Physiologia Epicuro-Gassendo-Charltoniana, or, A fabrick of science natural, upon the hypothesis of atoms founded by Epicurus repaired [by] Petrus Gassendus ; augmented [by] Walter Charleton ...

CHAP. III. Concerning the Manner and Reason of VISION. p. 149.

SECT. I.

ARTIC.

1 THe Reason of Vision, according to the opi∣nion of the Stoicks.

149

2 Of Aristotle.

150

3 Of the Pythagoreans.

ibid.

4 Of Empedocles.

ibid.

5 Of Plato.

ibid.

6 Of Epicurus.

ibid.

7 Of Mons. Des Chartes.

151

8 The ingenuity of Des Chartes Conceit, acknow∣ledged: but the solidity indubitated.

152

9 The Opinion of Epicurus more satisfactory, then any other: because more Rational, and less obnoxious to inexplicable Difficulties.

ibid.

10 The Two most considerable Difficulties oppo∣sed to Epicurus position, of the Incursion of Substantial Images into the Eye.

153

SECT. II.

ARTIC.

1 THat the superfice of no body is perfectly smooth: evicted by solid Reason, and Autopsie.

ibid.

2 That the visible Image doth consist of so many Rays as there are points designable in the whole superfice of the object: and that each Ray hath its line of Tendency direct, respective to the face of that particle in the superfice, from which it is emitted.

154

3 That the Density and Union of the Rays, com∣posing the visible Image, is greater or less; ac∣cording to their less, or greater Elongation from the Object.

ibid.

4 That the Visible Image is neither total in the total medium; nor total in every part thereof: but so manifold as are the parts of the medi∣um from which the object is discernable. Con∣trary to the Aristoteleans.

155

5 PARADOX. That no man can see the same particle of an object, with both Eys at once; nay, not with the same Eye, if the level of its Visive Axe be changed.

ibid.

6 CONSECTARY. That the Medium is not possessed with one simple Image; but by an Aggregate of innumerable Images, deradi∣ate from the same object: all which notwith∣standing constitute but one entire Image.

156

7 CONSECTARY. 2. That Myriads of different Images, emanant from different objects, may be Coexistent in the Aer; with∣out reciprocal penetration of Dimensions, or Confusion of particles: contrary to the Peri∣pateticks.

ibid

8 That the place of the visible Images ultimate Reception, and complete Perception; is the Concave of the Retina Tunica.

157

9 That the Faculty forms a judgement of the Conditions of the Object, according to the re∣presentation thereof by the Image, at its im∣pression on the principal part of Vision, the Amphiblestroides.

ibid.

10 CONSECTARY. That the Image is the Cause of the Objects apparence of this or that determinate Magnitude.

158

11 CONSECTARY. 2 That no Image can replenish the Concave of the Retina Tuni∣ca, unless it be deradiated from an object of an almost Hemispherical ambite.

159

12 Why, when the Eye is open there is alwayes pourtrayed in the bottom thereof, some one To∣tal Image; whose various Parts, are the Spe∣cial Images of the several things included in the visual Hemisphere.

ibid.

13 PARADOX. That the prospect of a shilling, or object of a small diametre is as great, as the Prospect of the Firmament.

160

14 Why an object appears both greater in Di∣mensions and more Distinct in parts, neer at hand, than far off.

ibid.

15 Why an object, speculated through a Convex Lens, appears both greater and more distinct; but through a Concave, less and more Con∣fused: than when speculated only with the Eye.

161

16 DIGRESSION. What Figur'd Per∣spicils are convenient for Old: and what for Purblind persons.

162

17 That to the Dijudication of one of two ob∣jects, apparently Equal, to be really the Great∣er; is not required a greater Image: but only an Opinion of its greater Distance.

163

18 Des Cartes Opinion concerning the Reason of the Sights apprehending the Distance of an object:

164

19 Vnsatisfactory; and that for two considerati∣ons.

ibid.

20 And that more solidone of Gassendus (viz. that the Cause of our apprehending the Di∣stance of an object, consisteth in the Com∣paration of the several things interjacent be∣twixt the object and the Eye, by the Ratio∣nal Faculty) embraced and corroborated.

ibid.

21 PARADOX. That the same Object, spe∣culated by the same man, at the same distance, and in the same degree of light; doth alwayes appear greater to one Eye, than the other.

165

22 A second PARADOX. That all men see (distinctly) but with one Eye at once: contrary to that eminent Optical Axiom, that the Visive Axes of both ey•• concur, and unite in the object.

166

23 The three degrees of Vision, viz. most per∣fect, perfect, and imperfect: and the verity of the Paradox restrained onely to the two former Degrees.

167

SECT. III.

ARTIC.

1 A Research into the Reason of the different Effects of Convex and Concave Glas∣ses; as well Dioptrical, as Catoptrical.

ibid.

2 A COROLLARIE. Hinting the Causes, why an Elliptical Concave reflects the incident rays, in a more Acute angle, than a Parabolical: and a Parabolical than a Sphe∣rical.

170

3 A CONSECTARY. Why a Plane Perspicil exhibits an object in genuine Dimen∣sions; but a Convex, in Amplified, and a Concave in minorated.

171

SECT. IV.

ARTIC.

1 A Recapitulation of the principal Argu∣ments precedent: and summary of the subsequent.

173

2 The Eye Anatomized: and the proper use of each Part thereof, either absolutely Neces∣sary, or onely Advantagious to Vision concisely demonstrated. viz. 1 The Diaphanity of the Horny Membrane, and the three Humors, A∣queous, Chrystalline, and Vitreous. 2 The Convexity of all its parts except the Amphi∣blestroides. 3 The Uvea Tunica, and Iris. 4▪ The Pupilla. 5 The Blackness of the in∣side of the Uvea Tunica. 6 The Tunica A∣rachnoides. 7 The Ciliary Filaments there∣of. 8 The Chrystalline. 9 The Retina Tu∣nica. 10 The six Muscles, viz. 1 The Di∣rect, as the Atollent, Depriment, Adducent, Abducent. 2 And Oblique, as the 2 Cir∣cumactors, or Lovers Muscles.

173, to 177

3 Why the Situation of an object is perceived by the sight.

177

4 The Reason of the eversion of the Image, in the Amphiblestroides.

178

5 The same illustrate by an Experiment.

ibid.

6 Why the Motion and Quiet of objects are dis∣cerned by the sight.

ibid.

7 Why Catoptrical Images imitate the motions of their Antitipes or Originals.

ibid.

8 Why the right side of a Catoptrical Image respects the Left of its Exemplar. And why two Catoptrick Glasses, confrontingly posited, cause a Restitution of the parts of the Image to the natural Form.

180