term in the cir* 1h? llrclSfJ'lnce cuUtion *, and continuing it in the circumference affigned it, it is'theL7tZn^and Icavcch all the reft, within and without that, free for the ufc of others, without ever impeding or difordering them. This being a motion that makes the moveable continually l«^ye, and-con- Circular motion tinually arrivc at the end , it alone therefore can primarily be u- •w// is uniform, jjiform j for that acceleration of motion is made ia the moveable, when it goeth towards the term, to which it hath inclination i and the retardation happens by the repugnance that it hath to leave and part froni the lame term , and becaufe in circular mo- tion, the moveable continually leaves the natural term, and con- tinuaHy movotK towards the fame, therefore, in it, the repug- nance and inclination are always of equal force : from which e- quahty refults a velocity, neither retarded nor accelerated, i. e. an uniformity in motion. From this conformity, and from the being Circular motion terminate, may follow the perpetual continuation by fucceffively ma;Se continued ^citcT2itinQ^ the circulatious 5 which in an undeterminated line, perpetually. ^ motiou Continually retarded or accelerated, cannot ria-

%ightwo:ioncaK-mv2\\yh^, I fay, natutally^ becaufe the right motion which is Mt naturaiij he retarded, is the violent, which cannot be perpetual ^ and the ac- perpetuai. celcrate arrive th neceffarily at the term, if one there be ^ and if there be none, it cannot be moved to it, becaufe nature moves not whether it isimpolTible to attain. 1 conclude therefore, that the circular motion can onely naturally confift with natural bo- dies, parts of the univerfcjand conftituted in an excellent difpo- fure i and that the right, at the moft that can be faid for it, is Right motion af- ^/Tgj^p J ky naturc to its bodies, and their parts, at fuch time as

ftfrncd to natural "^J r i • l /I ^ J • J i

bodies , to reduce they lhall be out of their proper places, conltttuted m a depraved themto perfcB or- Jifr^ofi tinu, and for that caufc needinj^ to be redurcd by the fifiort-

der^when removed. '^^^J:'^^^'-**^^ ? , . . .

from their places, eft way to thcit natural ftate. Hence, me thmks, it may ratio- nally be concluded, that for maintenance of perfcft order amongft the parts of the World, it is neceifary to lay, that moveables are moveable onely circularly ^ and if there be any that move not 'K^f^W;,-^^ circularly, thefe of neceffityare immoveable : there being no- circuiar motion are thi^a but reft and circular motiou apt to the confcrvation of or- ajt^toconferveor^ ^^^^^ And I do not a Uttlc wondcr with my felf, thn Arifiotle, who held that the Terreftrial globe was placed in the centre of the World, and there remained immoveable, fliould not fay, that

of

to

th is lace, of a

nate )bint ^ cir* [t, it fcof »efHg con- ^ u- Me, fion V

:h e- e. an

Dialogue. I.

are moveable by naturcj and others immo- ore defined Nature, to be the prin .

of natural bodies fome are veable ; cfpecially having ciple of Motion and Reft.

SiMV L. Ariftotle, though of a very perfpicacious wit, would f^^rther than needed : holding in all his argumen- tatKHis, thatlenfiblc experiments were to be preferred before any realons founded upon ftrcngth of wit, and faid thofe which Ihouia deny the teftimony of fefife deferved t<) be punifticd with the lols ofthat fenfe , now who is iix blind, that fees not the parts of the Earth and Water to move, as being grave, natural- iy downwards, namely, towards the centre of the Univerfe af- ligned by nature her felf for the end and term of right motion deorfum; and doth not lik^wife fee the Fire and Air to move right upwards towards the Concave of the Lunar Orb, as to thd natural end of motion/Hr/«;« ? And this being fo mauifeftly feen, and we be,ng certain that e^em eBratto toLs d^partmm, why may we not alFert it for a true and manifrft propofiL, tha't the natural motion of the F.^.-*'- - "S°>- —ci^JT ' !

that of the Fire- nglit d modio i.',^~ y.. and SAI.V. The moft that you camprefcnd from this your Dif- courfc, were It granted to be true, is that, like as the parts of tL Earth removed from the whole, namely, from the place where they naturally reft, that is in (hort reduced to a depraved and dif. ordered difpofure, return to their place fpoataneoufly, and there- fore naturally in a right motion, (itbeing granted, that

ler eftrial Globe removed violently from -the place affigned It by nature, ,t would return by a right line. This, as I have laid, ,s the moft that can be granted you, and that onely for want ot examination ; but he that Hiall with exadnefs rcv.fe thefe things, Will hrft deny, that the parts of die Earth, in returnine to Its whole, move in a right line, and not by a circular or mixt ; and reauy you would have enough to do to demonftrate the contra- ry, as you (hall plamly fee in the anfwers to the particular reafons and experiments alledged by P^olomey zr^d AnftotU. Secondly, It another fliould fay that the parts of the Earth, go not in their motion towards the Centre of the World, but to unite with its *yh0lc,znA that for that reafon they naturally incline towards the centre of the Terreftrial Globe, by which inclination they con- P're to form and prelervc it, what other AU, or what other Centre

nK ^""^ ' "^^'^^ Terrene

Olobe, being thence removed, would feek to return, that fo the

zMA ^'^"^^ '"'S''^ ''■'^ ^° ^'"^ P"'*' ^ *t may be

aued. That neirher AriftotU, nor you can ever prove, that the arth de faSio is in the centre of the Univerfe; but if any Centre

may

31

Senjihle expert' mentsare to he pre* ferred before hw mane Argtimenta- tiofis.

He who denies fenfe^ deferVfs t§ i'e deprived of it, Senfe jhemeth thdt things grave move to f^tf medium, and the light te the concave.

It is (jueflionahU T^hetherdefcending^ rf eights move in 4 rf^ht line.

The Earth Iferi- cat yj con^i.^ ration of its parts to its Centre,

Images reproduced by courtesy of the Royal Library, Copenhagen.

2°K.B. 9,163

21 G. G A L I L ^ u s, hiiSyfteme.

rhSunm^repro'imy bc affigncd to the Univerfc, we ftiall rather find the Sun lf!hc%ZTrl placed in it^ as by the fequel you fliall undcrftand. th^JthcEanhV' Now, like as from the confentaneous confpiration of all the parts of the Earth to form its whole, doth follovVj that they with Nattitd iKcit»A' equal inclination concurr thither from all parts h and to unite tion of the parts of themfelvcs as much as is poflible together, they there fphciically fbe mrfto'go '[adapt themfelves i why may we not believe that the Sun, Moon, their centre. ^nd other mundane Bodies, be alfoof a round figure , not by o* ther than a concordant inftinfi, and natural concourfe of all the parts eompofing them ? Of which, if any, at any time, by any violence were feparated from the whole , is it not reafonable to think, that they would fpontaneoufly and by natural inftinS: re- turn ? and in this manner to infer, that the right motion agreeth with all mundane bodies alike. ; .

SrMPi.* Certainly, if you in this manner deny not onely the Principles of Sciences, but manifeft Experience, and the Senfes themfelves, you can never be convinced or removed from any o- pinion which you once conceit J therefore I will choofe rather to bc filent C^c^tj contra negantes principia non eft difputandnm) than contend with you. And infifting on the things alledged by you even now (fince you queftion fo nmch as whether grave move- ables have a right motion or no) how can you ever rationally dc- The ri^ht r>fotion ^y, that the parts of the Earth , or, if you will, that ponderous «»/ grave bodies ^^^^^-ers dcfccnd towatds the Centre, with a right motion j when- mantfefitofenfe. ^^^^^ ^ ^^^^ high Towcr, whofe walls are very upright and

perpendicular, you let them fall, they (hall dcfcend gliding and Aiding by the Tower to the Earth , exaflly in that very place where a plummet would fall,being hanged by ahnefaftned above, juft there, whence the faid weights were let fall > is not this a more than evident argument of the motions being right, and to- r^odrT^r.^"^ wards the Centre ? In the fecond place you call in doubt, whe- Watlrav'^e bodies thet thc parts of the Earth are moved, as Anftotle affirms, to- move with a» in- ^^^^^^ ^j^^ Centre of the World i as if he had not rationally de- TtZTeme7'tZ mo^^ whilfthethus argueth -, The

Vmverfe. motion of hcavic bodies is contrary to that of the light : but thc motion of the light is manifeft to be direftly upwards , namely, towards the circumference of thc World, therefore the motion of the heavie is dire&ly towards the Centre of the World : and it j{eavie bodies happens per accidens^ that it be towards the centre of the Earth, TeZlJoTthlEal^h ^^^^ ^his ftriveth to be united to that. The fecking in the l[7zcadJs. ' next place, what a part of the Globe of the Sun or Moon would do, were it feparated from its whole, is vanity *, becaufe that there- To feek w^^^ by that is fought, which would be the confequence of an impoffi- tPOHid follow p*pon i^.j.^^ . .^^ regard that, as Ariftotle alio dcmonftrates, the coeleftial folly. bodies are impaflible, impenetrable, and infrangible • fo that fuch

a cafe

i

»on, ^ o-

}US

us a I to-

lere- ftial

Dialogue L' a cafe can never happen: and though it fliould, and that the fe-

2?

parated part Ihould return to its whole, it would not return as neither hiavte mr grave or light, for that the fame Arijiotle provcth, that the C(£- ^^^f^J^-j^^^^^^^ Icftial Bodies are neither heavie nor light. ^

S A L V. With what reafon I doubt, whether grave bodies move by a right and perpendicular line, you ftall hear, as I faid be- fore, when I lhall examine this particular argument. Touching the fecond point, I wonder that you fliould need to difcover the Paralogifm of Ariftotle^ being of it fclf fo manifefi ^ and that you perceive not, that AnftotU fuppofeth that which is in quefti- on : therefore take notice.

Sim PL. Pray Sahiatns fpeak with more refpefi of Arijioth: for who can you ever perfwade, that he who was the firjft, only, and admirable explainer of th^SyUogiflick forms of demonfrration, Arii^ode cannot oiElenchs.oi the manner of difcovering5(7pfc//ii;/j',r4r^%//«j',aLd IhJ'Z^''' ^J^^ m (hortjof all the parts of L(?^i4,fliould afterwards fo notorioufly 'a^C*'"' equivocate in impofing that for known, which is in queftion ? It would be better, my Mafters, firft perfedly to underftand him, and then to try, if you have ^ 'T '^'^V him.

Salv. Simpli-^;^^ ^^/^e here familiarly difcourfing among our fcives, to inveftigate fome truths I (hall not be difpleafed that you difcover my errors , and if I do not follow the mind of Arijiotle, freely reprehend me, and 1 fliall take it in good part. Onely give me leave to expound my doubts, and to reply fome- thing to your laft words, telling you, thsit Logic l^, as^it is well underftood, is the Organe with which we philofophate , but as it may be poffible, that an Artift may be excellent in making Or- gans, but unlearned in playing on them, thus he might be a great Logician, butunexpertinmakingufeof L<?^i/:^S like as we have many that theorically underftand the whole Art of Poetry , and yet are unfortunate in compofing but meer four Verfes j others 'A famous /M/r/« en;oy all the precepts of t^ifjci* , and yet know not how to paint fainter, a Stoole. The playing on the Organs is not taught by them who know how to make Organs, but by him that knows how to play on them : Poetry is learnt by continual reading of Poets : Limn- ing is learnt by continual painting and deligning : Demonftration from the reading of Books full of demonftrations, which are the Mathematical pnely, and not the Logical. Now returning to our purpofe, I fay, that that which Arijiotle feeth of the motion of %ht bodies, is the departing of the Fire fro^^ ^ny pajt of the Siiperficies of the Terreftrial Globe, and dir^ftly retreating from It 5 niounting upwards ^ and this indeed is to move towards a Circumference greater than that of the Earth j yea, the fame A- rijlotU mzliQs it to move to the concave of the Moon, but that this circumference is that of the World, or concentrick to it, fo

that

Images reproduced by courtesy of the Royal Library, Copenhagen.

2°K.B. 9,163

24

Tavalogifmof A- riftotle, $tj proving the Earth to he in the Centre of the

mrid.

The VdrMlbgifme c/ArUiodc another vto) dtfcovered.

G. G A L I L ^ u his Syjleme,

that to move towards this, is a moving towards that of the World, that he cannot affirm, unlcfs he fuppofcth, That the Centre of the Earth, from which we fee thefe light alcendent bodies to depart^ be the fame with the Centre of the World ^ which is as much as to fay, that the terrefirial Globe is coiiftituted in the midft of the World : which is yet that of which we were in doubt, and which AriBotle intended to prove. Atid do you fay that this h not a manifeft faralogifm ?

Sagr. This Argument of ^ri/?of/e appeared to me deficient alfo, and w<?«-concludent for another refpeft though it were granted, that that Circumference, to which the Fire dircfily mo- veth, be that which includeth the World : for that in a circle, not onely the centrcjbut any other point being taken^every move- able which departing thence, fhall move in a right Hne, and to- wards any whatfoever part, fliall without any doubt go towards the circumference, and continuing the motion, fhall alfo arrive thither h fo that wc may truly fay, that it moveth towards the circumference : bur yet it doth not follow, that that which mo- veth by the fame line with a contrary motion, would go towards the centre, u^lc^^ when the point taken were the centre it fclf, or that the motion were made by that onely line, which produced from the point affigned, paffcth thorow the centre. So that to fay, that Fire moving in a right line, goeth towards the circumfe^ rencc of the World, therefore the parts of the Earth which by the fame lines move with a^ contrary motion, go towards the cen- tre of the World, concludeth ret , unlefs then when it is pre- fuppoied, that the lines of the Fire prolonged pafs by the centre of the World ^ and becaufe we know certainly of them, that they pafs by the centre of the Terrefirial Globe (being perpendicu- lar to its fuperficies, and not inclined ) therefore to conclude, it mufi be fuppofed, that the centre of the Earth is the I'ame with the centre of the World , or at lea ft , that the parts of the Fire and Earth defcend not, fa ve onely by one fole line which pciffeth by the centre of the World. Which neverthclefs is falfe, and re- pughant to experience , which ftieweth us , that the parts of Fire, not by one line onely, but by infinite, produced from the centre of the Earth towards all the parts of the World, afcend always by lines perpendicular to the Superficies of the Terrejtfei- al Globfe.

S alv. You do very ingenioufly h^d Anfiotle to the fame in- convenience, Sagredm J (hewing his manifeft equivoke j but withal you add another inconfiftency. We fee the Earth to be fpherical, and therefore are certain that it hath its centre, to which we fee all its parts are moved ^ forfo'we mnft fay, whilfi their motions are all perpendicular to the Superficies of the Earth h we

mean,

Images reproduced by courtesy of the Royal Library, Copenhagen.

