'Of Colours'

Of Colours.

1. The rays reflected from Leafe Gold are yellow but then transmitted are blew, as appears by holding a leafe of Gold twixt yoryour eye & a candle.

2. Lignum Nephriticum sliced & about a handfull infused in 23 or 4 pints of faire water for a night yethe liquor (looked on in a cleare violl) reflects blew rays & transmits yellow ones. And if yethe liquor being too much impregnated appeares (wnwhen looked through) of a darke red it may be diluted wthwith faire water till it appeare of a Golden Colour.

3 The flat peices of some kinds of Glase will exhibit yethe same Phænomena wthwith Lignum Nephritcum And these Phænomena of Gold & Lignum Nephriticum are represented by yethe Prisme in yethe 37th experiment as also in yethe 22dth & 24th Experiment.

4 But Generally bodys wchwhich appeare of any colour to yethe eye, appeare of yethe same colour in all positions; Nay Gold if it bee not soe very thin as to bee transparent appeares onely yellow & perhaps yethe yellow colour of Lignum Nephriticum would vanish if yethe tincture bee strong & yethe liquor of a greate thicknesse. And perhaps there are many coloured bodys wchwhich if made so thin as to bee transparent would appeare of one colour ~~to yethe~~ when looked upon & of another colour when looked through. Perhaps Motes in yethe Sun doe so for they appeare coloured. And

5 The tincture of Lignum Nephriticum may bee deprived of its blew colour wthwithout any alteration made in yethe yellow. by putting a little of any acid salt into it (as spirit of Salt of vinegar, of Lemon juice, oyle of Vitrioll, Aqua fortis &c). Sulphureous Salts (whither Vrinous (i.e. Volatile salts of Animal substances) as Spirit of hartshorne of Vrin; of blood, of Sal Armoniack; Or Lixiviate Vnctuous Alcalizate & fixed salts made by incineration as yethe Solution of Salt of potashes, of common wood ashes, of lime water, Oyle of Tartar &c) doe restore yethe blew colour wthwithout making any change in the yellow.

Of Colours.

Experiments wthwith yethe Prisme

On a black peice of paper I drew a line opq, whereof one halfe op was a good blew yethe other pq a good deepe red (chosen by Prob. of Colours). And looking on it through yethe Prisme adf, it appeared broken in two twixt yethe colours, as at rst, yethe blew parte rs being nearer yethe vertex ab of yethe Prisme ynthan yethe red parte st. Soe ytthat blew rays suffer a greater refraction ynthan red ones. Note I call those blew or red rays &c, wchwhich make yethe Phantome of such colours.

The same Experiment may bee tryed wthwith a thred of two colours held against yethe darke.

7 Taking a Prisme, (whose angle fbd was about 60dr into a darke roome into wchwhich yethe sun shone only at one little round hole k. ~~The colours~~ And laying it ~~yethe Prism~~ close to yethe hole k in such manner ytthat yethe rays, being equally refracted at (n & h) their going in & out of it, cast colours rstv on yethe opposite wall. The colours should have beene in a round circle were all yethe rays alike refracted, but their forme was oblong terminated at theire sides r & s wthwith streight lines; theire bredth rs being 2

\frac{1}{3}

inches, theire length to about 7 or eight inches, & yethe centers of yethe red & blew (q & p) being distant about 2

\frac{3}{4}

or 3 inches. The distance of yethe wall trsv from yethe Prisme being 260 inches

8 Setting yethe Prisme in yethe midst twixt yethe hole k & yethe opposite wall, in yethe same posture, & laying a boarde xy betwixt yethe hole k & yethe Prisme close to yethe Prisme, in wchwhich board there was a small hole as big as yethe hole k (viz:

\frac{1}{8}

of an inch in Diameter) so ytthat yethe rays passing through both those holes to yethe Prisme might all bee almost parallel (wanting lesse ynthan 7 minutes, whereas in yethe former experiment some rays were inclined 31min). Then was the length & breadth of yethe colours on yethe wall every way lesse ynthan before halfe yethe former by about 2 inches viz rs =

