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Show M Book Ill. Of Seeing. m f,"- would make but an oh. mitted through the perforation of the Ila/ea, {cure and weal; impreiIion upon the Roma} but the appllcatlon of the clearly Criftalline Humor, near the Pupil of the Eye, makes the fpecres more _ . intcd u on the Otoan of Si ht. toward the Tricmrmmcf PaThe ILIZId Rays nziovingingpyramidal Figures, FirIt dircétly in everted progrefs their make it, beyond afterward and Wall, ‘3‘" MR}. hole of the . ' the Paper. Pyramids having greater Dimenfions toward In the fame form the Rays ( darted from every point ofa Vifible Obyea and hein right lines) are contracted witha Cone in the Pupil of the Eye, *ond'it have another everted Cone, which afterward are enlarged toward the Crifialline Humor and Tunicle of the Retina. . Art is perfcfiive of Nature, which may be illufttated by the reflected and a narrefraEted beams of Light (invefiing a vifible fpecres , pafiing through open more a Into Eye) the of Pupil the row hole , fomewhat refembling place, and grow more faint, as they obtain agreater freedom by parting from each other, and afterward become more {'trong, as. they are narrowed into a point in a Convex-Glafs, whereby the Ob)e& is more clearly . painted upon the adjoyning Paper in its hue and lineamenrs are muwhich Rays, vifual the with Analogy This lnftance hath much tually deeuilated, before they are entertained into the Pupil of the Eye, and nine are afterward tranfmitted to the Criflralline Humor, endued with a Convex form, that the intrornitted Rays being united and refracted, might be brought into order, and rendred more vivid, and regular, making thefemblance ofthe vilible Objeét more plainly and dii'tiné‘tly imprinted upon the filme of the (Retina. The Paper being placed too near, or too remote from the hole Without the common Bale of the Rays (conveyed to the hole) render the Image more OfSccing. Book III. 907 with pain, when the Object is placed too near the Eye, which is produced by its labour, when the vifive power endeavours to compofe and frame the Tunicles and Humors, which cannot be accomplilhcd without compreflion giving a pain and dif‘turbance to the tender and fine Compage of the Eye. ) To give a more clear underfianding of the notion of Sight, I Ihall en- Cmm'clflc deavour to make Art to run parallel with Nature, how Convex-Glades ih'rllr‘ucifjgiiif do aliilt and rectify the ill formation or Conftitution of the Criftalline Hu- iiiiniiilimm mot; and how one Convex-Glafs being added to another, doth render the common Bale ofthe vilible Image more near to the Glalles: So in like manner the Crilialline Humor hath lofl: much of its parabolical Figure, as brought toward a Plane, being [htuult up in old Men; whereby the cornmon Bafc of a vilible Object is carried too much inward beyond the Tunicle ofthe Retina 3 {0 that to help the ill Ihape ofthe Crifialiine Humor, old Men are conflrained to uleSpe&.1clcs, endued with a prominent Surface, that by a double Convcxity, relating to the Glafs, and Crilltalline Humor, the Bafe of the Piciure, belonging tothe Object might be contracted, and duely imprinted ou the Retina. And as a Concave-Glafs to a Convex, doth caufe the Rays carrying the Image of the thing7 to pals farther to the bottom of the Eye, which givcth an advantage to perfons, labouring with an over-much parabolical Figure ofthe Criltalliue Humor, determining the common Bafe of the femblance of a thing upon the \itreous Humor, productive of a confufcd Sight; as the vifual Rays do not reach the (Retina, which is much helped by Spectacles (euduedwith a Concave-Surface) tranfmittiiig the fpccies of the Object, confufed and ohfcurc: f0 after fome fort when the Rays being tranfmitted ‘ beyond the vitreous Humor, unto the coat of the Retina, the formal Organ of Sight. Having given in fome