2°K.B. 9,163

5

he

tvt lo^ ble, [fove- d to-

Ifrive

ts the 1 mo- wards : felf^ duced liac to Lunfc-

!Mtre : they idku- de, it with ? Fire jflfeth

M of

ii the fcend

sn-

9Ut

vhich their ) we

Dialogue. L

in-ean, that as they move to the centre of the Earth, they move t6 thnv IHoUy and to their Univerfal Mother : and we arc ftill far- ther fo free, that we will fufFer our felves to be perfwaded, that their natural inftinft is, not to go towards the centre of the Earth.

tind, or whether it be or no 3 and were it granted to be, it is but c.^.r. ./ th. an imagmary pomt, and a nothing without any quality. As to f,^^.'^' f^-""/^^' u^.at S..plm.s faid laft, that the contending Whether the parts ""^'^ thnfl n'^'^'' ^^^y^ feparated from their

h\^t^Z '"'u''''"^ ''^ " the cafe •

IS impoffible , It being clear by the Demonftrations of Anjiotle,

T/t T^'r ^f'' -^^pMc, impenetrable, unparta- W ./ 1 anlwer, that none of the conditions, whereby AriHo- ^kicb

tffo3:5:?.£' Co.left.al Bodie. from Elementary; hatho- tfter toundafon than what he deduceth from the diverfity of the n,c.arW.d.r.

affirmed tLt [tSfa,r"eT'^^^

is behoofull upon f cc'^ary confequence to fay, eitheTtha 'ehe attributes ot gencrable, onngenerable, alterable, or unalterable

^n" f^,°'LT"'^'''^'- ^I'^'^y «onIy agree with all worldly bodies, namely, as well to the Coelcftialas to the E- kmcntary i or that AriftotU hath badly and erroneoufly dcdu- leftial BodieT ' y\ach\it hath affigned to Coc-

on o^al?NI^'^T^'^ °[ "^g'^^^^io" ^^n^s to the fubverfi- of »ell *^^''°^°P''y' to the diforder and fubverfion

of Heaven and Earth, and the whole Univerfe ; but I beheve the Fundamentals of the f rrif .^.^zc^. are fuch , that we need not icar that new Sciences can be ereaed upon their ruines.

• L ^ r' ^^''^ "° thought in this place for Heaven or the Earth, neither fear their fubverfion, or the ruinc of Philofophy. As to nS'" ir"^ ^hat which you your felf hold

unalterable and nnpaffible ; as for the Earth, we ftrive to enoble and pcrfea it , whilft we make it like to the Coclcftial Bodies, and as It were place it in Heaven, whence your Philofophers have iSutes '[°^*'P''y f^lf <=annot but receive benefit from our n,.,^«,„w

H'uicsjior It our conceptions prove true, new Difcoverics will """r'i-aicm »/

Rath I'/ '""•■^ confirmed, .^^tj^^t"

M a Z^"""' y^""" '^are upon fome Philofophers, and help and ''""fi">f

AndfK ' *° ^"^"'^ '"^ ""no*^ improve.

wnat prelents it felf to you in confirmation of that great dif- crence which Arifiotle puts between theCocleftial Bodies, and fclcmcntary parts of the World, in making thofc ingenerable,

D incor-

Images reproduced by courtesy of the Royal Library, Copenhagen.

2°K.B. 9,163

z6 G, G A L 1 L ^ u bis SjlJeme.

incorruptible, unalterable,c^f . and this corruptible, alterable^c^r.

S iMPL» 1 fee not yet any need that AriftotU hath of help, ftandii\g as he doth ftoutly and ftrongly on his feet , yea not be- ing yet affaulted, much lefs foiled by you. And what ward will hx'Mtsdtfconrfe you choofe in this combate for this firft blow > Ari^iotle wrlteth, to prove the wcor- that whatevcr is generated, is made out of a contrary in fome ruptthtUtyofHe^' ^^j^j^^^ likewifc IS Corrupted in fome certain fubjecl from a generation & cor- contrary into a contrary , fo that (obferve) corruption and ge- ITi'^^^ trrti^', neration is never but onely in contraries ^ If therefore to a Coe- accord:»^ loArift! leftial Body no contrary can be affigned, for that to the circular To the circular motion 120 Other motion is contrary, then Nature hath done very motion no other ^akc that cxempt from contraries, which was to be in-

motion xscomrarj. incorruptiblcj This fundamental firft confirmed,

it immediately fqilowetli of confequence, that it is inaugmenta- ble, inalterable, impaflible, and finally eternal, and a propor- ^!ZJJ*lbel^' tionate habitation to the immortal Deities, conformable to the mortal God!. opinion even of all men that have any conceit of the Gods. He H^~JS/^^f^™^d^^^^^^ b^^enfe; in regard, that in all

fe^fe. times paft, acfor^iing to memory or tradition, we fee nothing re-

mov^a, according to the whole outward Heaven, nor any of its /r.pr.t..r^r^4t proper parts. Next, as to the circular motion, that no other is the circular motion contrary to xu Ari^iotle provcth many ways , but without reci. kath no contrary, ^j^^ ^hem all, it is fufficieutly dcmonftratcd, finccfimple motions are but three, to the medium^ from the medmnty and about the medium^ of which the two right, furfum and deorfum, are mani- feftly contrary h and becaufe one onely hath onely one for con- trary, therefore there refts no other motion which may be contra- ry to the circular. You fee the fubtle and moft concluding dif- courfe of AriftotU:, whereby he provcth the incorruptibihty of Heaven.

S A L V- This is nothing more, fave the pure progrefs of Arifto. tle^ by me hinted before h wherein, befides that I affirm, that the motion which you attribute to the Coeleftial Bodies agreeth alfo to the Earth, its illation proves nothing. I tell you therefore, that that circular motion which you affign to Coeleftial Bodies- fuiteth alfo to the Earth, from which, fuppofing that the reft of your difcourfe were concludent, will follow one of thefe three things, as I told you a little before, and fhall repeat^ namely, either that the Earth it felf is alfo ingenerable, and incorruptible, as the Coeleftial bodies^ or that the Coeleftial bodies are, like as the Elementary generabic, altemble &c. or that this difference of motion bath nothing to do with Generation and Corruption. The difcourfe of Arijiotle^ and yours alfo contain many Propofi- tions not to be lightly admitted, and the better to examine them, 1% will be convenient to reduce them to the moft abftrafted and

diftina

lOt be- d will riteth, Hbme wbm a id ge- i Coe- Tciriar e very be in- inned,

por- ro the s. He

of its

fer is frcci. tions lit the fcani- rcon- wjtra- ig dif- ey of

I and

Dialogue.^ I. ij difiinatlutcan bepolllblci and excufe me Sagredm, if haply with fome tcdioufnefs you hear me oft repeat the fame things, and fancie that you fee me reaffume my argument in the pub- liclc circle of Difputa tions. You fay Generation and Corrupti-

are onely amongft fimple natural bodies, moveable with contrary motions ; coatriry motions arc onely thofe which are made by a right line between contrary terms; and thefe are onely two, that IS to fay from the medium, and towards the mcdinm ; and mch motions belong to no other natural bodies, but to the Eartk

and r?' ' ^'^'"^'^^^ ^''"^fo^^ Generation

th.X aT'T " ^«*°"gft Elements. And becaufe

nc third fimple motion, namely, the circular about the vtcdinm,

onelv"L?hT"^' «^ contraries, and one

v^th whfch f body no con^arv^^^^^^ ^^"^^^ ^"""^'X ' having

th^?e is nT B^''"^- where

••"cre 19 no contrarietv thf *- ge*.^...^ ^ ^^^^ . ,

But fuch motion »"a^feo.dy with the CceleftTalSrehJ;: fore onely thefe are ingenerable, incorruptible, And to /'"-A^

begin I think ,t a more eafie thing, and fooner done to;^?olvl t^r'""^"'' whether the Earth (^a moft waft r^j„ Jf • • • . *"*^> '*'««^««r»wf'i'-

u ion about us own axis m twenty four hours would be, than it

g Silrco ^'^^ -'^"fa-^here befuch things a" KZ^ ' '°""P"°'' ^'"^ contrariety in nature. And if Lw

Zn lZnT r ""''" ""'^^'^ Nature obferves in w^ng,' When Ihe m a very ftort time begets an infinite number of flif from a httle vapour of the Muft of wine, and can fhew me which aldt"' '^rr'^fl'- r ^^'^ « - thatcorrSpte h,

I'tkZL^^""^'^ ''^'f ^"'^''^ '^'^ "'^^^ 'han I can ; for I Z Za! "T'^'*""?'"'^'"'' ^''^fe things. Bcfides, I would ve- fofa f^uf '^^"^^^"'^"'^-''y^heflcorruptivec^^^^^^ fo favourable to Daws, and fo cruel to Doves ; fo indulgent to

mofe've"a V" "°^^"> '^^y g""^ to them^nany

P. J. J 7 Jl^"' °^ i°«rniptibaity, than weeks to thefe.

reaches and Olives are planted in the fame foil, «pofed to the ^ me heat and cold, to the fame wind and rai>«s, and, in a word and thir "1^ contrarieties ; and yet thofe decay in a Ihort time* thoroww Z^^Tl ''""^"'^ y^"'- F"''hermore, I never was iL °S"^''fi^'l^boutthisfubftantiaI tranfmutation (ftiU keep-

tSa^^'ru"^''''^^^'''''''^'^ whereby a matter becometh fo Z fnrZ ' ^""'-^ be neceffarily faid to be deftroy'd, fo

nothmg remameth of its firft being, and that another body D a quite

Images reproduced by courtesy of the Royal Library, Copenhagen.

2°K.B. 9,163

[en

2g G. GALlLiEUS, fcfxSj/^^W^.

BrntrarWiionamt^ difFering therefrom fliould be thence produced ^ aixi If I ^ parts r^ayrtpre- r a bodv Under ouc afpeft, and by , and by under

W hd:es under ^ J ^ ..^ . i - i • • mUl^ U..^

MverfealyMs, ano

ther very different, 1 cannot think it impolTible but that it may

happen by a fimple tranfpofition of parts, without corrupting or ingendring any thing a-new , for we fee fuch kinds of Metamor- phofes dayly : fo that to return to my purpofe, I anfwer you, that inafmuch as you go about to perfwade me that the Earth cau not move circularly by way of corruptibility and generabihty, you have undertook a much harder task than 1 , that with argu- ments more difficult indeed, but nolefs concluding, will prove the contrary.

S AGR. Pardon mc, Sahiatus^ it I interrupt your difcourfe, which, as it delights me much, for that I alfo am graveled with the fame doubts , fo I fear that you can never conclude the fame, without altogether digrcfling from your chief defign : therefore if it be permitted to proceed in our firft argument, I fliould think that it were convenient to remit this queftion of generation and corruption to anotW dimndi and Tingle conference as alfo, if it fliaJI pleafc y^^ SimpliciHS, we may do by other particulac queftions which may fall in the way of our difcourfe h vi^hich I will keep in my mind to propofc, and cxaftly difcufs them fome other time. Now as for the prefent, fince you fay , that if Ari^ ffW^^ deny circular motion to the Earth in common with other bodies Caeleftial, it thence will follow, that the fame which be- falleth the Earth, as to its being generablc, alterable, will hold alfo of Heaven, let us enquire no further if there be fuch things in nature, as generation and corruption, or not ^ but let; us return to enquire what the Gtebe of the Earth doth.

S I M P L« I cannot fuffer my cars to hear it quetiion'd, whether generation and corruption bc in rcrnm natura^ it being a thing which we have continually before our eyes , and whereof A riftotU ^'^'yj^.'lll^^l hath written two whole Book^j But if you go about to deny the r« 'p^'^'^''^ Principles of Sciences, and queftion things moft manifeft , who may hmawtam- fcuows not, but that you may prave what you will, and maintain any Paradox ? And if you do not dayly fee herbs, plants, ani- mals to generate and corrupt, what is it that you do fee ? Alfo, do you not continually behold contrarieties contend together, and the Earth change into VVater^ the Water turn to Air, the Air into Fire, and again the Air to condenfc into Clouds, Rain^, Hails and Storms > /r/

SaGR. Yes, wc fee thefc thitigs indeed, and therefore will grant you the difcourfe of Arijlotle^ as to this part of generation and corruption made by contraries h but if 1 fliall conclude by virtue of the fame propofitions which are granted to Arifiotle, that the Coeleftial bodies themfelvcs are alfo generable and cor- ruptible

id.

Dialogue I*

^9

gdcr

for nor- ^u,

^an

ility, rgu-

Ith le,

Jforc think I and fo, if ^ulai lich I fomc Art^ other I be* will fuch it let

thing tftotU y the who ain mi- fo,

the

I will ation

the Elementary fay you h

what will you fay then

done that which is itnpoffible to

rupdble, afwell as SiMPL. I will be done.

SAGR. Go toi tell me, Simpltcim^ are not thefc afFeftions contrary to one another ? SIM PL. Which?

SAGR. Why thefc; Alterable, unalterable, pafflblc, ''impaf- *0'->l™P*^i^l«* fible^ generable, ingenerable, corruptible, incorruptible ? S I M p L. They are moft contrary.

S AGR. Well then, if this be true, and it be alfo granted, that Coeleftial Bodies are ingenerable and incorruptible; I prove that of neceffity Coeleftial Bodies muft be gcnerable and corru- ptible.

S I M P L* This muft needs be a Sophifm.

Sagr. Hear my Argument, and then cenfure and refolve it. ^^^^^-^i^^^^^^ Coeleftial Bodies, for that they are ingenerable and incorruptible,

are gcnerablt and

have in Nature their contraries, which are thofe Bodies that hc'orrupMe, hc-^

111 .1 caHie tnej are t»'

cTfrifrahi** r^t^A . L — ^^••'^ «s contrancty, there

therefore Coeleftial Bodies arc corrupt tbU,

gcnerable and corruptible - is alfo generatior. corruption ; gcnerable and corruptible.

S I MPi. Did 1 not fay it could be no other than a Sophifm > This is one of thofe forked Arguments called Sorita : like that The forked Syfb^ of the Cretan^ who faid that zWCretdus were lyars; but he aiss'M^^^'d:^,»}nf^ being a Cretan^ had told a lye, in faying that the Cretans were ly- ars ; it followed therefore, that the Crr^^j/rj' were no lyars, and confequently that he, as being a Cre^^j/i, had fpoke truth : And yet in faying the Cretans were lyacs, he had faid true, and com- prehending himfelf as a Cretan^ he muft confequently be a lyar. And thus in thefc kinds of Sopbifmssi man may dwell to eternity, and never come to any conclufion.