\frac{3}{8}

inch, tv = 2

\frac{3}{4}

inch inches. & pq = 1

\frac{1}{4}

inch Soe ytthat yethe Red & blew rays wchwhich were parallel before refraction may bee esteemed to be generally inclined one to another after refraction some more some lesse ynthan) 34min. And ytthat some of them are inclined more ynthan a degree, in this case. And therefore if theire sines of incidence (out of glasse into glasse aire) be of yethe same, theire sines of refraction will generally bee in yethe proportion of 285 to 286 & for yethe most extreamly red & blew rays, they will bee as 130 to 131 +, : ffor by experiment if their angle of incidence out of yethe glasse into yethe aire bee 30d. The angle refraction of yethe red rays being 48gr 35': yethe angle of refraction of yethe blew rays will bee 48gr, 52', generally but if yethe rays bee extreamly red & blew yethe angle of refraction of yethe blew rays may bee more ynthan 49gr, 5'. 9 In yethe 7th Experiment yethe colours appeared in this order. but in yethe 8th exper:experiment when yethe rays were more distinct & unmixed 10 Painting a good blew or red colour on a peice of paper neither of wchwhich was much more luminous ynthan yethe other (for carrying ymthem gadually into yethe darke, both grew faint alike almost & disappeared together) if yethe Prismaticall blew fell upon yethe colours thay both appeared perfectly blew but yethe red paint afforded much yethe fainter & darker blew, but if yethe Prismaticall red fell on yethe colours then both appeared perfectly ble red but yethe painted blew afforded much yethe fainter Red. The Prisme was ordered as in yethe 8th experiment. Note ytthat yethe purer yethe Blew Red is yethe lesse tis visible wthwith blew Red rays. Of Colours of colours 11 If yethe plate abcdsr bee painted wthwith any two colours & abcd bee yethe lighter colour, yethe partition edge of yethe Colours, cd will bee appeare through yethe prisme txy of a red colour, but if cres bee yethe lighter colour, their common edge cd 12 will through a prisme looke blew. 12 And this will happen though yethe colours differ not in species but only in degrees, as if acdb bee black & cdsr darkness or blacker ynthan abdc yethe edge dc will bee red & much more conspicuous ynthan yethe black, wchwhich is strange. 13 But if in a darke roome (as in ExperimntExperiment 10) yethe prismaticall blew or redd fall on a paper abdc yethe edges of yethe paper will not appeare otherwise coloured through another Prisme ynthan to yethe naked eye, viz: of yethe same colour wthwith yethe rest of yethe paper. [ffor yethe first Prisme perfectly seperats yethe blew & red rays whereas I beleive all yethe colours proper to bodys are a little mixed.] 14 Prismaticall colours appeare in yethe eye in a contrary order to ytthat in wchwhich they fall on yethe paper. 15 If a foursquare vessell abcd bee made wthwith two parallel sides of well pollished glasse AC BD, & bee filled wthwith water; And if yethe sunns rays doe passing into a darke roome through yethe hole k doe fall very obliquely on yethe glasse sides of yethe vessell & through yethe rays at their egresse shall paint colours on yethe paper EF on wchwhich they fall. [The blew & red colours rays being seperated by yethe first refraction.] 16 The colours are not made broader (as they would be were yethe prisme triangular) by removing yethe paper farther from yethe vessell. [becaus yethe blew & red rays become parallell againe after yethe second refraction] if the rays pass through two holes near or close to yethe vessell on either side yethe colours Of Colours. 17 The window k being opened ytthat yethe Sun or other terminated light might shine freely, If I limited yethe rays by an opace body held twixt yethe wall & yethe vessel yethe edge of yethe bodys shaddow would not appeare coloured. But if yethe said body were on ytthat side yethe vessel towards yethe sun its shaddow would be coloured on its edge 18. But in yethe Triangular Prisme whither yethe said body bee held on yethe one side or on yethe other the edges of its shaddow appeares coloured. 19. If you looke upon some uniformely luminous body (as on yethe cleare sky or a sheet of white paper &c) through a triangular prisme. & hold yethe said opace body on yethe farther side of yethe Prisme soe as to obscure one halfe parte of yethe said luminous body; the farther yethe said opace body is held from yethe Prisme, yethe more its edges will bee coloured; & yethe nearer, yethe lesse; untill yethe colours quite almost vanish when yethe said body becomes contiguous to is held close close to yethe Prisme. 20 But if instead of yethe triangular Prisme you use yethe said 4square vessell ABDC, held obliquely ytthat yethe rays may bee much refracted in passing through it to yethe eye when yethe opake body is placed as neare to yethe vessell as you can distinctly see it, yoryour eye being close to yethe vessell, yethe edges of yethe said body will appeare coloured wchwhich colours are diminished by removing yethe body farther from yethe vessell, & quite vanish when yethe distance of yethe said body is very greate. Thus yethe Sun, by reason of his distance, appeares not coloured on his edges wnwhen looked on through yethe said vessell, & yet in yethe 15th experiment hee trajects colours on a peice of paper. 21 The colours made by this vessel appeare imediatly to yethe eye in yethe same order in wchwhich they fall on paper but by yethe △ Prisme ytthat order is divers. Note, That yethe more yethe glasse sides of yethe vessell ABCD are distant, yethe better it is; ytthat distance should not bee lesse ynthan 6 or 8 inches to make yethe Phænomena conspicuous. Some of yethe Phænomena may bee tryed by tying two Prismes thus together: But yethe distance of theire sides is too little to exhibit ymthem Of Colours 22. If yethe sun S shine upon yethe Prism def, some of his rays being transmitted through yethe base ef will make colour on yethe wall cb at b, others will bee reflected colouring yethe wall to yethe wall at c making only a white wthwithout colours; Now if yethe Prisme bee soe inclined as that yethe rays ab bee refracted more & more obliquely, yethe blew colour will at last vanish from b; soe ytthat yethe red alone being refracted to b, yethe blew will bee reflected to c & make yethe white colour there to appeare a litttle blewish. But if yethe Prisme bee yet more inclined, yethe red colour at b will vanish too & being reflected to c will make yethe blewish colour turne white againe. 