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Show M" >_,__.--.-~--------\ 0f Seeing. 896 Book Ill. Book III. 0f Seeing: 397 ; E. V ‘ ' But w enee d n o t a n y farther ex p eri in e ut fe tchedirom Art, when Nature Abram", Ray is only to be excepted, which cometh perpendicularly in a right Line ‘ to the Axis of the Eye, without any Refraction. it felf, the ground of Arts and Sciences giveth us an infiance upon this fup- P‘°""S‘h= pofition; That the Left fide of the Pupil is clouded by a Sufftiiion, or a :‘ftfiiiiiimn Membrane finding it 3 whereby the vilible Ray cannot be freely tranfinit- (Rflrsumtil To illnfirate this Hypothefis, I make bold to offer this Inftance, If the An Experimotto make Eye be fliaded with a thin opace Plate, perforated With a fmall hole, through hi‘ihi‘iyl- which the vifiblc Object, feated beyond the Plate, may be tranfmitted, red from the Left part of the Object, which intercepteth the progrefs of the MC" ‘ and recommended to the Pupil of the Eye by RayS, interf€&ihg each other Left oblique Rays ; fothat it cannot meet the Right, and interfeét it: Hence the vilible images of things change their true fituarions, and the objeé‘ts are prefented to the Eye in undue politions, not fuitable to the nature ofthings. at the hole of the Plate, vailing the Eye', Wthll may be confirmed by this Experiment; That ifa thin little Plate ( being placed between the Eye and greater Plate > be moved gradually toward the hole, the point of the vifihle By teafon the point reflecting the vifible Hay cannot be feen in a Right, Objeét may be difcoverecl to be obfcured, before the little Plate toucheththe , . _ hole on that fide. Becaufe no point of a vilible Obyeét can be .obfcured by the interpolition but an oblique Line, as the object is blinded by a lEmi-circular opace Bo- dy (feated in the Left part of the Pupil) hindring the point of the Ray, that it cannot fall upon the Left fide of the Sight of the Eye, thereby milling the interfeétion of the Rays, and petverting the due order of Sight, of fame Body,unlefs the point of the Ray be intercepted 5 whence it follow. eth ofneceflity,that the Ray cometh fromthe porntofthe Obyeét upon thelit. tle Plate,by reafon the point is there fitfl obfcured, when the Plate is brought toward the hole of the other Plate, intercepting the Ray refleé‘ted from [he Object in a direct progrefs. rm manic ' _ This Experiment proveth the decuflation of vihble Rays, becaufe in the difalfeéted Eye, if any object be prefented to it in a direct Ray, falling about the Axis of the Eye, the vifible Image is wholly oblciired, and not at all capable to be difcerned, by reafon the obliquenefs of the Incidence and Refraction 3 lo that a part ofthe pupil of the Eye, covered with a dark Bo- . Wherefore if two Rays reflected froma Vifible Object, {hould not inter- iiiiliringifim. feét each other near the Pupil of the Eye, they mufl: mutually . aflociare'in dy, cannot fee objeétsdireé‘tly oppolite, but feated on the other lide ; wherefore itmay be determined, that the Rays fireaming from the Objeét, as in- :fiffikh their progrefs, which is inconfil'tent With the nature of tight Lines, which iijc'ffmm mull run parallel, or elie right Lines mul't contain Angles, which contra- terfeciing each other, are carried into the \vell-difpofcd pupil of the Eye. Thus Ihaving given an account how the lucid Rays (apparclling the The Inter- iiiié'tirlhgiic diéieth the received principles of Mathematicks; 10 that by conlequencc, m" the vifory Rays mufi interfeét each other, if they be fuppofed to take their courfe in right Lines. 1 its," pm. pi itiy ct‘iuc nyetimcnt, The Stconil. femblances of outward Objects) interfefi each other near the pupil of the fictiiii'élh‘? Eye, that the faces of objects may be clearly prefented to the Eye in right 9:33:12" f order, and due fituation according to the nature of things iii: 651321 in And now my aim is to {hew you how Rays are trajeéted through various Effigy and Mediums, asendued with divers degrees of Rarity and Denfity; whereuPon Rays lofing their direct progrefs ( as they receive greater orlefa telifiance from different Mediums through which they pafs) do make greater or lefs Angles; {‘0 that the Rays are tranfmitted through the tranfparent Coats This Experiment may feem to be qualified with divers proprieties, (as Learn- ed Scbeiner hath obferved ) Firfi, that the point of the vifible Object is much fliaded by the little Plate, and its fituation difordred, the Right part being turned into the Left, andthe Left into the Right, and the Upper below, and the lower above, which is caufed by the right progrefs of the Rays, whofe interfeéiion being intercepted by the interpofition of the little Plate, thetruc lituation of the Obieéi is perverted. Secondly, if the hole ofthe Plate be made large, and the fmall Plate being interpofed near the Eye on the Right fide, the Left part of the hole will and Humors of the Eies, difl'ering in Situation, Figure, and Denfity, Where- upon it follows of neceflity, that the Rays muflt reccde from their right progrefs, and fufiEr Refraction. be obfcured, and the Right remain open and free 5 but if the lefs Platehfi moved beyond the greater, f0 that it cloudeth half or more of the holeylhc Left Ray will be hid which happens, becaufe the Ray refleéted obliquely The Third propriety of thc Inflaiite. Wherefore feeing the various parts of the Eye have a different rarity and denfity, and moi} of their furfaces are excentrick, as relating to each other; from the Right part of the vil'ible Object, and tranfmitted to 'the Right fidc Therefore the Rays pafling the Cornea, mui'c be refrafled, f0 that the Sight muft be made either in the Convex Surface of the Cornea, if it be celebrated of the hole, doth make a greater Appulfe on the Right fide ofthe Eye, than that Ray, making its progrefs to theleft part of the hole, which dead5 by ffraught Rays, or elfe if the fubjeét of vifion be feated in the more inward recelles of the Eye ( which I [hall endeavour to prove hereafter) the Rays being carried through dimmilar Mediums,mui't admit refraction, whence it the aétivrty of the Right Ray, from whence it may be evinced, that themterfeé‘tion ofthe Rays of the Sight, give a clear perception on every part 0f muPt reafonably be inferred, that Sight cannot be made by direct Rays with the pupil of the Eye. Thirdly, :4 Ray proceeding from the Right lide of the Object, dorh fall the Convex Surface of the Cornea. Every lucid Ray ( according toa natural Principle) doth move Hemif. The right upon the l cft part of the Pupil of the Eye, and the Ray coming from the phaerially, and falling upon the Cornea of the Eye, doth irradiate the whole 5,3333%. Left part of the Objec'r, upon the Right region of the Pupil, and the up?" Circumference of its Convex Surface, which rcceiveth a brisket appulfe my" °b‘ part of the Objeé‘t falling upon the lower, and the inferior upon the tOP ° ffom a Bay moving in a right, then oblique Line ; f0 that upon a fuppofition being made, that the act of Seeing is accomplilhed in the Surface ofthe the Pupil of the Eye ', whereupon the mutual interfeétion of the vifible Rays do confiitute the feveral parts of the Object in a due fituation, which file would be reprefented to the Eye in great diforder, in an unnatural pom!" cpnfounding the Sight, as not receiving its Object, according to its tru€ p ace. i Carma; it mui't be granted, that a Ray coming from a vifible point, and mao'tlflg its progrefs at right Angles, is the moi} flrong, as over-powring ers. .B)' reafon the Tunicle of the Cornea is outwardly prominent, as cndued With an orbicular Figure, whence it is co‘nfpicuous ,that a vifible pointdfl'eatfd But ireét y |