SagR. You have hitherto cen£urcd it, it tenuincth now that you anfwer it, (hewing the fallacie.

S I M p l: As to the refolving of it, and finding out its fallacie, do you not in the firft place fce a manifeft contradiflio^i in it ? Coeleftial Bodies are ingenerable and incorruptible ; E^i^i Ccelc- ftial Bodies are gcnerable and corruptible. And again, the gon- AmongfiCaUftiai trariety is not betwixt the Coeleftial Bodies, but betwixt the E- ^ ^

fcments, which have the contrariety of the MotionSj Jnrfkm and dc€rfhm, and of levity and gravity But the Heavens which move circularly, to which motion no other motion is contrary, want contrariety, and therefore they are incorruptible.

Sagr. Fair and foftly, SimplteiuS', this contrariety whereby you fay fome fimple Bodies become corruptible, refides it in the fame Body which is corrupted, or elfe hath it relation to fome o- Qther ? \ fay, for example, the humidity by which a piece of Earth

comrarttfjf.

IS

jQ C. G A L I L ^ u s, his Syfleme.

is corrupted, refidesitin the fame Earth or in fomc other bodie, which muft either be the Air or Water ? I beUeve you will grant, that like as the Motions upwards and downwards, and gravity and levity, which you make the firft contraries, cannot be in the fame Sub)ea,fo neither can moift and dry, hot and cold : you muft therefore confequently acknowledg that when abodic cor- Cntrariis .hich rupteth, it is occafioncd by fome quality rcfiding in another con- sre the cAufes of . therefore to make the Coeleftial Body become

corruptible, it fufficeth that there are in Nature, bodies that have dytkAtcorrHptcth, ^ contrariety to that Coeleftial body h and luch are the Elements, if it be true that corruptibility be contrary to incorruptibility.

Sim PL. This fufficeth not. Sir j The Elements alter and cor- rupt, becaufe they are intermixed, and are joyn'd to one another, Car/.y?«vi/W/« and fo may exercife their contrariety i but Coeleftial bodies are touch, but are not ff om the Elements, by which they are not fo much as

Tf^m^^ ^' toucht, though indeed they have an influence upon the Elements.

It is requifite, if you will prove generation and corruption in Coe- leftial bodies, that you fliciv j Chat there refides contrarieties be-

tween^hem.^^ how I will find thofe contrarieties between them. The firh fountain from whence you derive the contrariety of the Elements, is the contrariety of their motions upwards and down- wards it therefore is neceliary that thole Principles be in like Grdvity& levity, ^g^tiVi^i coutrarics to each other, upon which thole motions dc- fAritj and df^^Jj^^^ pend and bccaufe that is moveable upwards by hghtnefs, 4rf^c.«tMr7 ^j^.^ downwards by gravitv, it is nccelTary that lightnefs and

gravity are contrary to each other : no Icfs are we to believe thofe other Principles to be contraries, which are the caufes that this is heavy, and that light : but by your own confeffion, levity and gravity follow as confequents of rarity and denfity therefore r^./^,,«M./^ rarity and denfity fliall be contraries : the which conditions or fnrpafs the fmh^ afFeftions ate fo amply found in Coeleftial bodies, that you c- ^Helvfnt'delftf ftats to be oncly more denfc parts of their Heaven:

njttj. ^^^^ foUoweth that the denfity of the ftars exceeds

that of the reft of Heaven , by almoft infinite degrees : whichismanifeft,in that Heaven is infinitely tranfparent, and the ftars extremely opacous j and for that there arc there above no other qualities, but more and lefs denfity and rarity , which may be caufes of the greater or lefs tranfparency. There being then fuch contrariety between the Coeleftial bodies, it is necelfary that they alfobc generablc and corruptible, in the fame manner as the Elementary bodies arc h or clfe that contrariety is not the Rarity & derSttj caufc of Corruptibility, (^c.

inCeehf^iaibodies, § I M P L- There is no neceffity either of one or the other , for l^f'r^^^- that denfity and rarity in Cceleftial bodies, are not contraries to

each

Images reproduced by courtesy of the Royal Library, Copenhagen.

2°K.B. 9,163

Dialogue L"

3f

ant,

lie »u

ome have

€or- cuts.

1;^

s de- cnefs, s and thofe

rc

n$ or

each other, as in Elementary bodies i for that they depend not on the primary qualities, cold and heat, which are contrariesj but on the more or Icfs matter in proportion to quantity : now much and little, fpeak onely a relative oppofition, that is,. the. leaft of oppofitions, and which hath nothing to do with generation and corruption.

Sag R- Therefore affirming, that denfity and rarity, which a- mongft the Elements fhould be the caufe of gravity ^nd levity, which maybe the caufes of contrary motions furfkm and dear* fkm^ on which, again, dependeth the contrarieties for generation and cormption ^ it fufficeth not that they be thofe denfneffes and rareneffcs which under the fame quantity, or (if you will) mafs contain much or little matter, but it is neceifary that they be denf- neffes and rareneffes caufed by the primary qualities, hot and cold, otherwife they would operate nothing at all : but if this be fo, Ariflotle hath deceived us, for that he ftiould have told it us at Ariftode defeaive firft, and fo have left written that thofe fimple bodies are gene- 'LffjJh/ct

rable and corruptible tha;^ — "^^th {imple moiioDS ,»e„ts are gertera-

upwards and dow— dependent on levity and gravity, cau- I'i^ & crrr^p^M. fed by rarity and denfity, made by much or little matter , by reafon of heat and cold j and not to have ftaid at the fimple mo- tion furfum and deorfum : for I affure you that to the maidng of bodies heavy or light, whereby they come to be moved with contrary motions, any kind of denfity and rarity fufficeth, whe- ther it proceed from heat and cold, or what elfe you pleafc ^ for heat and cold have nothing to do in this affair : and you fhall upon experiment find, that a red hot iron, which you muft grant to have heat, weigheth as much, and moves in the fame manner as when it is cold. But to overpafs this alfo> how know you but that Coeleftial rarity and denfity depend on heat and cold ?

Sim PL. I know it, becaufe thofe qualities are not amongft Coeleftial bodies, which are neither hot nor cold.

S A L V- I fee wc arc again going about to cngulph our felves in a bottomlcfs ocean, where there is no getting to ftiore h this is a Navigation without Compafs, Stars, Oars or Rudder : fo that it will follow either that we be forced to pafs from Shelf to Shelf, or run on ground, or to fail continually in danger of being loft. Therefore, if according to your advice we fliall Proceed in our n^ain defign, wc muft of ncceffity for the preicnt overpafs this general confideration, wh^her direamotioP be neceffary in Na- ture, and agree with fome bodies and come to the particular demonftrations, obfervations and experiments h propounding in * the firft place all thofe that have been hitherto alledged by Arh ftotU, Ptolomey, and others, to prove the ftability of the Earth, en- deavouring in the next place toanfwer them : and producing m

the

Images reproduced by courtesy of the Royal Library, Copenhagen.

2°K.B. 9,163

p G. G A L I L ^ u s, Syjiane.

the laft place, thofe,by which others may be perfwaded, that the Earth is no lefs than the Moon, or any other Planet to be num- bered amongft natural bodies that move circularly.

SAGR. 1 fliall the more wiUmgly incline to this, in that I am better fatisfied with your Architeaonical and genera] difcourfe, than with that of ^r//^?f/e, for yours convinceth me without the leaftfcruple, and the other at every ftep croffcth my way with fome block. And 1 fee no rcafon why Simflicins Ihould not be prefently fatisfied with the Argument you alledg, to prove that there can be no fuch thing in nature as a motion by a right line, if we do but prefuppofe that the parts of the Univerfe are difpo- fed in an excellent conftitution and* perfeft order.

S A L V. Stay a little, good Sagredus^y for juft now a way comes into my mind, how I may give SimpliciHS fatisfaflion, provided that he will not be fo ftrifrly wedded to every expreflion of rifiotlcy as to hold it herefie to recede in any thing from him. Nor is there any queftion to be made, but that if we grant the excel- lent difpofitioii and pcif^a ord^r of the parts of the Univerfe, as to local fcituatkon, that then there is no other but the circular motion, and reft *, for as to the motion by a right line, I fee not how it can be of ufe for any thing, but to reduce to their natural conllitution, fome integral bodies that by fome accident were re-

, J feparated from their whole, as we laid above, ^^Lct us now confider the whole Terreftrial Globe, and enquire the beft we can, whether it, and the other Mundane bodies are to conferve themfelves in their perfefl: and natural difpofition. It isneceffary to fay, either that it reftsand keeps perpetually im- moveable in its place j or elfe that continuing always in its place, it revolves in irs felf i or that it turneth about a Centre, moving Arift.^ Ptolomey by the circumfcrence of a circle. Of which accidents, both Ari- fHiike the Ttrre- g^^/^ and Ftolomcyj and all their followers fay, that it hath ever z?,^,^^^^^^ and fhall continually keep the firft, that is, a perpetual

^7t is letter to f^y, tcft in the fame placc. Now, why, I pray you, ought they not thMttheferreftri- , r J J j-jjaj. jts natural afFcftion is to reft immoveable, vtl-

at Globe namr ally CO HdVe .»j i -i

reFieth, than that ther than to make natural unto it the motion * downwards, with it movethdireniy ^j^j^j^ jtiotion it ncver did or ihall move ? And as to the motion ^rhrword'is, by a right line, they muft grant us that Nature maketh ufe of it H'^y which the ^^^^5^ j-^^jj p^rts of the Earth, Water, Air, Fire, and every JicT™^^^^^ other integral Mundane body to their r/We, when any of them which is quke con- by chance are feparatcd, and fo tranfportcd out of their proper Ihorsfcnrc!^' ^" p'^^^ *' ^^^^ ^^^^h^ ^^^^ circular motion might not be found to be more convenient to make this reftitution. In my judg- ment, this primary pofition anfwers much better, even according to Ariftotles own method, to all the other confequcnccs , than to attribute the ftraight motion to be an intrinfick and natural

principle

D

I A LOG UE.

I.

iim-

lam

tiat

proper found judg. :ording , than natural

prinriple of tlic Elements. Which is manifeft , for that if I aske

the Pe

that Coeleftial bodies are

tpateticf^^j it, being or opinion 1 incorruptibe and eternal , he believeth that the Terreftial Globe is not fo , but corruptible and mortal , fo that there (hall come a lime , when the Sun and Moon and other Stars , continuing their beings and operations , the Earth (hall not be found in the World 5 but (hall with the reft of the Elements be deftroyed and annihilated, I am certain that he would anfwer me, no: therefore grencration and corruption is in the parts and not in the Oi€othn whole 5 and in the parts very fmall and iuperhciai , which are, attributed to the. as it were , incenfible in comparifon of the whole malTe. And ^^y]^ ^^^^^^^^^^^ becaufe Ariftotle deduceth generation and corruption from the ^ ^ contrariety of ftreight motions , let us remit fuch motions to the parts , which onely change and decay , and to the whole Globe and Sphere of the Elements , let us afcribe either the circular mo- tion , or a perpetual coii(]ftance in its proper place : the only affeftions apt for perpetuation , and maintaining of perfeft order. This which is fpokcn of the Earth . may te faid with the fame leafonof Fire., and S^^^^^^ P^" ^''^ ' which

Elements the r^^ipateticl^s are forced to afcribe for intrinffcal T** ^^^'p^t^tickj

and natural , a motion wherewith they were never yet moved, ^thiP'mlth£% nor never fliall be , and to call that motion preternatural to them, Elements for wherewith, if they move at all , they do and ever fliall move. ^hLTLy ncvt This I fay , becaufe they a(rign to the Air aud Fire the motion were moved, and upwards , wherewith thofe Elements were never moved , but \ Jtlr^aiwithZM only fome parts of them , and thofe were fo moved onely in or- they aiwajes are der to the recovery of their perfeft conftitution , when they were out of their natural places ^ and on the contrary they call the circular motion preternatural to them , though they are thereby inceffantly moved : forgeting, as it feemeth, what Arijietle oft in- culcateth, that nothing violent can be permanent.

S I M p L- To all thefe we have very pertinent anfwers , which Se^jibu experh . Ifor this time omit, that we may come to the more particular ^^^'f^^A^,^^^ reafons , and fenfible experiments , which ought in conclufion to ArgJmmH""^'^^ beoppofed, as Arijiotlefmh well, to whatever humane reafon can prefect us with.

Sagr. What hath beenfpoken hitherto, ferves to clear up unto us which of the two general difcourfes carrieth with it moft of probability, 1 mean that of y^ri/ia^/e , which ^ould perfwade ^s>that the fublunary bodies are by nature gen^rable, and corru- ptible, i^c. and therefore moft different from the eifence of Coe- leftial bodies , which are impafTible , ingenerable, incorruptible, drawn from the diverfity of fimple motions j or elfe this of Sahiatus^ who fuppofing the integral parts of the World to be ^fpoled in ^ perfcft conftitution , excludes by ^neceffary confe-

E quence

2^ G. GALiLJEUSyhis Sylleme.

quence the right or ftraight motion of limple natural bodies, as being of no ufe in nature, and efteems the Earth it fclf aUo to be one of the Cctleftial bodies adorn d with all the prerogatives that agiec with them j which laft difcourfe is hitherto much move likely, in my judgment, than that other. Therefore re- folve, Simflictus-, to produce all the particular reafons, experi- ments and obfcrvations, as well Natural as Aftronomical, that may ferve to peifwadc us that the Earth differcth from the Coc- leftial bodies, is immoveable, and fituated in the Centre of the World, and what ever elfe excludes its moving like to the Planets, as Jupiter or the Mooji^ And Sal^iatns will be plealed to

be fo civil as to anfwer to them one by one.

S I M P L. See here for a begining, two moft convincing Argu- ments to dcmonftrate the Earth to be moft different from the Coeleftial bodies. Firft, the bodies that are gcnerable, corru- ptible, alterable, C^f. are quite different from thole that are in- generable, incorruptible, unalterable, &*c. But the Earth is ge- nerable, corruptible, alterable^, e^r. and the Coeleftial bodies in- generable, iflcorruptible, unalterable, &^c. Therefore the Earth IS quite diflEerent from the Coeleftial bodie?.

S A G R. By your firft Argument you fpread the Table with the fame Viands, which but juft now with much adoe were voided.