23. If in yethe open aire you looke at yethe Image of yethe Sky reflected from yethe bases of yethe Prism ef, holding yoryour eye O almost perpendicular to yethe basis you will see yethe one part of yethe sky ep (being as it were shaded wthwith a thin curtaine) to appeare darker ynthan yethe other qf. [ ffor all yethe rays wchwhich can come to yethe eye from qf, fall soe obliquely on yethe basis as to bee all reflected to yethe eye. Whereas those wchwhich fall soe can come to yethe eye from ep are so direct to yethe basis as to bee most of ymthem in front transmitted to g]: & yethe partition of those two parts of yethe Sky, pq, appeares blew; [ffor yethe inclinations of yethe rays , wchwhich can come to yethe eye from pq, are so inclined to yethe basis ytthat all yethe blew rays are reflected to yethe eye whilst most of yethe red rays are transmitted through to g as in ExperimntExperiment 22] 24 Tying two Prismes basis to basis def & bef together I so held ymthem in yethe sun beames transmitted through a hole into a darke roome, ytthat they Of Colours. falling pretty directly upon yethe base ef (in fig 1) were most of ymthem transmitted to B on yethe paper CB; though some of ymthem were reflected to C by yethe filme of aire ef betwixt yethe Prismes.But both C & D were white Then I inclined yethe Basis (ef) of yethe Prismes more & more to yethe rays untill B changed from white to Red, & yethe white at C became blewish; & inclining yethe Prisme a little more yethe Red at B vanished, & yethe blewish colour at C became white againe. As in yethe 22th Experiment. 25 If I held yethe said Prismes in yethe open air as in yethe 23d experiment, holding my eye at O (in yethe 2d fig) to see yethe reflected sky yethe Phænomena were yethe same as in ytthat 23d experiment; ep appearing darker ynthan qf, & pq being blew. But if I held my eye at N to see yethe sky through yethe base of yethe Prismes ef (or rather through yethe plate of aire betwixt those bases) there appeared yethe contrary Phænomena but much more plaine ep being very light, qf very darke, & pq very red. [The reason was given in yethe 23d experiment Note, That yethe 22th & 24th (& all such like experiments ytthat require ytthat yethe rays coming from a luminous body be all parallell wholly or almost parallell) would bee more conspicuous were yethe suns Diameter lesse, & therefore for such like experiments his rays may bee straitned through two small holes at a good distance assunder, as was done in yethe 8th Experiment. Also yethe 23th & 25t Experiment (& most other such like in wchwhich like immediatly the rays passe immediatly from yethe prisme to yethe eye) would bee more conspicuous were yethe Pupill lesse ynthan it is, And therefore it would bee convenient to looke through a small hole at yethe Prisme. 26 The colours in yethe portion pq appeared to yethe eye O in this order Of Colours. 27 The two Prismes being tyed together then in trying yethe 24th experiment, there appeared a white spot in yethe midst of yethe red colour B, & a darke spot in yethe blewish colour C. And after yethe base ef of yethe Prismes was more more inclined to yethe rays , so ytthat yethe red colour vanished & ytthat (by yethe laws of Refraction) noe light could penetrate yethe filme of aire ef, yet yethe white spot remained at B & yethe blew darke one in yethe midst of yethe light at C. 28 Holding my eye at O or N (in trying yethe 25t Exper:Experiment) very obliquely to yethe basis ef; To my eye at O appeared a black spot (R) in yethe midst of yethe white basis (or filme of aire) ef, & to my eye at N appeared a white spot (R) in yethe midst of yethe black basis (or plate of aire) ef; through wchwhich spot (as through a hole in yethe midst of a black body) I could distinctly see any object, but could discerne nothing through any other parts of yethe appearingly blak basis ef. 29 By variously pressing yethe Prismes together at one end more ynthan at another I could make yethe said spot R run from one place to another; & yethe harder I pressd yethe prismes together, yethe greater yethe spot would appeare. to bee. [Soe ytthat I conceive yethe Prismes (their sides being a little convex & not perfectly plaine) pressed away yethe interjacent aire at R & becoming contiguous at R in ytthat spot, transmitted yethe Rays there in ytthat place as if they had beene one continuous peice of glasse; whereas yethe plate of aire ef is a very reflecting body: soe ytthat yethe spot R may bee called a hole made in yethe plate of are aire (ef)]. 32 The colours of yethe circles (in yethe 30th & 31th experiment) appeared more distinct at C ynthan at B, & to yethe Eye O ynthan to yethe Eye N. There being I conceive more colourlesse some colourlesse light reflected wthwith yethe coloured light to O, & C but much more colourlesse light transmitted to N & B; wchwhich must needs whiten & b whiten & blend the colours. Of Colours 30 In yethe 27th Experiment when yethe colour white or red was trajected on B, there would apeare severall circles of colours about. yethe black yethe white spot at B & also about yethe darke one at C. But these colours vanished together wthwith yethe red colour at B: Growing greater & greater distincter untill they vanished. 31 Likewise in yethe 28th exper:experiment when yethe spot was in ytthat side yethe partition pq next yethe eye, it appeared coloured to my eye both at O & N, encompassed wthwith divers circles of colours. Wchwhich circles would grow greater & greater distincter by how much yethe coloured partition pq came nearer & nearer to ymthem (ytthat is by how much yethe base ef was more & more oblique to yethe rays) & soe vanished by degrees as yethe said limb pq came to ymthem. Before they began to vanish they appeared round or Ellipticall thus But in their vanishing (especially if looked on through a hole much smaller then my pupill) they appeared incurved thus. But I could see yethe most circles when I looked on ymthem through a long slender slit, for held parallel to yethe coloured limb pq, when yethe circles halfe disappeared: for ynthen I have numbered 25 red circles & blew ones esteeming each consecution of red & blew to bee one circle & could perceive ther were many more so close together ytthat I could not number ymthem; whereas wthwith my naked eye I could not discern above nine or ten red ones & as many blew. 33 The circles are yethe broadest nearest to yethe center & so beeing narrower & narrower doe (I conceive by yethe exactest measure I could make) increase in number as yethe interjacent aire doth in thicknesse. (Sit cd = radio curvitatis vitri; efghik circuli colorum; & el =