fort a Hiltory of Opticks, I lliall endeavour to asserting. through the Pupil of the Eye, have not a common concourfe or Bafe duly terminating into the Retina; whereupon the vifible femblancc of 2: thing {peak a period to this Difcoufe, in Ilicwinga Ihort model of Seeing; as Light dcmm‘m' acterh a great part in this vifible Scene, and may be Ptyled a Body made up is norclearly perceived, as the Retina is feared, either too near, or arm ofinuumerable lucid Particles, originally Itreaming from every point, and great a difiancc from the Cril'tallinc Humor, and Pupil ofthe Eye: And as ‘ carried into the minute pores of the/Ether, and Air, with molt nimble Morion, the Paper is placed at too little or too great a fpace from the Convex-GlalS, i iv and hole ofthe \Nall 3 whereupon the vifible fpecies is confufedly painted as the molt numerous Rays prefs each other forward with an inexpreflible U upon the Paper, which is-amended when the common Bafe, ( invel'ting the l'ifture) is orderly tranfmitted to the Paper, by the due fituation of it, in Cotiliiling of {mail Pores) is not receptive of lucid Rays; whereupon they being embodied with Images, as fo many EfHuxes of opace Bodies, make reference to the CorircX-Glafs and Hole 3 fo 2. great change is made ofthe full a kind of Arch, and afterward are reflected in right lines through a rcptelEntation of the vifible ()bjeét to the Eye by the variation of the place of the Retina, and Criflallinc Humor, in relation to the Pupil ; (0 that tl‘itidlle flurd Medium, befet with numerous {teams of adifferent Conliltence. The Light being difplayed through various Bodies , retaineth the poIture and Situation of their parts, and produceth feveral Schemes, according to the different Figure, and Texture of thofe parts of which they are fituation of the faidTnnicle and Humor, doth render the portraifture of ill: Obieét to be fairly painted. upon the fine Coat of the Retina, as the common Bafc ofthe vifual Rays do terminate upon it, at: $3511" And upon this account, Nature hath conferred a motive pOWer, both upon pm, "i [he the Tunicle ofthc Lima, and the Ciliary Proceifes, elevating and Contrafiing Drug and tiliavy mm, the Criltalline Humor, and when the too great concourfe of the lucid Ralf ' (clothing the vifible Object) is intercepted, the CriI'talIine Humor is comprel‘ fed,and made more Convex; or more Plane,by the relaxation of the ciliary Proceiles ; W hercupon the Rays ( invelting the vifible Images) become more or lefs refracted, as the Figure of the Crif'talline Humor is made more or 1‘33 prominent; and as the Retina is brought farther from, or nearer to the l" HlImOI‘i and to the Pupil of the Eye; that the (Retina may receive the com- 1 mon Bafe of the Image: thnce it conieth that the Eye is clifcompoffI WI" fwiftnels, till they meet with fome opace Body, which being compaét (as compounded ; f0 that the lucid Beams falling upon Opace Bodies , do by quicknefs of Morion, Energy , and feveral Refleétions, caufe va- Varictyof‘ riery of Apparencies, according to the different degrees of Rarity and 3,1111%; Denfity 0f feveral Mediums, afi'eéted with {trong and fainter Rays ; diffircntd‘f' pofitions of or according to feveral Afperities of dark Bodies, made up of great- diaglianous ‘T 0r lefs Cavrties, do produce divers Lights and Shades, the ground of Disclmrciv. . s . - N16 UmSA "QUOUS Colours, and Semblances of vilible Objects, which being cloth- Exam-233;: ed "'iill Rays of Light, are reverberated from opace Bodies, in a direct pro- fimgfc‘gm grcfs through the Air, to every point of the Cornea, where they are re- ceui'cd yy', traded) by making an Angle toward the perpendicular, as pafling from :1 332252331‘rare to a more denfe Medium, and having interfefled each other, as the $33: °r ‘ng Rays are carried to the Left, and the Left to the Right, elfe they Z I0 could |