SiMPL. tl^^^ ^ ^^^^ ^'^"8 ^i^li you,

and then tell me if this be not different from what you had be- fore . I" the former, the Minor was proved a prior i^Sc now you fee it proved a poftertori : Judg then if it be the fame. I prove the Mi/^^r^thereforc (the Major being moft manifeft J by fenfible ex- perience, which fhews us that in the Earth there are made conti- nual generations, corruptions, alterations, c>c. which neither our ien£cs, nor the traditions or memories of our Anccftors, ever faw an inftance of in Heaven ^ therefore Heaven is unalterable, ffeaven imtnuU' Earth alterable, ^r. and therefore different from Hea-

lt)rZtytZ ven. I take my fecond Argument from a principal and effential ration feen in it. accident , and it is this. That body which is by its nature ob- Bodiet naturally fcute and deprived of light , Is divers from the luminous and fhi- lucid, are df event . , ^j^^ £^j.th is obfcute and void of light , and the

from thoje tvhtch uuun-*^ i i j. i J r 11 r r i i? ^

are hj nature ob- Coelcftial bodics fplcndid , and tuU ot light j Lrgo-, &c. Anfwer to thefe Arguments firft , that we may not heap up too many, and then 1 will alledge others.

S ALV- As to the firft-, the ftreffc whereof you lay upon ex- perience, I defire that you would a little more diftinftly produce me the alteration which you fee made in the Earth, and not in Heaven ■, upon which you call the Earth alterable, and the Hea- vens not fo.

S I M P L- I in the Earth, plants and animals continually ge- nerating

Dl A LOG UE.

I.

35

Lies m- larth

the

: conti- her our .^er faw

m Hea- rlTential MC ob-

and the Anfwer > many,

pon ex- 5roduce 1 not in lie Hea-

ii

lerating

nerating and decaying h winds, rains, tcmpefts, ftorms anfing ; and in a word, the afpea of the Earth to be perpetually metamorpho- fing none of which mutations arc to be difcern d in the Cceleftial bodies j the conftitution and figuration of which is moft punSu- ally conformable to that they ever were time out of mind^ without the generation of any thing that is new , or corruption of any thing that was old.

S \ L But if you content your felf with thefe vifible , or to fay better , feen experiments , you muft confequently account Chinorrgtnd America Coeleftial bodies, for doubtleffe you never beheld in them thefe alterations which you fee here in Italy , and that therefore according to your apprehenfion they are inal- terable-

Sim PL. Though I never did fee thefe alterations fenfibly in

thofe pUcQs , the relations of them are not to be queftioned i

befides that , cum eadem ft ratio tot ins -i ^ fartium y thofe

Countreys being a part of the Earth 5 as well as ours , they

muft of neceflity be alterable as thefe are.

S a l v. And why hav^ >-7 ' TTr"' ^Tl ' other mens xelations , exammcd and obterved thofe altcrationi

with your own eyes ?

S I MPL- Becaufe thofe places , befides that they are not ex- pofed to our eyes , are fo remote , that our fight cannot reach to comprehend therein fuch like mutations.

S A L V, See now, how you have unawares difcovered the falla- cy of your Argument , for, if you fay that the alterations that are feen on the Earth neet at hand, cannot, by reafon of the too great diftance,be feen in America , much lelTe can you fee them in the Moon , which is fo many hundred times more remote : And if you believe the alterations in Mexico upon the report of thofe that come from thence , what intelligence have you from the Moon , to affure you that there is no fuch alterations in it > Therefore, from your not feeing any alterations in Heaven, whereas, if there were any fuch , you could not fee them by rea- fon of their too great diftance , and from your not having intel- ligence thereof , in regard that it cannot be had , you ought not to argue , that there arc no fuch alterations , howbeit,from the feeing and obferving of them on Earth , you well argue that therein fuch there arc. • • i r

Simp i.. I will (hew 10 great mutations tb^t have befaln on ^l^c Earth , that if any fuch had happened in the Moon , they miglu very well have been obferved here below. We find in very ancient records , that heretofore at the Streights of Gibraltar, the two gicat Mountains Abila, and Calpen, were continued td- ./ Ai.-, getherby certaia other Icffe Mountains , which there gave check

E 2

G. G A L 1 L u bis SyfJeme.

to the Oceaii; : but thofe Hills , being by fome caufc or other fe- paratcd, and a way being opened for the Sea to break irt^it made fuch an inundation) that it gave occafion to the calling of it fince the Midland Sea : the greatnefs whereof confidered, and the di- vers afpeSs the furfaces of the Water and Earth then made 5 had it beeti beheld afar off, there is no doubt but fo great a change might have been difcerned by one that was tlien in the Moon ; as alfo to us inhabitants of the Earth, the like alterations would be perceived in the Moon j but we find not in antiquity, that ver there was fuch a thipg feen h therefore We have n6f Caufe td fay, that any of the Coeleftial bodies are alterable,

Salv- That fo great alterations havehapned in the^IVtdon, I dare not fay, but for all that, I am not yet cerrain but that fuch changes might occurs and becaufe fuch a mutation could onely Teprefent4into us fome kind of variation between the m6re clear, and more obfcure parts of the Moon, I know not whether we have had Oil Earth obfervant SelenograjJiets, who have for any confiderable number of years, inftruSed us with fo exaft Seleno- graphy, as that we ftould confidently coi^elude, that there hath no fuch change hapned in the face of the Moon i of the figura- tion of which I find no more particular defcription, than the fay- ing of fome, that it reprefents an humarie face h of others, that it is like the mnzU of a Lyon j and of others, that it is Cain with a bundle of thorns on his back : therefore, to fay Heaven is un- alteriiblc^becauferhat in the Moon, or other Coeleftial bodies, no fuch alterations are feen, as difcover themfelves on Earth, is a bad illatidb, and concludeth nothing.

S A G R- And there is another odd kind of fcruple in this Argu- ment of Simpltcit0^ running in nfiy mind, which I would gladly have anfwered j therefore I demand of him, whether the Earth before thcMeditcrranian inundation was generable and corrupti- ble, or elfe began then fo to be ?

Sim PL* It wasdoubtlefs generable and corruptible alfo be- fore that time ; but that was fo vaft a mutation , that it might have been obferved as far as the Moon.

Sa gR. Go to^ if the Earth was generable and corruptible before that Inundation , why may not the Moon be fo like- wife without fuch a change > Or why (hould that be neceffary in the Moon, which importeth nothing on Earth >

Salv- It isaflirewd queftion : ButI am doubtfull that Sim^ flicim a Httle altercth the Text of Arijiotle^ and the other Peri- pateticl{s^ who fay, they hold the Heavens unalterable, for that they fee therein no one ftar generate or corrupt, which is proba- bly a lefs part of Heaven, than a City is of the Earth , and yet innumerable of thefe have been deftroyed, fo as that no mark of them hath remainU S a G R-

^Argii-

gladly Earth

rrupn-

Dialogue!. 57

^ A GR' r verily believed ocherwife, and conceited thatiyi;^- plhcins d'lffemhhd this expofition of the Text^ that he might not charge his Matter and Confeaators, with a notion more abiurd than the foniier. And what a folly it is to' fky the Coclcftial part is unalterable, becaufe noftars^ do generate or corrupt there- in? What then? hath aiiy one feen a Terreftrial Globe corrupt^and another regenerate in its place? And yet is it not on aft hands granted by Fhilofophers, that there are very few ftars i^Plfeav^A lefe than the Earth, but very many that aipe^much bigger^? So that for a ftar in Heaven to corrupt, would be fiolefs. than if. the luJoJt fi!r tl whole Terreftrial Globe fbould be deftroy'd. There fore^ if for <^o^ri*pt , than for the true proof of generation and corruption in^ the Univerfi?, it be ^alcioh^^^'^'' neceffary that i'o vaft bodies as a ftar, muft corrupt and regene- rate, you may fatisfie your felf and ceafe your opinion *, for I affare you, that you fliall never fee the Terreftrial Glote- or any other integral body oiF the World, to corrupt ot decay fo, tfiat having been beheld by us for fo many years paft, they (hould fo diffolve, as not to leave any foot^^'^i^s of ck<^

S/vLv. But to oiv^ ^^fficim yet fuHer f^ri^aak>«, ar^d to reclaim him, i^* f^^I^' f^^"^ his error 5 I affirm, that we have ?A ottr age new accidents and obfervations, andfuch, that I queftion chL^fht^Thn not in the leaft, but if Arijiotle were now alive, they would naakd duil fel IheTo- him change his opinion 5 which riiay be eafily colleflted from the '^'^^^'^^f^^rage. very manner of his difcourfing For -when he writeth th^it he e- fteemeth the Heavens inalterable,' '&c. becaufe no new thing was feen to be begot therein, or any old to be diflblved, he feems im- plicitely to hmt unto us, that when ce (hould fee any fuch acci- dent, he would hold the contrary , and confront, as indeed it is meet, fenfible experiments to natural reafoii : for had he not made any reckoning of the fenfes, he would not then from the not feeing of any fenfible mutation, have argued immutability.

SiMPL- Arijiotle deduceth his principal Argument a friori^ Ihewing the neccflity of the inalterability of Heaven by natural, manifeft and clear principles j and then ftabliflieth the fame a po^ fieriori, by fenfe, and the traditions of the antients.

Salv. This you fpeak of is the Method he hath obferved in delivering his Doarine , buf I do not bethink it yet to be that wherewith he invented it h for I do believe for certain , that he firft procured by help of the fenfes , fuch experiments and obfer- Nations as he couldjto afTure him as much as it was po{rible,of the The certainty of c^ncluaon , and that he afterwards fought out the means how to ^^' cond^.^^nhei' uemonltrate it : For this is the ufual courfe in demonftrative Scien- method to find the ces , and the reafon thereof is , becaufe when the conclufion is dcmo^sirathH. true, by help of refolutive Method, one may hit upon fome pro- pofition before dcmonftrated , or come to fome principle known

Images reproduced by courtesy of the Royal Library, Copenhagen.

2°K.B. 9,163

38

G. G A L I L * u s, hit Syfieme:

butiftheconclufionbefalfe, a man may proceed i« i«- fjr fe , ^^^^^eetwithany truth already known butve-

^" He fl«ll meet with fomc impoffibiUty or manifeft abfurdi-

P,.H,,ons.j../,^; Nor need you queftion but that ^'^'^Jf --V^-g « H«4«J /.r i; ri ihe demonftration for which he offered the Hecar .G«v./i«- fore he found . ,j..r„uare of the fide lubtendin^

,n..ilr.M,ch tomb , had been certain, that the iquare oi inc i „ '"f""'^ the right angle in a re6tangle triangle , was equal to the Iqu^re ol therigncangi .^nd the certainty of the conclufion condu-

'^rnt'Xl to\he iTve^^^^^^ ot\he demonftration, un, ^ (vTndi^e me Ilwayes to mean in demonftrative Science.. Bu^ what et waT heiJhodof A.fiotle and whether his arguingi rprrdedfenfe a poftermi , or the contrary iit fufficeth that K 7 ^T^fttrpreferrith (as hath been oft laid) fenfible- ex- ^»Ss b£ea&^^ befides, as to the\rugments i E Aeir force hath been aheady examined. Now returning Lmv Purpofcd matter, Ifay, that the things in our times dif^ covered in the Heavcns,are, and have been fuch , that they may oive abfolute fatisfaaion to all Phi ofophers , forafmuch as m S • 1 and in the univcrfalcxpanfion of Heaven,

t fi« Sd are continually, feen juS fuch accidents a. t^ciHene ^aonsand corrMptions , being that excellent A- we g uc^^^^A inanv Comets generated and diflTolved

ftronomcrs have obfervc^^^^^^ ^J^^^ ^^^^^^ ^^^^^^^^^

in parts hig ^^^^ ^^^^ ^ without contradiaion much higher " *,?4e Planets i and in the face of the Sun it felf , by help Zl'^'^ th. -^^^^^^^ certain denfe and obfcurefubftances, in fem.

%"dX'b>f'c. j^j^^^^ like to the foggs »bout the Earth, are feen to be produced and dilTolved •, and many of thefe are fo vaft, that thev far exceed not only the Mediterranian Streight , but all

s.ur S}.s Jjlica^nd Afia^Ko. Now if ^njio./e had feen theft things,

g;;Z»-«A-XtthinkyouhewouIdhavefaid, and done ?

A AflrKk. ^''f 77 \ k„ow not what Arifiotle would have done or faid, that was the great Mafter of all the Sciences , but yet I ktiow in part what his Sedators do and fay , and ought to do and fay unleffethey would deprive themfelvesof their guide leader, and unieue tncy As to the Comets, are not thofe Modern

Snl^ w^^^^^^ them Ccleftial, convinced by

Altronomc. , ^ overcome with their own weapons, I

concluding It the laft in favour of ArM , that they are all Elementary > And this being overthrown, which was as u were their foundation, have thefe Novellifts any thing more where- J with to maintain their a{fcrtion ? >S Salv. Hold a little, apod Simphaus , this modern Author, ^ what faith heto the new Stars , Anno 1 5 /a, and 1 604 , and to 1

D

I A L O G U E

I.

39

it- it ve-

P>e>

leca-

tot

. But Liingi h that Ic* ex- ^rvts i ping

W

Even, :nts as :nt A- ffolved J Stars, higher •y help m fern- I to be , that but all

iiungs, ^faid, 5W in tid fay, ier, and iodern d by pons, I ^tryed, ire all pwere ■fhere-

Kuthor, and to the

the Solar fpots ? for as to the Comets , 1 for my own particular little care to make them generated under or above the Moonj nor did I ever put much ftreffe on the loquacity of Tycho j nor am I hard to believe that their matter is Elementary , and that they may elevate (fubhmate) themfelves at their pleafure, with- out meeting with any obftacle from the impenetrabiUty of the Penpatetul^ Heaven 5 which I hold to be far more thin, yielding, and fubtil than our Air j and as to the calculations of the Pa- rallaxes, -firft, the uncertainty whether Comets are fub)e£i: to fuch accidents, and next , the inconftancy of the obfervations, upon which the computations are made, make me equally fuf- peft both thofe opinions : and the rather , for that I fee him Anti-Tycho me- you call Ami'Tychoy fome times ft retch to his purpofe , or clfe rcjeft thofe obfervadons which interfere with his defiffti. ol,f.rv«.o.< his

oiMP.L. As to the new Stars ^ Anti-Tycho extricates mmieli ^My. in three or four words , faying, That thofe mo- dern new Stars are no certain parts of the CoclcftiaJ bodies , and that the adverfaries , if they will prove alteration and genera- tion in thofe iuperior l^^-^"' muft ihcw f^^^ ««utAtions that have been made «^ the Stars defcribed fo many ages paft, of which F^r« is no doubt but that they be Coelcftial bodies ^ which they c^in never be able to do : Next, as to thofe mat- ters which fome affirm, to generate and diffipate in the face of the Sun, he makes no mention thereof ^ wherefore 1 conclude, that he believed them fiftious , or the illufions of the Tube, or at raoft, fome petty efFefo caufed by the Air, and in brief, any thing rather than matters Coeleftial.