\frac{fm}{2}

\frac{gn}{3}

\frac{hp}{4}

\frac{iq}{5}

\frac{kr}{6}

= crassitiei æris). And this I observed by a sphericall object-glasse of a Prospective tyed fast to a plaine glasse, so as to make yethe said spot wthwith yethe circles of colours appeare Of colours. 34 By the forenamed Prospective glasse I observed (though not very exactly) ytthat yethe more obliquely yethe ray tc was incident to yethe filme of aire ef twixt yethe glasses, yethe greater yethe coloured circles are in this proportion: Viz: as yethe summe of yethe factus of yethe motion of yethe incident ray into its velocity perpendicularly towards yethe aire ef & of yethe factus of yethe motion of yethe ray said ray in yethe aire ef into its motion perpendicularly through yethe said aire is to yethe said factus when yethe incident ray is perpendicular, soe soe is yethe bignesse of yethe coloured circles wnwhen yethe incident ray is perpendicular to yethe bignesse of yethe same circles wnwhen yethe incident ray is oblique, soe is dd x cv + ee x cs to dd + ee x ct. But yethe spot in yethe midst is not made greater or lesse by yethe obliquity of yethe rays rather yethe contrary 35 When yethe rays were perpendicular to yethe aire ef, yethe diameter of 5 of yethe circles was one parte, whereof 400 was yethe radius dC of yethe glasses curvity. the said radius being 25inches Soe ytthat (el) yethe thicknesse of yethe aire for one circlescircle was

\frac{1}{64000}

inch or 0,000015625. [wchwhich is yethe space of the pulse of yethe vibrating medium.] by measuring it since more exactly I find

