OCR Text |
Show Book lll, ‘ Cones. This Humor is Convex in the lower Surface, and its whole Perimc. ter is encircled with a fine tranfparent Tunicle, called Vitrea, feVering it from the Crifialline Humor, and boundeth its more finide Particles, and fecureth it from intrenching upon the neighbouring parts. The Vitreous Humor deriveth its firit produéiion from femiual Liquor, , which confiiiing of thin and fluide Particles, hath a loofe Compage, caiily recep'tive of Light, whofe fubtle aethereal Particles make many arrangmenrs through its ambient parts, and more inward Receifes, giving it a clearnefs and Tranfparence, which is endued with a power to receive the Vifoiy l Rays, and tranfmit them to the Retina. Book III. Of Light in err/er to Seeing. 89 i direé‘t retrograde motion in Refleélion, _or an oblique Current in Refraé‘rion. Rays being a great company of continued ltiCid Particles "(to fpeak Phi‘1 . lofophically ) are adorned with a Priimatick or Cylindrical Figure, by "3: igéiycisgt.ici {on many minute Bodies being'feated in the Surfaceof ‘a greater or leis luminary (from which :1 Ray 15 propagated) al‘ecal‘l‘lt‘d from their prime place or Bafe, by prefling right forward through a contiguous Body, which complieth in Figure to the iliape of the iinpelling Body,‘which is long3 fun" and round ( founded originally in the‘ Surface of a lucid-Oil) ) or ifyou pleafe, it may be conceived fomewhat to refemblcaCylinder, or .Prilme, as fome Mathematicians will have it; or thefe Rays may be deicribed by right Lines, as they are very long narrow Bodies; And itdorh not at all deitigate from the Science of Mat‘hematicks, to take their Axes or Perpendi- culars to be afic&ed with Cylindrical or Prifmatick tigurcs. ‘ Another Hypothefis relating to Light, may be this, That a Ray l3 propa-F CHAP. VI. , gated Hemifphxrially from every point of a luCld Body, to all points 0. aim," _ the Medium, unlefs it be darkened With an Opace Body, intercepting the iii;q:ii.«;n.i-;, of Li ht. bmhnrid byg the points referring to the lucid Body, and the, Diaphanous Medium, we are not to tinderl'tand' than), to be purely Mathemati- 1,0,?"th Of Light in'om'er to Seeing. HAving given you a Hifiory of the Fabrick of the Eye (as compofed of variety of Tunicles and Humors, as fo many Circles encompafting each other, and making up the elegant Globe of the Eye) I willnow endeavour to explain the ufe of this tranfparent Orb, how its feveral parts,encircling each other, are minifierial to Sight, by giving us a fine Vifeto of various images of things, as f0 many Pictures, confiiiing of beau. tiful Figures and Colours, arrayed with beams of Light, refleéied from Opace Bodies, Firfi in right Lines, and afterward tranfmitted by manyinterfeétions, and inflections, making divers angles of incidence and refractions in Heterogeneous and Exentrick Diaphanous mediums of the Eye, and are at laft imprinted on the Organ of \ ifion. A lucid Body may be fuppofed a S} Preme of innumerable Atomes, of which every one is acted with a moii fwift motion, propagated in right I ines through the ambient fluid Medium, whofe Particles being free from firm connexion, are befet with an infinite number of Pores, receptiVC mofi minute Bodies of Light, which being oppofed by fome folid opacc Body, do recoil inward into themfelves, and being confined within their own bounds, are not difiipated, as expanded by crooked lines but continue their moi! rapid current in a direct courfe, into a fluid 30in as putting by {irong Appulfes any Heterogeneous Body into flight, that doth not make ‘09 powerful a refif'rance. ‘ An infinite company of thefe lucid Particles being clofely coniOYned to each other, and diiiiifed a great fpace in right lines, are called a Ray, Whid‘ I 90:36:qu to be made, when the Medicine is Homogene ous ( as qualifield Wittea meFiur ei fimilar Interfiicegs, , Mannitud 0‘ e and Solidity) " ' pervioiis ' by innumem b‘ But if the Medium be difpofed with Particles of a different fhapf‘, "1": or [00 great DpaLc Body. a Confidence, or too narrow Pores, (which do not readily, 0" no! at . _all receive the Atomes of Light) the freedom of their motion in right Lines is impeded, , . whereby they are forced to form Angles; fo that they makeé: dire cal, but mofi fmall Phyfical points, as minute as can be imagined; and that yni Shim the moii fubtle Atomes oi Light, moving With a anfl: wonderful qnick- 11:0" nefs, cannot be tranfmittcd from a lucid Body, through a ti‘aiifparcnt Me- mi, diuin at a great diitance in a moment, {ii-iétly taken, but in a minute portion of time, becaufe we cannot apprehend any fpace of it to be fo momental'y', butfome Ray may fircam from any Particle ofa lUCId Body, into , every point of the Medium, by reafon the Bafes or O'l'lgelis of thcfe ‘Rays, iii}: Emil; conflituting the lucid Body, (as far as we can conceive their quantity by i?"".v""'",'"i,' Reafon and Senfe) are infinite in number, and mof't iinall in quantity, and g,‘t‘:a,{‘,:§;fl, mofi agile in motion; and that in every point ofa luad Body, there are mnemonan innumerable company of lucid Atomes, difplaying themfelves into all coafisof the Hemifphazre in a mod fhort, and almofhiinperceptible fpacc of time, but not in an inflant rigoroufly taken, which 13. very improbable, if not impofiible, as fuppoiing many minute Bodies of Light, which implieth a contradiéiion, that the Pores of a tranfparent Medium [liould receive an infinite company of Atomes of Light in the fame infiant. _ This Hypothefis may be confirmed by many familiar Eitperirnents, and more efpecially by this 5 That in every place where the enlightened Qbyeéi flaring; isfeated directly oppofite to a Looking-glafs, a number of fubtle luCid Bo- fir")? "3' EP dies are reflected from every point of it, and conveyed to the Orbe of the 1'6"" C" . Crimea, the firi‘t tranfparent coat of the Eye. ‘ ' . Another Hypothefis belonging to Light, is, that its lines {tream perpendicularly, as they make an impulfe through the porous parts of the Medlllip, gigging, in nghtlines, either forth-right, as in Opticks, or in a~ retrograde cour e, m my," when it encounters an Opace Body ( affecting the Medium ) whereby the Rays of Light are reverberated into the contrary parts by refleétion, as in.Ca- "cm, topticlts,'or when they are inflected; making diHErent Angles in various $11. 1* », tranfi'arf-‘Ht Mediums, as in Dioptricks. _ a:-.,;hri _ ~ In a iimilar Medium not confifiing of variety of parts, as endued With :1, iii \ feveralMagnitudes, Figures, or too much Denfity, the Rays make their iif‘lfffi'f, motion in a firaight courfe, as not encountring any Heterogeneous Particles, ii'uii:,1;flied indifpoiing the Medium: WherenpOn the dreams of Light are. not dis/err- iiihisizia; ed from their proper Motion, right forward, by the oppofition of fomC unis. T {Q Opacc |