S ALv. But yow^ Simplicim-i what anfwer could you give to the oppofition of thefe importunate fpots which arc ftarted up to difturb the Heavens, and more than that, the Ferzpatetick^ Philofophy ? It cannot be but that you, who are fo refolute a Champion of it , have found fome reply or folution for the fame, of whi^li you ought not to deprive us.

SiMPL. I have heard fundry opinions about this particular. One faith ; " They are Stars which in their proper Orbs, like as yenus and Mern/rj^, revolve about the Sun, and in paffing un- touchll^CsoZ der it, rcprefent themfelves to us obfcure ; and for that they ''are many, tbey oft happen to aggregate their parts together, '^^and afterwards feperate again. Others believe them to be ''aerial impreffions h others, the illufions of the chryftals j and o- thcrs, other things : But 1 incline to think, yea am verily per- 'iw^ded, That they are an apgrcgate af many feveral opacous

c] A' ' " """-^ aggregate many leverai opacous

^1 bodies, as it were cafually concurrent among themfelves. And therefore we often fee , that in one of thofe fpots one may number ten or more fuch fniall bodies . which are of irregu-

"lar

^' lar figures , and feem to us like flakes of fnow , or flocks of " wooll, or moaths flying : they vary fite amongfl: themfelves, and one while fever, another while meet, and mofl of all be- "neath the Sun, about which, as about their Centre, they con- t'tinually move. But yet, muft we not therefore grant, that they are generated or dilfolved , but that atfometimes they are hid behind the body of the Sun , and at other times , though remote from it, yet are they not feen for the vicinity of the immeafurable light of the Sun j in regard that in the cccentrick Orb of the Sun , there is conflituted, as it were, an Onion, corn- ed pofed of many folds one within another , each of which, being * The Original " ftudded with certain fmall fpots , doth move ^ and albeit their h\ih\temfeflMa ft cc motion at firfl: feemeth inconfl:ant and irregular , yet neverthe-

tnmve] which the , rr_ r<^\A it lalV . to be obfprvpd fKif rlip vprv fame fonfc

^'"rr-'-r luUHUH At iii*^ tj ^ J

] which the np itisfaidatlaft, to be obferved that the very fame fpots, on , ( miftaking cc before , do withm a aeterminate time return agam. This

.1 ^ . ^l.^ Ct't-^n*^ '\r\\\\Tf>r V«»M^ (-t^ttt^ ^ .

rfwp^/?4M,aword to me the fittefl: anfwer that hath been found to afligne

remfeftallS ^^""Z a rcafon of tjiat fame appearance , and withal to maintain the dercth [ incotrupt ability and ingenerabihty of the Heavens ^ and if this iTgXhlviol"^^ there wants not more elevated wits , which will

tranfportmeut , as other, tnore convincing.

a'shf'""''^" Salv- If this of which we difpute , were feme point of Law, /„ nati^Mi Sci' or other part of the Studies called Humanity , wherein there is e^ces, the art of ^^j^j^^^ ^^^^i^ nor falOiood , if wc will give fufficient credit to forty " the acutenefle of the wit, readinefleof anfwers, and the gene- ral praftice of Writers , then he who moft aboundeth in thefe, makes his reafon more probable and plaufible ^ but in Nat^ural Sciences , the cone lufions of which are true and neceflary , and wherewith the judgment of men hath nothing to do , one is to be more cautious how he goeth about to maintain anything that is falfe 5 for a man but of an ordinary wit , if it be his good for- tune to be of the right fide , may lay a thoufand Demofihcnes and a thoufand Ariftotles at his feet. Therefore rejeft thofe hopes and conceits, wherewith you flatter your felf, tbat there can be any men fo much more learned , read , and verfed in Authors, than we ? that in defpite of nature , they ftiould be able to make that become true , which is falfe. And feeing that of all the opinions that have been hitherto alledged touching the ef- fence of thefe Solar fpots , this inftanced In by you , is in your judgment the truefl: , it followeth (if this be fo) that all the reft are falfe h and to deliver you from this alfo , which doubtlefle is a moft falfe Chimcera , over-pafling infinite other improbabihties that are therein , I (hall propofe againfl: it onely two experiments-, j4n AriumeM jg ^ that many of thofe fpots arc feen to arife in the midft of fZethThl^ZiIr the Solar ring , and many likewife to diflblve and vanifli at a great fpots to ^^wr'*^* difl;ance from the circumference of the Sun, aneceffary Argu-

.^nd dijfolve, jj^^j^j.

D

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41

cks of selves, 11 be- r con-

that ey are hough )f the 'ntrick , corn- being it their rerthe- fpots,

This affigne un the if this |will

f Law,

;here is edit to - gene- i thefe, ^at^ural y, and [le is to ig that ad for- nes and

^pes I be ithdrs , Mc to m all peef- in your the reft ■Teisa roilities itnents*, l^of Igreat { Argu- ment

and diffolve ^ for if without gc

A conclufivt de»

It

ment that they generate

or corrrupting, they fliould appear there by onely local motion, thev would all be feen to enter, and pals out by the extreme cir- cumference. The other oblervatron to inch as are not lituate m ^j„jirmoH, that the lowcft degree ofienorancc in PerfpeSive, by the mutation t^^i/^^^^ ^rjc.^tir- of the appearing figures, and by the apparent mutations ot tlie ^^^^^^ velocity of motion is neceffarily concluding , that the fpots are contiguous to the body of the Sun, and that touching its fupcrfi- cies, thsy move either with it or upon it, and that they in na wife m6vc in circles remote from the fame. The motion proves The motion of the

which towards the circumference of the Solar Circle , appeareth very flow, and towards the midft, more fwift ^ the the s»» apfsars gures of the fpots confirmeth it, which towards the circumference appear exceeding narrow in comparifon of that which they feem ff^ts avfears nar- to be in the parts nearer the middle i and this becaufe in the ro^ towards the midft they are feen in their fulllufter, and as they truly be, ana thesnnsd:ikvi^,^, towards the circumference by reafon of the convexity of the glo* n?^;. bous fuperficies, they feem more compreff'd : And both thefe diminutions of figure and it»--— ^^^^^ ^"ow how to obfcrve and calculate thcmc^aaiy, prccifely anfwet to that which ftould appear, the fpots being contiguous to the Sun, and difter irrecon- cilcably from a motion in circles remote, though but for fmal intervalls from the body of the Sun--, as hath been difFufcly de- ^^^^^^^^^.^^^^^ monftrated by our Friepd, in his Letters about the Solar fpots,

fr/Wi as alfochat

to Marcus Velfttm. ^ It may'W gathered from the fame muta- ^^^f^'^f'^'^^^^^ tion of figure^ that none of 'them are ftars, or other bodies of modcftiy* fpherical figure i for that amonaft all figures the fphere never conceais himfeif

f .0 • ^, r^JU-T T throughout theic

appeareth comprelTcd, nor can ever be reprdented but onely per-* j;)iayogues. f^ly round 3 and thus in cafe any patticular fpot were a round body, as all the ftiUrs aw held to be, the faid roundnrfa would as wfell appear in the midft bf the Solar ring, as when the fpot is near the extreine : whercas) itsfo great compreflion, and fliev^ing its felffofm^ill toward^ dke^sxtreme^ and contrariwife, fpatious and ki'ge towairdsthe itiiddle, a (Tare th us , that thefe fpots are flat SoUrfiots plates of fmall thicknefo or depths in comparifon of their length are Lt "fphencai, and breadth; Laftly, whereas you fay that the fpots after their i'^'jtjat itke thin deter mmate periods ar^ obferved t<» return to their former alpeft, believe it not, SimpUcins^ for he that told you fo, will deceive you i and that 1 fpeak the truth, you may obferve them to be hid in the face of the Sun far from the circumference ^ nor hath your ^bfervator told you a word of that compretf^on, which necefTa- rily ^rgucth them to be contiguous to the Sun. That which he tells you of the return of the faid fpots, is nothing elfe but what is read in the forementioned Letters, namely, that fome of them may fometimes fo happen that are of fo long a duration? that

F they

42 G. G A L I L i?: u s, his Syjleme.

they cannot be diffipated by one folc converfion about the Sun, which is accompliflied in lefs than a moncth.

Sim PL- h for my part, have not made either fo long, or fo exaft obfervations, as to enable me to boaft my felf Mafter of the Quod eii of this matter : but I will more accurately confidcr the fame, and make tryal my felf for my own fatisfaSion, whether I can reconcile that which experience (hews us, with that which Arijiotle teachethus , for it's a certain Maxim, that two Truths cannot be contrary to one another.

Salv« If you would reconcile that which fenfe flieweth you, OnecAnm (faith ^^^^ the foUdcr Doftrines of Arijlothy you will find no great dif- Aiiftocle) i?^4iLficulty in the undertakings and that fo it is, doth not ArifiotU vefft^reafi^^^ ^h^t onc cannot treat confidently of the things of Heaven, 'it$\reatdtfiance, by rcafon of their great remotcnefs ?

S I M P L. He exprefly faith fo. hu({oi\<tpTifers S AL V- And doth he not likewife affirm, that we ought to pre- fenfe Before ratio- jfer that which fcufc demouftrates, before all Arguments, though etnatton. appearance never fo well grounded ? and faith he not this

• without the leaft doubt or hacfitation ?

SiMPL. He doth fo. ^ S AxV* Why then, the fccond of thefe propofitions, which ar^ Jtsadottrinemote^^^^ doftrfnc of AriftotU:, that faiths that fenfe is to take s^eeing Zith A- place of Logick, is a dodrine much more folid and undoubted, nftotlc. to fay the ^^^^ ^\^^t Other which holdeth the Hea^ns to be unalterable • and ^^"Xrfrr therefore you fliall argue more jAfiotdicaUy, faying, the Hea- rphich affirms yens irc alterable, for that fo my fenfe telleth me, than if you them inalterable, ^^^j j f^y^ ^hc Hcavcns are u alterable, for that Logick fo perfwa- AW f AriBotle. Furthermore, we may difcourfe of Cacleftial mat- Tdefcope V- ^^^^ ^^^^ ^'^^f' ^ri/i(^//e ; becaufe, he confeffing the know-

courfe Better efcoe- Icdg thereof to be difficult to him, by reafon of their remotcnefs ifJnLCTm' ^'""^ ^^^^^'^ ^^^''^^y acknowledgeth, that one to whom felf. the fenfes can better rcprefent the fame, may philofophatc upon

them with more certainty. Now we by help of the Telefcope, are brought thirty or forty times nearer to the Heavens, than ever Arijiotle came j fo that we may difcover in them an hundred things, which he could not fee, and amongft the rejft, thefe fpots in the Sun, which were to him abfolutcly invifible i therefore wc may difcourfe of the Heavens and Sun, with more certainty than Ariftolte.

S A G R. 1 fee into the heart of Stmplucius^ and know that he is much moved at the ftrength of thefe fo convincing Arguments j but on the other fide, when he confidereth the great authority which Arijiotle hath won with all men, and remembreth the great number of famous Interpreters, which have made it their bufinefs to explain his fenfe ^ and fccth other Sciences^ fo ncceffary and

profitable

D

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I.

Sun,

you, tSLt dif- IriflotU caveuj

I pre- :)ugh this

iich are to take aubted, and ^Hea- if you perfwa- ial mat- ; know- lotenefs whom c upon efcope, in ever iUndred fe fpots ereforc tainty

W]

he is nents ; thority e great ufinefs ry and "table

profitable to the publick, to build a great part of their efteem

puzzled and

45

and

L the credit of

ireputati ^

perplexed : and methinks I hear him fay, To whom then fliould neD^cUmathn we repair for the decifion of our controverfies, if Jnpotle were ^/SimpHcius. removed from the chair? What other Author ftiould we follow in the Schools, Academies and Studies ? What Philofopher hath writ all the parts of Natural Philofophy, and that fo methodically without omitting fo much as one finglc conclufion > Shall we then overthrow that Fabrick under which fo many pafTengers find flielter ? Shall we deftroy that Jfylum, that Prytaneum, where- in lo many Students meet with commodious harbour , where without expoling themfelves to the injuries of the air, with the oneJy turning over of a few leaves, one may learn all the fe- crets of. Nature? Shall we difmantle that fort in which we are late trom all hoftile aflaults ? But I pitie him no more than I do that Gentleman who with great expence of time and treafurcj and the help of many hundred artifts , e reds a very fumptu- ous Pallace, and afterwards beholds it ready to fall, byreafoa ot the bad foundation : ^^'"B extrc.«^jy ^^^aiing to fee the Walls ilript which are adorned with fo many beautiful! Piaurcs i or to fulFer the columns to fall, that uphold the {late- ly Galleries ; or the gilded roofs ^ chimney-pieces , the freizcs the cornilhes of marble, with fo much coft erefied, to be rui! ned 3 gocth about with girders, props, (hoars, butteraifes, to pre*, vent their fubverfion. t

S ALv. But alafs, Simplicius as yet fears no fuch fall, and 1 would undertake to fecure him from that mifchief at a far leis charge. There is no danger that fo great a multitude o£ "P^ipdtctick.Phi- w i ^"""^ wiJ'e Philofophers, Oiould fufFer themfelves to be I'^^f^ tietlor d by one or two, who make a little bluftering i nay, they will rather , without ever turning the points of their pens ^gainft tliem , by their filence oncly render them the objea of univcrfal fcorn and contempt. It is a fond conceit for any one to think to introduce new Philofophy, by reproving this or that Author : it will be firft necefTary to new-mold the brains of men, and make them apt to diftinguift truth from falfliood. a tning which onely God can do. But from one difcourfe to another ^hither are we ftray d } your memory mull help to guide me into ^he way again.