\frac{1}{83000}

= to yethe said thicknesse. 36 Accordingly as yethe glasses are pressed more or lesse together yethe coloured circles doe become greater or lesse. & as they are pressed more & more together new circles doe arrive in yethe midst untill at last yethe said pellucid spot R doth appeare. 37 The circles of colour appeare in this order from yethe center to yethe eye O Or on yethe paper at C viz Darke (or pellucid), white, yellow, greene, blew, purple, Red, yellow, greene, blew purple, Red, yellow, Greene, blew &c. But to yethe eye N or on yethe Paper at B they appeare in this order Light (or pellucid) black, blew, Greene, yellow, Red, purple, blew, greene soe ytthat those circles wchwhich appeare Red to yethe eye O, appeare blew to yethe eye N, & thos wchwhich appeare blew to yethe eye O appeare of yethe contrary colour red to yethe Eye N Of Colours. 38 Those circles wchwhich appeare Red to yethe eye O, & blew to yethe eye N are almost as broade againe as those wchwhich appeare blew to yethe eye O & Red to yethe eye N. 39 Holding yethe said circles in a darke roome in yethe blew rays made by a Prisme (as yethe 10th Experiment) all yethe said circles appeadappeared blew but those wchwhich in yethe discoloured light appeared red appeared of a blew much more diluted ynthan yethe others. And if yethe Red Prismaticall rays fell upon those circles yethe all yethe circles appeared red but those circles wchwhich in yethe clear light appeared blew, in yethe Prismaticall red rays appeared of a much fainter darker & obscurer red ynthan yethe others. 40 Whither these circles were held in yethe Prismaticall blew or red rays they still appeared of yethe same bignesse. 41 Putting water betwixt yethe two Prismes instead of yethe fill filme of aire; There appeared all yethe Phænomena of yethe said circles, & also of yethe 22, 23, 24, & 25t Experiments &c. Onely somewhat more obscurely becaus there is lesse refraction made out of glasse into water ynthan into aire; & yet 42 The coloured circles appeared as big when there was a filme of water as when there was a filme of aire betwixt yethe Prismes. 43 If you make yethe pellucid spot R nimbly to run to & fro. There will appeare another spot S to follow it, wchwhich spot S exhibits such Phænomena as it ought to doe were it a Spot of aire, viz: To yethe eye O it appeares white next yethe Spot R & ynthen yel Red &c, But to yethe eye N it appeares black next yethe Spot R & ynthen blew &c: wchwhich colours it ought to have were it a filme of aire (by experexperiment 37). But it is not a filme of aire because if yethe Spot R rests a little, the water creepes into yethe said spot S & makes it vanish. It seemes therefore ytthat yethe water cannot nimbly enough follow yethe spot R, but leaves Of Colours yethe space S empty to bee possessed by Æther alone, untill yethe water have time to creepe into it. 44 Refracting yethe Rays through a Prisme into a darke rome (as in yethe 7th Experiment) And holding another Prisme about 5 or 6 yards from yethe former to refract yethe rays againe I found ffirst ytthat yethe blew rays did suffer a greater Refraction by yethe second Prisme then yethe Red ones. 45 And secondly ytthat yethe purely Red rays refracted by yethe second Prisme made noe other colours but Red & yethe purely blew ones noe other colours but blew ones. 46 If three or more Prismes A, B, C, bee held in yethe sun soe ytthat yethe Red colour of yethe Prisme B falls upon yethe Greene or yellow colour of yethe Prisme A & yethe Red colour of yethe Prisme C falls on yethe Greene or yellow colour of yethe Prisme B; yethe said colours falling upon yethe Paper DE at P, Q, R, S. There will appeare a Red colour at P & a blew one at S but betwixt Q & R where yethe Reds, yellows, Greenes, blews, & Purples of yethe severall Prismes are blended together there appeares a white. 47 Or if you clean a peice of Of Colours Paper on one side of yethe Prisme wthwith severall slits a, b, c, d, in it parallel to yethe edges of yethe Prisme soe ytthat yethe light passing through those slits make colours on yethe Paper DE; If yethe said paper be held neare to yethe Prisme there will appeare for each slit a, b, c, d, a coloured line r, s, t, v. The paper being held farther of untill yethe said coloured lines bee blended together, there will appeare white twixt p & q where those colours are blended; at m there appeares Reds & at n blews. But if yethe paper bee still held farther iof the white colour (pq) will appeare narrower & narrower untill it vanish. & then gh on one side appeares Red & gf on yethe other side is blew. 49 A single superficies of Glasse reflects many rays whither they passe out of glasse into aire or out of aire into Glasse & yet two surfaces of Glasse when contiguous (by yethe 27th 28th & 29th Experiment) reflect yethe Rays noe more then if the glasses had beene one entire peice wthwithout such a superficies betwixt ymthem. 48 As white was made by a mixture of all sorts of colours (in yethe 46th & 47th Experiment) Greene is made by a mixture of blew & yellow, purple by a mixture of red & yellow, &c 50 Thin fflakes of Muscovy Glasse, Bubbles wchwhich children make of sope & water, yethe thin skums of l molten leade, of cooling iron, water wiped very thin on glasse, glasse blowne very thin, &c represent yethe Phænomena of yethe coloured circles in yethe 30th and 31st ExperExperiment &c. To wchwhich may bee referred coloured motes in yethe Sun or in liquors, or pouders, or sollid bodys; yethe slender coloured threds of some cobwebbs, of silke wormes, & of flax finely dressed in them (though yethe flax in spining loseth its glosse, because yethe flat thredds cleave together againe into two greate a thicknesse see ExperExperiment 49 ) 14Of Colours 51 If yethe Sun S shine upon a large glasse Globe abd filled wthwith water And if youryou hold your eye very neare to yethe globe, yethe rays bp will appeare coloured redd & yethe farther you hold yoryour eye from yethe glasse yethe lesse they appeare coloured, untill yethe colour vanish. But yethe Rays rd & fq appeare coloured at wtwhat distance so ever yoryour eye bee placed from yethe Globe. The like you may observe by letting yethe colours fall on a peice of paper. 52 Though one termination of light trajected through yethe Prisme will not make both blews & reds; yet in this globe it doth (see Cartesij Meteora cap 8 sec 9) ffor yethe rays rd & fq make all sorts of blews & reds; indeed by yethe rays bp yethe red is very distinct but yethe blew is scarce discernable. 53 The colours of yethe Rainbow must bee explicated by yethe rays rd & fq (vide Cartesij Meteor Cap 8 sec 1, 2, 3, 9, 10, 11, 12, 15) ffor yethe bow may bee mad by drops of water forcibly cast up into yethe aire. 54 The spot R (mentioned in ExperimntExperiment yethe 52d) grows lesse or lesse by how much yethe rays fall more & more obliquely on yethe intermediate filme of aire ef. [wchwhich seemes to intimate ytthat yethe thinness of yethe intermediate filme of aire (or rather Æther) augments its refraction, untill (when yethe glasses become contiguous) it bee equall to ytthat of glasse] 55 The surfaces of Glasse doe not reflect soe much light when yethe glasse is in water as when it is in aire & yethe lesse any two mediums differ in refraction yethe lesse their intermediate surface reflects light [wchwhich intimates ytthat tis not yethe superficies of Glasse or any smoth pellucid body ytthat reflects light but rather yethe cause is yethe diversity of Æther in Glasse & aire or in any contiguous bodys though yethe parts of yethe Glasse must necessarily reflect some rays. Of Colours 56 The pouders of Pellucid bodys is white soe is a cluster of small bubles of aire, yethe scrapings of black or cleare horne, &c: [because of yethe multitude of reflecting surface soe are bodys wchwhich are full of flaws, or those whose parts lye not very close together (as Metalls, Marble, yethe Oculus Mundi Stone &c) whose pores betwixt their parts admit a grosser Æther into ymthem ynthan yethe pores in their parts]. hence 57 Most Bodys (viz: those into which water will soake as paper, wood, Marble, yethe Oculus Mundi Stone, &c) become more darke & transparent by being soaked in water [for yethe water fills up yethe reflecting pores] 58 If wthwith a bodkin gh 58 I tooke a bodkin gh & put it betwixt my eye & yethe bone as neare to yethe end of Backside of my eye as I could: & pressing my eye wthwith yethe end of it (soe as to make yethe curvature a, bcdef in my eye) there appeared severall white darke & coloured circles r, s, t, &c. Which circles were plainest when I continued to rub my eye wthwith yethe point of yethe bodkin, but if I held my eye & yethe bodkin still, though I continued to presse my eye wthwith it yet yethe colours circles would grow faint & often disappeare untill I renewed ymthem by moving my eye or yethe bodkin. 59 If yethe experiment were done in a light roome so ytthat though my eyes were shut some light would get through their lidds There appeared a or redish spot in yethe midst at greate broade blewish darke circle outmost (as ts), & wthwithin that another light spot srs whose colour was much like ytthat in yethe rest of yethe eye as at k. Within wchwhich spot appeared still another blew spot r, 16Of Colours especially if I pressed my eye hard & wthwith a small pointed bodkin. & outmost at vt appeared a verge of light 60 But on yethe contrary if I tryed yethe experiment in very darke roome yethe circle ts apeared of of a Reddish light sr of a darkish blew & yethe middle spot r appeared lighter againe; & there seemed to be a circle of darke blew tv wthwithout yethe circle ts yethe outmost of all [I conceive (in yethe 60th experiment) where yethe curvature of yethe Retina at ma & fn began & was but little yethe blew colour tv was caused; at ab & ef where yethe Retina was most concave, yethe bright circle ts was caused: at bc. & de where yethe Retina was not much incurved nor strained yethe darke blew circle sr was caused & at cd where yethe Retina was stretched & made convex yethe light spot r appe was caused. In yethe 59th Experiment yethe spirits were str perhaps strained out of yethe Retina at ab, ef, & cd or otherways made incapable of being acted upon by light & soe made darker colours a lesse appearance of light ynthan yethe rest of yethe eye Retina] 61 That yethe same circle ts wchwhich appeared light in yethe darke, appeared darke in yethe light I could found by remain suddenly letting in light into a darke darke roome for ynthen yethe bright circles would imediatly turne into darke ones & darke ones into bright ones. 62 I could sometimes perceive vivid colours of blew & red, made by yethe said pressure & perhaps a criticall eye might have discerned this order of colours. in yethe 60th experiment viz from yethe center greene, blew, purple, darke purple, blew, greene, yellow, red like flame, yellow, greene, blew, bradebroade purple, darke. 63 Looking on a very light object as yethe Sun or his image reflected; for a while after there would remaine an impression of colours in my eye: viz: white objects looked red & soe did all objects in yethe light but if I went into a dark roome yethe Phantasma was blew. 64 That vision is made in the retina appeares because colours are made by pressing the bakside of the eye; but when yethe eye turns towards yethe pressure, soe ytthat it is pressed before yethe colours cease.

Of Colours. The Tunica Retina grows not from yethe sides of of yethe opticksoptick nerv (as yethe other two wchwhich rise one one from yethe dura, yethe other from yethe Pia mater) but it grows from yethe middle of yethe nerve sticking to it all over the extremitys of its marrow. Which Marrow if the nerve bee any where cut cross wise twixt yethe eye & yethe union of the nerves, appeares full of small spots or pimples, wchwhich are a little prominent, especially if the nerve be pressed or warmed at a candle. And these shoot into yethe very eye & may bee seene wthwith in side where yethe retina grows to yethe nerve: and they also continue till to yethe very juncture EFGH. But at this juncture they end on a suddein into a more tender white pap like the interior part of the braine & soe yethe nerve continues after yethe juncture into yethe braine filled wthwith a white tender pap in wchwhich can bee seene noe distinction of parts as of betwixt yethe said juncture & yethe eye. Now I conceive that yeevery point in the retina of one eye hath its correspondent point in yethe other, from wchwhich two pipes very slender pipes filled wthwith a most lympid liquor doe wthwithout either interuption or any other uneavenesse or irregularity in their processe, goe along the optick nerves to yethe juncture EFGH where they meete yethe one halfe either twixt GF yethe other twixt or FH, & there unite into one pipe as big as bothe of them, & so continue in one passing either twixt IL or MK into yethe braine where they are terminated perhaps at yethe next meeting of yethe nerves twixt yethe Cerebrum & cerebellūum, in yethe same order that their extemities were scituate in the Retinals. And so there are a vast multitud of these slender pipes wchwhich flow from the braine the one halfe through the right side nerve IL till they come of the juncture GF where they are each divided into two branches the one passing by G & T to yethe right side of yethe right eye AB, the other halfe shooting through yethe juncture EF & soe passing by X to yethe right side of the left eye αβ. And in like manner the other halfe shooting through the left side nerve MK divide themselves at FH & their branches passing by EV to the right ey & by HY to the left, compose that