^iMPL. I remember very well where we left. We were

^P^n the anfwcr of Anti-Tycho y to the objeQions againft the

o?^r^^'''^^ of the Heavens, among which you inferted this

i !^ A^^^^ ^^^^^ ' ^ believe you

ntended to examine his anfwer to the inllance of the New ^tars. , ,

F 2

44 G. G A L 1 L u S;, bis Sjflme.

Sa-LV- Now 1 remember the reft, and to proceed, Methinks there are fome things in the anfwcr of Anti-Tycho^ worthy of reprehenfion. Andfirft, if the two New Stars, which he can do no lefs than place in the uppermoft parts of the Heavens , and which' were bf a long duration, but finally vanifhed, give him no dbftruftion in maintaining the inalterability of Heaven, in- that they were not certain parts thereof, nor mutations made in the antient Stars, why doth he fet himfelf fo vigoroufly and earneftly dgainft the Comets, to banifti them by all ways from the Coele^ ftial Regions? Was it not enough that he could fay of them the fame which he f poke of the New fiars ? to wit> that in re- gard they were no certain parts of Heaven, nor mutations made in any of the Stars , they could no wife prejudice either Heaven, or the Doftrirte of AfiftotU > Secondly, I am not very wdl fatis- ficd of his meaning when he faith that the alterations that fiiould be granted to be made in the 5 tars , would be deftruftive to the prerogative of Heaven h namely , its incorruptibility, d^c. and this 5 becaufe the Stars are Coeleftial fubftances , as is manifeft by the confent of every one*, and yet is nothing troubled that •Excra Stellas. the fame altera tioi\s fliould be made * without the Stars in the reft of the Coeleftial expanfion. Doth he think that Heaven is no Coeleftial fubftanc^> I, for my part, did believe that the Stars were called Coeleftial bodies , by reafon that they were in Hea- ven? or fcJt that they were made of the fubftance of Heaven ; and yet I thought that Heaven was more Coeleftial than they, jn like fort , as nothing can be faid to be more Terreftrial, or more fiery than the Earth or Fire themfclves. And again, in that he ne- ver made any mention of the Solar fpots , which have been evi- dently demonftrated to be produced , and diffolved , and to be neer the Sun , and to turn either with, or about the fame , I have reafon to think that this Author probably did write more for others pleafure, than for his own fatisfadion h and this I affirm , foraf- much as lie having ftewn himfelf to be skilful in the Mathcma- ticks , it is impoffible but that he fhould have been convinced by Demanftration^ , that thofe fubftances are of neceffity contigu- ous with the body of the Sun , and are fo great generations and corruptions , that none comparable to them, ever happen in the 5^ith : And if fuch, fomany, and fo frequent be made in the very Globe of the Sun , which may with reafon be held one of the nobleft parts of Heaven , what fliould make us think that others may not happen in the other Orbs ? CenerAbiiny arJ Sagr. I cannot without great admiration , nay more, deni- ""^Zur^rfeai'^ ^^^^^ undcrftandiiig, hear it to be attributed to natural bodies, /« the Worlds ho' for a great honour and perfeftion that they are impaflible , im- t%^^LttuT' inalterable, ^c. And on the contrary , to bear it to

Impacible. bc

I A L O G U E I.

eaven.

eni-

iies.

mirablc

be eftcemed a great iinperfeaion to be alterable, gencrable, mu- . it is my opinion that the Earth is very noble and ad- by rcafon of fo many and fo different alterations, mu- rations, generations , which are inceffantly made therein and if without being fabjeft to any alteration , it had been all one vaft heap of fand , or a maffe of Jafp^r , or that in the time ox the Deluge , the waters freezing which covered it, it had t^ontinuedan immenfe Globe of Chriftal, wherein notbitig had ever grown , altered , or changed , I fliould have efteemed it a lump of no benefit to the World, full of idlencffe , and in a word fuperfluous , and as if it had* never been in nature and ihQuld make the fame difference in it, as between a living and dead creature : The hke Hay of the Moof^ jHpitcr, and the other Globes of the World. But the more I' dive into the con- fideration of the vanity of popular difcourfes-,: the more empty and fimple I find them. And what greater folly can there be imagined, than to call Jems, Silver and Gold pretious s and Earth aiiddirt vile> Fordo not thefe perfons con^der , that if there would be as great a fca-^^r Eartl» , a« jewels and

pretious metals. «=»^re would be no Prince, but would gladly give a heap o£ Diamonds and Rubies , and many Wedges of Gold to purchafe onely fo much Earth arffliould fuffice to plant a Geffe- mmein a little pot, or tafet theueirt ^ Qhina Orange^ that he m#gKt fee it fproHty grow up , and bring forth fo goodly leaves , fo odi- nferous flowers , and fo delicate fruit ? It is therefore fcarcity and plenty that make things efteemed and cohtemoed by the vulgar j who will fay that fame is a moft beautiful Diamond , for that it ^lembleth a clcer water , and yet will not part with it for ten fun of water: Thefc men that fo extol incorruptibility, inalte- rability, &*c. fpeak thus 1 believe out of the great defire they have to live long, and for fear of death ; not confidering, that it men had been immortal , they fliould have had nothing to do w the World. Thefe deferve to meet with a Mednfas head , that would transform them into Statues o( Dintond and JaJ}>er, that fo they might become more perfeft than they are.

S A L V. And it may be fuch a Metamorphafis would not be al- together unprofitable to them j for I am of opinion that it is bet- ter not to difcourfe at all , than to argue erronioufly-

S iM p L. There is not the leaft queftion to be made , but that Earth is much more perfefl:, being as it is alterable, mutable, than if it had been a maffe of ftone 5 yea although it were ^ne entire Diamond, moft hard and impaflile. But look how much lele qualifications cnoble the Earth , they render the Heavenly odies again on the other fide fo much the more imperfeft , in Which, fuch conditions would be fuperfluous , in regard that the

Coele^

4$

Tie Earth vsry noble J bj reason of the many mutati- ons made therein*

The Strth Mfffro- fitable and f^ll of idlenejje^ tts altc rations taken awAj

The Earth mort noble than Gold and Jewels,

Scarcity and plen^ tj enhanfeand de^ y^fe the price of things,

^"corruptibility e» fleemedbythevtil- £ar out of their fear of doAth,

The difparagers of corruptibility dc ferveto be turned ***to Status's, .

The Cotlr.flial be- dies deftgned to ferve the Earthy need no more bt^t motion and lights

Images reproduced by courtesy of the Royal Library, Copenhagen.

2°K.B. 9,163

46

G. G A L I L ^ us, his Syfieme.

Gttlefiial bodies , namely, the S'un, Moon, and the other Stars, which arc ordained for no other ufe but to ferve the Earth, need no other qualities for attaining of that end, fave onely thofe of light and motion. , , , , i

S AGR. How ? Will you affirm that nature hath produced and defigned fo many vaft perfefl and noble Coeleftial bodies , impaf- fiblc, immortal, and divine , to no other ufe but to ferve the paf- fible, frail, and mortal Earth > to ferve that which you call the dro£fe of the World , and fink of all uncleanneffe ? To what purpofe were the Gocleftial bodies made immortal, &c. to ferve a frail, &*c. Take away this fiibfervicncy to the Earth , and the in- numerable multitude of Coeleftial bodies become wholly unufe- CtUnui bodies ^ fuperfluous , fincc they neither have nor can have any TaLZc mutual operation betwixt themfelves i becaufe they are all unal- tion Hfon each o- tcrable, immutable, impaffible : For if , for Example, the Moon be impaflible , what influence can the Sun or any other Star have upon her ? it would doubtleffc have far leffe effeft upon her, than that of one who would with his looks or imagination , lignific a piece of Gold. Moreover , it feemeth to me, that whilft the Coc- kftial bodies concarre to the generation and alteration of the Earth, they themfelves are alfo of neceffity alterable ^ for other- wife I cannot underftand how the application of the Sun or Moon t0 the Earth , to efFea produaion , fliould be any other than to lay a marble Statue by a Womans fide , and from that con)unaion to expeft ckildren.

Afiiit SiMPL. Corruptibility, alteration, mutation, C^f. are not in

^Iminthe^hoic ^holc Tcrrcftrial Globe, which as to its whole^ is no lefTe eter- '^'''itfmfltit^^ Moon, but it is generabic and corruptible as ro

p^r^r its external parts j but yet it is alfo true that likewife in them ge-

neration and corruption are perpetual , and as fuch require the heavenly eternal operations , and therefore It is neceffary that the Coeleftial bodies be eternal

S AGR- All this is right j but if the corruptibility of the fuper- ficial parts of the Earth be nowife prejudicial to the eternity of its whole Globe , yea, if their being generabic, corruptible, alter- able, &*c. gain them great ornament and perfeaion j why can- CctUM hiies not, and ought not you to admit alteration, generation, &c. like- dterabie in their ^. ^j^^ extcmal parts of the Gocleftial Globes , adding to cm-tv^rd f^ts. ^^^^ ornament , without taking from them perfedion , or berea- ving them of aaion h yea rather encreafing their effeas , by grant- ing not onely that they all operate on the Earth, but that they mu- tually operate upon each other , and the Eaith alfo upon them all ?

S I M P L. This cannot be , becaufe the generations, mutations, ^c. which we fhould fuppofe v. g. in the Moon , would be vain and ufelelTe , & natura nihilfrnjira facit. S a G

Images reproduced by courtesy of the Royal Library, Copenhagen.

2°K.B. 9,163

D

lALOGUF. 1.

rs, htcd feof

rand

(ipaf- : paf- kthe

F

Qufe- tany

ive an lific a

Khe

Dther* Moon to lay

lot in tatcr- Ks to

ige-

r the ' that

Ipcr-

ity of

Sage. And why fliould they be vain and ufeleffe ? S I M p L. Becaufe we cleerly fee , and feel with our hands, tha

47

♦ o I M P L. eecaule we cleerly iee , and feel with our hands, that rhc^,H,ra,i», & all generations, corruptions, ^r. made in the Earth , are all ei- ther mediately or imniediately dire&d to the ufe, convenience, and benefit of man ; for the ufe of man are horfes brought forth, 'f tor the feedmg of horfes, the Earth produceth graffe, and the Clouds water it i for the ufe and nourifliment of man, herbs, corn, truirs, beafts, birds, fiflies, are brought forth i and in fum , if wc fliould one by one dilligently examine and refolve all thefc thmgs , wc flvjuld find the end to which they are all direfted, to be tne ncceQity, ufe, convenience, and delight of man. Now of what uie could the generations which we fuppofe to be made in the Moon or other Planets, ever be to mankind? unlcffe you fliouId lay that there werealfo men in the Moon , that might enjoy the benefit thereof ; a conceit either fabulous or impious.

ted ^-T' J ""^^ °' ' ^^^^ gen^"- ^'"^

u eitner herbs, or plants, or animals, like to ours, or that there »/

arc rams, winds, or thunders thcr<.. as about the Earth, I nci- f'^'' ther know, nor believ. 'nuch lefle , that u isthabited by

men : but yet i underftand not , becaufe there are not genera- ted things like to ours , that therefore it neceffarily followcth that no alteration u wrought therein, or that there may not be

«n.lv Tff^' ''''' "''^"S^' g^n"«^> anddiOblve, which are not onejyuitterentiromours, but excecdinely beyond our imagina- ^f^"""-""- t.on , and in a word not to be thought of by us. And iff as 1 ''"l.ru^"'" am certain, that one born and brought up inafpatious Forreft, ainongft beafts and birds , and that hath no knowledg at all of the

to DC in Na urc , difterent from the Eatth , full of living crea- .f,hc BU- mcs, which without legs or wings fwiftly move, and not upon 3 °^ thefurfaceouely, as beafts do upon the Earth, but in the very "tj;^'

owcls thereof; and not onely move , butalfo ftay themfelves and ceafe to move at their plealure , which birds cannot do in the a«r, and that moreover men live therein, and build Palaces and Vvities , and have fo great convenience in travailing , that without the kali trouble , they can go with their Family, Houfe, and no-le Cities , to places far remote , like as I fay, I am certain, a pcrfon, though of never fo piercing an imagination , could never fancy toJiimfelf Fiflies, the Ocean, Ship, Fleets, Arma- theVt ' '^^'^^ eafily, may it happn , that in

itanc " ' ''y great a fpace , and of a fub-

ters '^^ y^fy different from the Earth , there may be mat-

all o • not only wide off, but altogether beyond

./"^'"Jg^nations, as being fuch as have no refemblance to s, and therefoi e wholly inexcogitable,in regard, that what we

ima-

Images reproduced by courtesy of the Royal Library, Copenhagen.

2°K.B. 9,163

4S

rent from oftrs,

G. GhLiLMUSyhis Syfleme.

imagine to our felves , muft neceffarily be cither a thing already feen, or a compofition of things, or parts of things feen at ano^ ther time h for fuch are the SphinxeSy Sirenes^ Chim^eraSy Cen- tnursy Sec. ^

S ALV- I have very often let my fancy ruminate upon thefe fpe- culations , and in the end , have thought that 1 had found fome things that neither are nor can be in the Moon ^ but yet I have not found therein any of thofe which I believe are , and may be there , fave onely in a very general acceptation , namelyjthings that adorn it by operating, moving and living ^ and perhaps in a way There way he ffih' Very different from ours , beholding and admiring the greatnefs and fiances in the b^auty of the World , and of its Maker and Ruler, and with continual Encomiums finging his prayfes and in fumme (which is that which 1 intend) doing what facred Writers fo frequently af- firm , to wit , all the creatures making it their perpetual imploy- ment to laud God.

Sa.gr. Thefe are the things , which (peaking in general terms, may be there , but I would gladly hear you inftance in fuch as you believe neither are nor can be there j which perchance may be more particularly named.

Salv- Take notice Srf^r<?^/;^ that this will be the third time that we have unawares by running from one thing to another , loft our principal fubjea^ and if we continue thefe digreffions , it will be long ere we come tp a.conclufion of our difcourfe ^ there- fore 1 ftiould judg it better to riemit this , as alfo fuch other points, to be decided on a particular occafion.

S /V G R. Since we are now got into the Moon , if you pleafe, let us difpatch fuch things as concern her , thatfo we be not forced to fuch another tedious journey.