\frac{1}{2}

of the Retina in both eyes wchwhich is towards yethe left side, CD, & γδ. Hence it appears i why yethe two images of both eyes make but one image abcd in the braine. 2 Why when one eye is distorted objects appear double, ffor if yethe image of any object bee made upon α in the one ey & β in the other, ytthat object shall have two images in the brain at a & b. Therefore the pictures of any object ought to bee made upon the corresponding points of yethe two Retinas if upon A in yethe right ey then upon α in yethe left. If upon B then also upon β. And soe shall yethe motions concurr after they have past yethe juncture GH & make one image at a or b more vivid then one ey alone could doe. 3 Why though one thing may appeare in two places by distorting the eye yet two things cannot appear in one place. If the picture of one thing fall upon A & of another upon α, they may both proceeproceed to p but noe farther, they cannot both be carried on yethe same pipes pa into yethe braine, that wchwhich is trongeststrongest will there or most helped by fantasy will there prevaile & blot out yethe other. 4 Why a blew seene by one eye & a yellow by the other at yethe same time produces a greene unlesse yethe fantasy make one colour prædominant. 5tly Why if one of the branches of yethe nerve beyond yethe juncture as at as at GF or FH should bee cut: That halfe of both eys toward yethe wounded nerve would bee blind, the other halfe remaing perfect. 6tly Why the juncture is broader almost as broad again twixt G & H then twixt E & F, becaus all the tubuli of both eys pass twixt G & H & but