S ALV. It fhallbe as you would have it. And to begin with things more general , 1 believe th'at the Lunar Globe is far diffe- rent from the Terreftrial, though in fome things they agree. I will recount fitft their rqfemblances , and next their differences. The The Firft Moon is manifeftly like to the Earth in figure^ which undoubtedly 'XtJE^f^: is fpherical , as may be neceflarily concluded from the afpeft of its y„hich u that of (mi'sLcc f which ispetfeftly Orbicular, and the manner of its re- fnl'/"^^^^^^^ the Sun, from which , ifitsfurface were'flat,

nominated bj it would come tobe m in one and the lame time illuminated , and the Snn, likewifeagain in aricitlier inftant of time obfcured ^ and not thofe partsfirft, which are fituate towards the Sun, and the reft fuccef- lively ,i fo that in its oppofition , and not till then , its whole apparent, circumference is enUghtncd ; which would happen quite contrary > if thevifible fiirface were concaves namely, the illu- rhe Second con- ^nation would begin from the parts oppofite or averfe to the Sun, formitj is the Secondly flic is as the Earth , in her felf bbfcure and opacous , by Moons being opA' ^j^j^j^ opacity it IS enabled to teceivej and reflet the light of the

€oHs at the EArth, ^ o .

oun 3

efpe- Jbme

r'

amay things ay and ith lich is tly af- aploy-

le, let reed to

with r diffe- I will h The itedly a of its f its re- ^re'flat, d 5 and t thofe Ikccef* Fwhole fk quite the ilUi- :heSun. >us, by of the Sun 3

Thirdly^ The mat- tcr of the C^foon u

Eariht

Dialogue I. Sua j winch were it not fo, it could not do. Thirdly, 1 hold its matter to be molt denib and folid as the Earth is , which I clearly ^ argue from the unevenncls.of its fiiperficies in moll: places, by means ^'-^y^' oi the many ^dainencies and cavities ditcovered therein by help q^"'"'"^'^' the lelej cope : of which eminencies there are many all over it , di- rcfily rcfcmbliiig our moll (harp and craggy mountains, of which you (hall there perceive fomc extend and run in ledges of an hun- dred miles: long ^ ochers are contrafled lato rounder forms j and thereare alio jnany craggy, folitary, flecp and cli(fy rocks. But that vyhich there are frequenteft appearances, are certain Banks (1 uic thi^^'Oid, becaiife 1 cannot thing of another that better ex- pi;eileth th^m^- pretty high raifed, which environ and inclofe fields ok feveral.bigneires, and form . fundry figures, but for the moft pare cneular ^jpany of which have in the'midft a mount raifed pretty high, an4 iomeifew .are repleniQied with a matter fomewhat ob- icure, to wit, like to the great fpots difccrned by the bare eye, and thcle are of the greateft magnitude the number moreover of thofe tliat arc lefler ^nd lelTer is very great, and yet almoft all cirailar. r ourthly, like: as the furface of i« ^liftinguiHied into two ^^^'"'^^Z »

principal parts, navn->rV "^^^ ^^^^ Tcrreftrial and Aquatick .: fa ^f,"^"^ U'^IZ the Lunar lurface we diicern a great diftinftion of fome great fields "^'f^^'"' T^rts %l more refplendant, and fome lefs : whole afpeft makes me believe '{''''^ ''"^ '^f'''' that that of the Earth would feem very like it, beheld by zny on^^^L^ guf7Z ixpm the Moon, or any other the like diftance, to be illuminated rCZ^f^^l^ . by the Sun : and the furface of the fea would appear more ob- ^/^C^^/.t icure, and that ofthe Earth more bright. Fifthly, like as we from ^/'^^"/^"'r''^" the Earth behold the Moon, one while all illuminated, another fet^ ''^^ vyinle halti lometimes more, fometimes lefs ^ fometimes horned iometimes wholly mvifibly^ namely, when its juft under- the Sun t£t]:LZ Deams io that the parts which look towards tne Earth are dark : ^H^^/ thcM,on, Thus in every refpeft, one ftanding in the Moon would fee the r"'^"''*'^'?'* Illumination of the Earths furface by the Sun, with the fame periods to an hair , and under the fame changes of fieuFes. Sixtly, & &

S agr. Stay a little, Sahiatm-, That the illumination of the Earth,as to the feveral figures, would reprefent it felf to a perfon placed in the Moon, like in all things to that which we difcover in the Moon, I underftand very well, but yet I cannot conceive how wl ^ ^^^^^^ done in the fame period ^ feeing that that

^^hich the Suns illumination doth in the Lunar iuperhcies in a "^^nth, it doth in the Tcrreftrial in twenty four hours. 1 true, the cfFeft of the Sun about the illuminating

cic two bodies, and replenifiiing with its fplendor their whole jl' • ' difpatch'din the Earth in a Natural day, and in the ioon in a Month ; but the variation of the figures in which the

^ illumi-

Images reproduced by courtesy of the Royal Library, Copenhagen.

2°K.B. 9,163

G. G A L 1 L ^ 11 s, his Syjlcme.

illuminated parts of the Tcrreftrial fuperficies appear beheld from the Moon, depends not on this alone, but on the divers alpcds which the Moon is ftill changing with the Sun fo that, if for in- ftance, the Moon punftually followed the motion of the Sun, and flood,' for example , always in a direft line between it and the Earth, in that afpeft which we call Conjunfiion, it looking always to the fame Hemifphere of the Earth which the Sun looks' unto, flie would behold the fame all light : as on the contrary, if it Ihould always ftay in Oppofition to the Sun , it would never behold the Earth of which the dark part would be continually turn'd towards the Moon, and therefore invifible. But when the Moon is in Quadrature of the 5un, that half of the Terreftrial Hemifphere ex- pofed to the fight of the Moon which is towards the Sun, is lumi- nous i and the other towards the contrary is obfcure : and there- fore the illuminated part of the Earth would reprefent it felf to the Moon in a femi-circular figure.

SaGR. I clearly perceive all this, and under ftand very well, that the Moon departing from its Oppofition to the Sun, where it faw no part of the illumination of the Terreftrial fuperficies, and approaching day by day nearer the Sun , (he begins by little and little to difcover fome part of the iace of the illuminated Earth and that which appeareth of it Oiall refemblc a thin fickle, in regard the figure of the Earth is round : and the Moon thus acquiring by its motion day by day greater proximity to the . Sun, fucceffively difcovers more and more of the Terreftrial Hemifphere enlightned, fo that at the Quadrature there is juft half of it vifible, . inlbmuch that we may fee the other part of her : continuing next to proceed towards the ConjunSion, it fucceffively difcovers more and more of its furface to be illuminated, and in fine, at the time of Gonjun- aion fceth the whole Hemifphere enlightned. And in fiiort, I very well conceive, that what befalls the Inhabitants of the Earth, in beholding the changes of the Moon , would happen to him that from the Moon fliould obferve the Earth h but in a contrary order, namely? that when the Moon is to us at her full, and in Oppofition to the Sun, then the Earth would be in Conjunftion with the Sun,, and wholly obfcure and invifible i on the contrary, that pofition which is to us a Conjunftion of the Moon with the Sun, and for that caufe a Moon filent and unfecn, would be there an Oppofition ofthe Earth to the Sun, and, to fofpeak, Fnll Earth, to wit, all enlightned. And laftly, look what part of the Lunar furface ap- pears to us from time to time illuminated, fo much of the Earth in the fame time fhall you behold from the Moon to be obfcured : and look how much ofthe Moon is to us deprived of light, io much of the Earth is to the Moon illuminated. In one thing yet thcfe mutual operations in my judgment feem to differ , and it is, that it

being

^ well? vhcre it ^ and Ik and

HEarth a regard Mng by Rffively ightned, ilomuch proceed nd more Gonjun- fliort, I " Earth, him that ry order, )pofition :he Sun, pofition and for >polition ) wit, all •face ap- te Earth ^fcured : To much ret thefe

that it

D I A L O G U E I. 5^

being fuppofed^and not granted, that fome one being placed in the Moontoobiervc the Earth, he would every day fee the whole Terreftrial fupcrficies, by means of the Moons going about the Earth in twenty four or twenty five hours but we never fee but half of the Moon, fince it revolves not in it felf, as it muft do to be feen in every part of it.

S alv. So that this, bcfals not contrarily, namely, that her re- volving in her felf, is the caufe that we fee not the other half of her, for fo it would be neceffary it fliould be, if ftie had the Epicy- cle. But what other difference have you behind, to exchange for this which you have named ?

S A G R. Let me fee i Well for the prefent I cannot think of any other.

Salv. And what if the Earth (^as you have well noted) r^^j^^^^ no more than half the Moon, whereas from the Moon one may iee ti^! cMoo»"& tL all the Earth-, and on the contrary ,all the Earth feeth the Moon,and half o»eij of the but onely half of it feeth the Earth? For the inhabitants,to fo fpeak, ^^^^/'''^ of the fuperior Hemifphere of the Moon, which is to us invilible, are deprived of the fic^ht of *wiear*k and there haply are the AntiSihoHes, Bt.- ^^^^ ^ remember a particular accident, newly obferved by our Academian^ in the Moon, from whch are gathered prem the Sarth two necelTary confequences , one is, that we fee fomewhat more fee more than than half of the Moon^ and the other is, that the motion o{ th^^^l^^f' ^"""^^ Moon hath exa& concentricity with the Earth ; and thus he finds the Phcenomenon and obfervation. When the Moon hath a cor- refpondence and natural fympathy with the Earth, towards which it hath its afpeft in fuch a determinate part, it is neceffary that the right line which conjoyns their centers , do paffe ever by the fame point of the Moons fuperficies, fo that, who fo fliall from the cen- ter of the Earth behold the fame , fliall alwayes fee the fame DifcHS or Face of the Moon pundually determined by one and the fame circumference i But if a man be placed upon the Terre- ftrial furface, the ray which from his eye palfeth to the centre of the Lunar Globe, will not pafs by the fame point of its fuperficies , by which the line paffeth that is drawn from the centre of the Earth to that of the Is4oon, fave onely when it is vertical to him : but the Moon being placed in the Eaft, or in the Weft, the point of incidence of the vifual ray, is higher than that of the line which conjoyns the centres j and therefore the obfcrver may difccrn fome part of the Lunar Hemifphere towards the upper circumfe^ r^nce, and alike part of the other is invifible : they arc difcerna- bleandundifcernablejin refpeft of the Hemifphete beheld from the true centre of the Earth : and becaufe the part of the Moons circumference, which is fuperiour in its rifing, is ncthertnoft in its fetting j therefore the difference of the faid fuperiour and infcri-*

G 2 our

G. G A L I L u his Syjieme.

our parts muft needs be very obfervable j certain fpots and other notable things inthofc parts, being one while difcernablc , and another while not. A like variation may alfo be obferved towards the North and South extremities of the fame Dijcus (or Surface) according as the Moons pofition is in one or the other Seftion of its Dragons For, if it be North, fomc of its parts towards the North are hid , and fomc of thofe parts towards the South are difcpyered, and fo on the contrary. Now that thefe eonfequen- Two ipjts in thg cesare really true 5. is verified by the Tele f cope •> for there be in ^Te^ct^zt''^^^^^ one of which, when the Moon

{hi hath reff^a to is in tlie meridian , is fituate to the Northwclt , and the other is th, ''/^^^^ almoft diametrically oppofire unto it 5 and the firft of thefeisvi-

Earth tn her mo- t ^ i r i i t .

tio;j. fible even without the lelejcope ^ but the other is not. That to-

wards the Northweft is a reafonable great fpot of oval figure , fe- para ted from the other great ones theoppofite oncislefTe, and alfo fevered from the biggeft 5 and fituate in a very deer field j in both thgfe we may manifeftly difcern the forcfaid variations , and fee them one after another now neer the edge or limb of the Lunar Z)//67^ 5 and anon remote , with fo great difference that the dift^nce betwiKt the Northweft and the circumiference of the pifcmh more than twice; as great at one time, as at the other i and to the fecjond fpot (bepaufe it is neercr to the circuipfe- rence) fuch mutatiw importeth more , than twice fo much in the former- Hence its manifeft, that the Moon , as if it were drawn by % magnetick vertue , conftantly beholds the Terreftrial Globq with one and the f^me afpe£i:,; never deviating from the fame,

S ^Gil. Oil 1 when will there be an end put to the new ob- fervgtipAs aud difcOiveries of this admirable Inftrument ?

Sa l v- If this fuceced according to the progreife of other greAt invention?, it is to be hoped > that in prpccffe of time , onqmay arrive tq the fight pf things y to us at pjtcfent not to be imagined. Sixthly , The g^^ r/e turning tQ.Qur firft difcourfe , I fay for the fix^h rcfembl^nce ft^L'^i^'^^ ^hat as the Moon for agrea^ p^^ri

illuminate. of tim^.j fupplies tb^ \vani; pf the Si4ij> light , and mak^§,}ii nights: . by the refleaiop, .its own, reafonable clear ^ fp the Bmh , recpmpp^nce , affprd^thit wkn itftandsin moft ,^^4^ rfiflectif^ rayes^j j^yery rpleqr illumination , ar\4 fo

muchyin myopipioni> greater thw . that w^^^ cpmeth from hep to^ U5,. how much th^lupeffi^iespf thl E^rth is greater tha^t^h.^c

of.the ;Moo-n»:-.;.; : .-.Oj ^.-./.i-Jhiii'^V? :,/X^-"ri'

- S-^Gi^ Hold jthere j Sal<^i^tHS Wd theire, and permit me the pleafur^jS>f rielating tp you, bow at this firft hint I have penetrated the caufe of 2^1^ aQejdent , which I have a thoufand times thought fromfh! sluhm^ "P^"^ fcut cpuld n^vcr find out. You would fay, that the imper- to the Moon* feet light whickisfeen in the Moon 5 efpecially when it is horned, • - . comes

D

Other , and wards face) ion of fis the th. are quen- be in Moon ther is e is vi- p:to-

; , aad Id h in ) an<i of the e that of the other i :mi;ife- in the ^wn Pobe ►^T.

?w ob-

i^jnay gined.

plj^nce IF psirit the r^^the

\M fo

comes from the reflcfiion of the

I ALOG UE.

ri^co^.u V"'L^^"Tr""* ^"^ lig'jt of the Sun on thcSuperfi- aesof the Earth and Sea , and that light is more clear, by how

expoled to the Mno„ • ^"'^^^"^ ^'^'^ luminous part of the Earth,

&on 1 ^ " i 'llummated part of the Earth beheld ffotn

sTTv ' '"^T^"" °^ ''g^^ ""'^h the more potent.

Inaword .''''r^'""' ^"'^ ^ abouttofay.

andapSenfi t f ? ^ "-^^''^ ^^"'^ with perfons judicious fonveEd i f ' ^"'*^'»\r^^hertome, for that whilcft pthers ny times Sei °"'u^ Axiomatical truths , I have ma-

S V. b^ain Tucha.duou, Paradoxes, that

^x S hllZtr AT'' '■^^^^'■^^ "''^i'^h you at the ve- ^i!^^^::!^'''^'^^''''^'^^^ yetcx>ul/lnever beat * S-I M P i. If you mcanJ-r-y*»"r "oc beingabw t*ip«.fwade .1^^

to K , that you-^« not make them underftand the fameT T m«ch.wo«dcrthereat , and aai very iioiifident t^jat if thev d.d Bot underftand u % your demonftriion <your way of ex^rTflJo^

apprehended rt upon the CKplication any Other man - but if

^T'l^-'^^'^T^^^ ' fo'ast^mrt'hemU' Sf "°"^^^"f^'/" **^his5 for i confefle my

the XTJ^V V for there:a*e in this, andf^me^

wteXKS ;^«^^u«.es, or refemblances, taaby difficulties, r ,^ ' ""^^^ 5«» *ive gone tWgH thcfll

whe^' J i- '*' 1 fin<J o«fcaoy truth , in the' acqiiift

mit^i^^'""'^ ihtclligentperfons (fuch as your felf)V tJiat -wiuch.remains Fo.S? ™1 ^^^^^^y bnef ,n d,fpatchi«g prQc^fefponf^'^; /°;*/^venth coBfor^^^

Moon • J^l c . , > a^favours ; whereby the E^'h

inte^^ heighiiof its illuminadon , by the ^'"'"•'i^J cciiff,.