\frac{1}{2}

of them twixt E & F. It is not quite so broad again because yethe tubuli crossing in G are joining &c: also yethe thicknes of the quicks &c.7tly why the nerve GILF buts not directly upon the nerve XEHY but in little transcends a deviates a little towards TV because its Tubuli are to passe only into that side of the nerve EHYX towards EX. The like of FMKH 8thly why the marrow of the nerve TVEG grows soft on a suddein when it comes at the juncture EF & more suddenly on that side towards G then towards E. And the like of the nerve EXYH. For it being necesary that the nerve TVEG should bee stretcht & bended severall ways by the motion of the eye: Therefore the tubuli are involved in severall to or wrought up wthwith in the substances of severall tough skins wchwhich being foulded up together compose yethe marrow of yethe nerve, pretty sollid & flexible least yethe tubuli should be prejuced by the severall motions of the nerve. And those small pimples or prominences wchwhich appeare in the nerve cut crosse wise I conceive to bee of made by the foldings of these crasser skins. But the nerve at yethe juncture EGFH being well guarded from all violence &c. 19 motion caused by the motio by the bones into wchwhich it is closely adapted: tis not necessary the said membranes substance should be continued any further then EG therefore the tubuli there on a suddein unsheath themselves there on yethe inner side of the nerves towards VE & XE may severally crosse twixt EF & bee united wthwith their correspondents on the other sides YH & TG. Now because yethe inner tubuli must first crosse before they can convene wthwith the outmost tubuli of the opposite nerve hence it is that yethe nerves grow soft sooner on yethe inner side at E then on yethe outer side at G & H. 9thly why yethe two nerves meet a second time in the braine, because yethe two half images caried along IL & MK may bee againe unite united into one complete image in the sensory. Note ytthat yethe nerves at their contact meeting are round about disjoyned from yethe rest of the braine, nor are they soe thick theire as a little before their meeting. But by their externall figure they seeme as if the capillamenta concentered like yethe radii of a hemisphere to a point in yethe lower part of the juncture. And tis probable ytthat the visive faculty is there for else why doe the nerves swell there to so great a bulke as it were preparing for their last office, why doe they run directly crosse from eithersideeither side the braine to meet theirthere if theythe designe was they might not cumber by to have yethe motions coveyed by the short cut from yethe eye to yethe sensoriūum before they grew too weak. If they were to proceed further their meeting their swelling to so great a bulke, they might have gone a shorter cut & in a lesse channell. There is indeed a marrow shoots from under them toward yethe cerebellum to wchwhich they are united but yethe greatest part of their substance if not all of it shoots lys above this marrow & also shoots cross beyond it to yethe center of the brain where they meet. Lastly the substance here is most pure, yethe scituation in yethe midst of the brain, & where they constituting yethe upper part of that small passage twixt all yethe ventricles. where all superfluous humors have the greatest advantages to slide away that they may not incumber ytthat prciousprecious organ Light acts not upon seldom striks upon yethe parts of grosse bodys (as may bee seen in its passing freely through them), its reflection & refraction is made by yethe diversity of æthers, & therefore it effectesits effect on the Retina can only bee to make this vibrate wchwhich motion then must bee either carried in pupil yethe optick nerve to yethe sensorium or produce other motions that are carried thither. Not yethe latter for water is too grosse for such subtile impressions & as for animall spirits though I tyed a peice of yethe optick nerve at one end & warmed it in yethe middle soto see if any aery substance by that meanes would disclose it selfe in bubbles at the other end, I could not spy the least bubble; a little moisture only & yethe marrow it selfe squeezed out. And indeed they that know how difficultly aire enters small pores of bodys, have reason to suspect ytthat an aery body though much finer then aire can pervade easily & wthwithout violence (as it ought to doe) yethe small pores of the braine & nerves, I should say of water, because those pores are filled wthwith water, & if it could it would bee too subtil to bee imprissoned by yethe dura mater & Skull, & might passe for æther. However, bee those spirits wtwhat need of such spirits much Motion is ever lost by communication especially twixt bodys of different constitutions. and therefore it can noe way bee conveyed to yethe sensorium so entirely as by the æther it selfe Nay granting mee but that ther are pipes filld wthwith a pure transparent liquor passing from yethe ey to yethe sensoriūum & yethe vibrating motion of yethe æther will of necessity run along thither. ffor nothing interrupts that motion but reflecting surfaces, & therefore also ytthat motion cannot stray out of its pipe through yethe reflecting surfaces of yethe pipe but must rush along (like a sound in a trunk) intire to yethe sensorium. And that vision bee thus made is very conformable to the sense of hearing wchwhich is made by like vibrations. ffrom yethe whitenes of the brain & nerves the thicknesse of its vessells may be determined & their cavitys guessed at. And its pretty to consider how these agree wthwith the utmost distinctnesse in vision. As also wthwith yethe intent of nature in conveying yedistinctly yethe motions of the aetherAether. Of colours If rays be incident out of glasse upon a film of of air terminated twixt two glasses, the thicknesse of a vibration is

\frac{1}{81000}

, or

\frac{1}{80000}

part of an inch If water was put twixt the glasses the thickness of a vibration was

\frac{1}{1000000}

inch, of

\frac{3}{4}

of its former dimensions. viz as yethe densitys of the interjected mediums. If yethe rays were incident obliquely, the circles increase so that their diameters are as yethe secants of the rays oblique incidence on yethe sphericall film of aire obliquity wthwithin the film of air, or reciprocally as their celerity wthwithin the said film. And the thicknesse belonging to each vibration is as the squares of those secants of celeritys, And yethe lengths belo of yethe rays belonging to each vibration as their cubes. The first pulse ends at the first dark circle The thicknesse of a pulse of extream rubiform rays to that of purpuriform ones perpendicularly incident is greater then 3 to 2 & lesse then 5 to 3. viz as 9 to 14 or 13 to 20. And the thicknesse belongsbelonging to each coulour is 13, 14 14

\frac{1}{2}

, 15

\frac{1}{2}

\frac{1}{2}

. 17

\frac{1}{2}

. 18

\frac{1}{2}

. 19. for extreame purple, intense purple, Indico, blew, green, yethe terminus of green & yellow, yellow, orange, red, extream red. Mr Boyle mentions one that by sickness became so tender sighted as in yethe dark night to see & distinguish plainly yethe colours of ribband (& other objects) on purpose pinned on yethe inside of his curtains against he awaked. Of yethe determinate nature of Effluviums p 26, And of another ytthat by a feaver became of so tender hearing as to hear plainly soft whispers at a distance wchwhich others could not allat all perceive, but when he grew well his hearing became but like ytthat of other men. Ibid. Stipic vegetables, as gall, oaken bark, red roses, Logwood, Sumach &c turn vitriol to a black precipitate