QbiSwh.K ^'T" ^"'^ 'J*^ Sun, and with its ftadow

able to and although the revenge be not anfwer-

that for i T''^;' that the Moon often continueth, and fliadow \[f^^^°"able long time, wholly immcrfed in the Earths

P'ed by the Moon j yet, nevertheleffe , having ripect to the

fmal-

Images reproduced by courtesy of the Royal Library, Copenhagen.

2°K.B. 9,163

54

G. GALiLiEUs,fc<x e 1 nu^f the bodv of this, in comparifon to the magnitude Ke ^ther it -not be denied bu't that the and as ic tre J nrkthis, is very great. Thus much for the.r con- ruTtiesorrefemblances. It fhould next follow that we difcourfe fouching their difparity ; but bccaufe SmfUan. will favour U8 his objections againft the former its neceffary that we hear and examine them , before we proceed any farther.

S AcrAnd the rather, becaufe It is to be fuppofed that Si JlUiHs will not any wayes oppofe the difparines , and mcon- gluities betwixt the Earth and Moon , fmcc that he accounts their fubftances extremely different. • j • .

S I M P r . Amongft the refemblances by you recited , in the pa- ralle vou make betwixt the Earth and Moon , I find that 1 can admit none confidently fave onely the firft, and two others i I grant the firft, namely, the fphcrical figured howbeit, even in This there is fome kind of difference , for that 1 hold that oi the Moon to be very fmooth and even, as a looking-glafle , where- as, we find and feel this of the Earth to be extraordinary montu- ous and rugged ; but this belonging to the inequality of fuperfi- de it (hall be anon confidered, ,n another of thofc Refemblan- Sy iou alledged ; I fhall therefore referve what 1 have to fay Sereof , till 1 come to the confiderauon of that. Of what you incrcui, ti Moonfcemeth, as you fay m your fecond

i f mSce, opacousand obfcure in its fclf , like the Earth i I dmli not any more than the firft attribute of opacity , of which the Eclipfes of the Sun affurcme. For were the Moon tranfpa- rent the air in the total obfcuration of the Sun , would not be- come' fo duskifh, as at fuch a time it is, but by means of the tranfparcncy of the body of the Moon, arefraaed light would palTe through it, as we fee it doth through the tWckeft clouds. But is to the obfcurity , 1 believe not that the Moon is wholly depri- ved of light , as the Earth i nay, that clarity which is fcen m the remainder of it. Difcns, over and above the fmall crefccnt en- liehtened by the Sun , 1 repute to be its proper arid natural hght, , J f ■ andnntarefieaionof the Earth, which 1 cftcem unable , by rA«::r:^«afoTof itsafperity (craggineffe) and obfcurity , to reflea the filmed « h it, \ " . c n. In the third Parallel I alTent unto you in one "^;t4L.. SI". anddHTcntin -other : I agree in judgingthe body of the „ rcfi^a th, SHm ^^^^^ folid and hard , like the Earth , yea much more ,

'ri?M/-« for if from Ariftotk we receive that the Heavens are impenet«ble, ,y woven, imp,- and the Stars the moft d^nfe pa^^of H^^^^" ' "^^^ neceffanly

t:fJM follow, that they are ffloft folid and moft impenetrable.

„^ MoCc ^^^^^ ^^J^ ^^^^^j^^^ ^^^^^^^ ^ j^^ ^^^^^^^ ^^^^^ f

to make Pallaces of, if we could procure a fubftance fo hard and fo tranfparent

nitudc

1 as it T con- Tcourfe rour \i9 rc hear

tthat icon- their

the pa- Klcan Irs^ I

even in ^£ the lere- montu- ^pcrfi* Pblan-

2 to fay hat you : fccond arth ) t >f which tranfpa- not be- sof the t would ids. But y depri- in in the :cnt cn- 5il light, le , by Ac& the

rm one of the :h more? ictrable? ^ffarily

)vd us for and [o

ALV

D I A L O G U E. I.

S ^Lv. Rather how improper, for being by its tranfparencc.

wholly invifible, a man would not be able without ftumblingat the threfliolds, and breaking his head againft the Walls, to pais from room to room. *

S \ G R. This danger would not befall him, if it be true, as fome 7hfM4.cfof PtripatttiL^f fay, that it is intangible : and if one cannot t^taK^t- touch it, much Icfs can it hurt him.

S A L V. This would not ferve the turn, for though tlie matter of the Heavens cannot be touchc, as wanting tangible qualities : yet may it ealily touch the elementary bodies . and to offend m it is as tufficient that it ftrikc us, nay worfe, than if we fliould firikc it. But let us leave thcfe Fallacesy or, to fay better, thefe in the air, and not interrupt S I M P L. The queftion which y oia have fo cafually ftarted, is one of the moft difliculty that isdifputed in Philofophy and I have on that fubjeft moft excellent conceits of a very learned Doftor of Fddoua^ but it is not now time to enter upon them. Therefore returning to our purpofc, I fay that the Moon, in my opinion, is much more folid than th^ E-^cn, t>nt do «ot inf^r the lame, as you do, from the cra*gginels and montuofity of its fuperficies ; but The [nper fides of rather from the contrary, namely, from its aptitude to receive (fas more we fee it experimented in the harideft ftones) a polifli and luftre ^u%J^l''u{i exceeding that of the fmootheft glafs , for fuch neceffarily • muft ' its fuperficies be, to render it apt to makefo lively reflection of the Suns rays. And foj: thofe appearances which you mentioa. of Mountains, Cliffs, Hills, Valleys, &c. they are all illufions ': and I have been prefent at certain publick difputes, where I have ueard it ftrongly maintained againft thcfe introducers of novelties, that fuch appearances proceed from nothing elfc> but from thcun- MoZ'^lrflihlt equal diftribution of the opacous and perfpicuous parts, of which ofTf oplcaJ^'Jul the Moon is inwardly and outwardly compofed : as we fee itf^^^*^'*^'*^?^^^'' often fall out in chrjftal, amber> and many other precious ftones ot perfea luftre v in which by reafon of the opacity of fome parts, and the tranfparency of others, there doth appear fcveral conca- vities and prominencies. In the fourth refemblance, I gr^nt, that the (upcrficies of Terreftrial Globe beheld from afar, would make tvvo ditferent appearances, namely, one more clear, the other more ^ dark ^ but 1 believe that fuchdiveifity would fuccccd quite con- trary to what you fay *, that is, I hold that the furface of the wa- ^er would appear lucid, becaufe that it is fmooth and tranfparent i ^^d that of the Earth would appear obfcure, by reafon of its o- F^»ty and fcabrofity, ill accommodated for reflefting the light of ^ijn. Concerning the fifth conn^parifon, I grant it wholly, and am able, cafe the Earth did (hinc as the Moon, to (how the iametoanyone that fliould from thence above behold it, reprc-

fented

5^

fcntcd by figures anfwcrablc to thole which we Ice in the Moon : I comprehend alio, how the period of its illumination and varia- tion of figiue, would be monthly , albeit the Sun revolves round ^ about it in twenty four hours : and laftly, I do not fcruple to

admit, that the half onely of the Moon fceth all the Earth, and that ail the Earth feeth but onely half of the Moon. For what remains, I repute it moft falfe, that the Moon can receive light from the Earth, which is moft obicure, opacous, and utterly un- apt to reileft the Suns light, as the Moon doth refleft it to us : and as I have faid, 1 hold that that light which we fee in the remain- der of the Moons face ^the fplendid crefcents lubduftedj) by the illumination, is the proper and natural light of the Moon, and no eafie matter would induce me to believe otherwife. The feventh, touching the mutual Eclipfes, may be alfo admitted , howbeit that is wont to be called the eclipfe of the Sun, which you are pleafed to phrafe the eclipfe of the Earth. And this is what / have at this time to fay in oppofition to your feven congruities or refemblances, to which objedions, if you are minded to make any reply, 1 fliall willingly hear you.

Sal V. If I have well apprehended what you have anfwered, it feems to me, that there ftill remains in controverfie between uSjCer- tain conditions, which I made common betwixt the Moon & Earth, and they are thefe^You efteem the Moon to be fmooth and poliflit, as a Looking- glafs, and as fuch, able to reflcft the Suns light and contrarily,the Earth, byreafon of itsmoijtuofity, unable to make fuchrefleftion: You yield the Moon to be folid and hard, and that you argue from its being fmooth and polite, and not from its being montuous j and for its appearing montuous, you aflign as the caufe, that it.confifts of parts more and lefs opacous and perfpi- cuous. And laftly, you efteem that fecondary light, to be proper to the Moon, and not refleded from the Earth ^ howbeit you feem not to deny the fea , as being of a fmooth furface , feme kindof refleftion. As to the convincing you of that error, that the icflection of the Moon is made, as it were, like that of a Lookine-glafsj I have fmall hope, whilft I fee, that what hath *JlSaggiatcre,Sc ^^^^ thc'^ Saggi at or and in the Solar Letters of our Com-

tJ^rrt.z^!^'o^ profited nothing in your judgment, if haply

CalfUMs. you have attentively read what he hath there written on this iub- )cct.

SiMPL. I have pcrufed the fame fo fuperficially, according to the fmall time of leafure allowed me from more fohd ftudies j therefore, if you think you can, either by repeating fome of thofe reafons, or by alledging others, refolve me thefe doubts, I will hearken to them attentively.

S AJ-V. I will tell you what comes into my mind upon the

inftant,

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2°K.B. 9,163

i'> It asjcer- Earth) ►oliflit, 5 and make id that I being as the perfpi- proper It you fome ir, that |o f a fhath r Com- haply |fub-

Eng to tudies j f thofe

Dialogue L' '^j^.' ,

inftaat , and its polliblc it may be a commixtion of my Own d)n- ceipts 3 and thofe which I have fometime read in the fore-faid Books , by which I well remember , that I was then perfectly Satisfied, although the conclufions, at firft fight feem^d unto me ftrange Paradoxes. Wc cncimvG Simplicius , whether to the ma- king a reflection of light, like that which we receive from the Moon , it be necelTary that the fuperficies from whence the refle- ction commeth , be fo fmooth and poHte, as the face of a Looking- Glaflb , or whether a fuperficies not fmooth or poliflit , but rough and uneven , be more apt for fuch a parpofe. Now fuppofing two reflections fliould come unto us , one more bright , the other * I fuperficies oppofite unto us , I demand of you,

which of the two fuperficies you think would reprefent it felf to Our fight , to be the cleareft , and which the obfcurcft.

Sim p t . I am very confident , that that fame , which moft for- cibly reflefied the light upon me , would flicw its felf in its afpeft the clearer, and the other darker. .

w!n ^^1^ ^^^^^""^ ^""^^ ' ^^^^^ ^^^'^^ ^^^"g^ y^"^^^ ^ P-^'^ ^

Wall, and let us go ou*i"^o the Court-yard. Com^ Sa^redus^''^^' t%at the Now hang the gi^fle yonder, againft that fame Wall , on which ^"'"^ ff*rfdce it the Sun (hines , and now let us with-draw our felves into the fliade See yonder two fuperficies beaten by the Sun , namely, the Wall andtheGlaffe. Tell me now which appears cleareft unto you, that of the Wall or that of the Glaffe ? Why do you not anfwcr

SA GR Heave the reply to who made the quefti-

oinLinaof.?''"'^ own part, am perfwaded upon thi. fmall be- polX^urface"^'""'"' ' '""^ ^ ^^^^ -

S A L V. What fay you Simplicim , if you were to depaint that wall and that Glaffe fattened unto it, where would you ufc your darkeft colours, in defigning the Wall , or elfe in painting the Looking-C laffe. ^

Simp l. Much the darker in depainting the Glaffe. J>ALv Now if from the fuperficies, which reprefents it felf more clear there proceedeth a more powerful refleaion of light.

Simp I,. Very well, Sir, have you ever a better experiment ^nanthis? you have placed us where the Glaffe doth notrever- wiU you^^Vft ' along with me a little this way ; how,

Chile inaklh" ^^^^ ^'"""^ °^ ^flcaion, which the

SiMPl. 1 dofo. '*

H

SaGR'

Images reproduced by courtesy of the Royal Library, Copenhagen.

2°K.B. 9,163

G. G A L I L ^ us, hh Syfleme]

S \ G R Why look you, there it is upon the oppofite Wall, ^uft as big as the Glaire , and little leffe bright than if the Sun had direftly fhined upon it.

S I M p L. Come hither therefore , and fee from hence the fur- face of the Gla{fe , and tell me whether you think it more ob* fcure than that of the Wall.

S A G R- Look on it your felf 9 for 1 have no mind at this time, to dazle my eyes , and 1 know very well , without feeing it , that it there appears as fplendid and bright as the Sun it fclf , or little leiTe.

SiMPL. What fay you therefore, is the refleftionof aClafTe leffe powerful than that of a Wall ? 1 fee, that in this oppofite Wall , where the reflcciion of the other illuminated Wall comes', together with that of the Glaffe , this of the Glaffe is much clearer h and 1 fee likewife , that, from this place where I ftand, thc= gUffe it felf appears with much more luftre than the Wall.

S A T V. You have prevented me with your fubtlety ^ for I flood in need of this very obfervation to demonftrate what remains. You fee then the difference which happens betwixt thetworeflc* fiions made by the two fuperficies of the Wall and Glaffe, per'* cu ft in the felf-fame manner , by the rayes of the Sun h and you fee , bow the reflection which comes from the Wall , diffufeth it fclf towards all the parts oppofite to it, but that of the Glaffe gocth towards one part oncly , iK>t at all bigger than the Glaffe it felf: you fee likewife? how the fuperficies of the Wall, beheld from what part foeVer , alwayes fliews it felf of one and the fame cleerneffe , and every way , much clearer than that of the Glaffe, excepting only in that little plaice , on which the Glaffes reflection reverberates, for from thence indeed the Glaffe appears much more lucid than the Wall. By thcfe fo fcnfible , and palpable experi- ments, my thinks one may foon come to know , whether the reflection which the Moon fends upon us , proceed as f om a Glaffe ,