Treasury of Optics

And because the center of the eye is the same as the center of the surface of the glacialis per 12 n, all these lines will be perpendicular to the surface of the eye, and to the surface of the glacialis, and to all surfaces of the eye equidistant to them; and there will be a pyramid continuous upon all these perpendiculars, containing all these perpendiculars and the air in which the form extends from the entire surface of that viewed object opposite to the eye, according to the directions of the perpendiculars; and the surface of the glacialis will intersect that pyramid; and thus the form of light and color that are in the surface of that viewed object arrives at the part of the surface which the pyramid comprehends.

And to any point of this surface of the glacialis will come the form of the point opposite on the surface of the viewed object, according to the straightness of the perpendicular emerging from that point on the surface of the viewed object toward the surface of the coats of the eye and the surface of the glacialis. It will pass through the transparency of the coats of the eye along the straightness of the perpendicular, and no other form will pass through with that form along the straightness of that perpendicular. And this form will arrive at that part of the glacialis, ordered within it according to the straight lines along which it arrives, which are perpendicular to it and concurring at the center of the eye, just like the ordering of the parts of the surface of the viewed object.

Furthermore, in that disposition, many forms from many points of the viewed surfaces arrive at any point of this part of the surface of the glacialis at the same time. Therefore, many forms from many different colors arrive at this part of the surface of the glacialis that is distinguished by the pyramid. If, therefore, the glacialis senses from the part distinguished by the pyramid the form coming to it from the direction of that pyramid only, and does not sense from that part of its surface any other form except the form coming along that direction, it will sense the form of that object according to its essence, and it will sense it ordered according to its ordering.

And it will also be able to sense in that disposition the forms of other viewed objects, besides that viewed object, by means of the pyramids distinguishing other parts of its surface from that part; and it will be able to sense the form of any of the viewed objects according to its essence, and sense their positions relative to one another according to their essence. And if the glacialis sensed the forms coming to it from refracted directions, it would sense from that same part, which was distinguished from its surface by that pyramid, forms admixed from the forms of the parts of that viewed object and from the forms of many different viewed objects, and they would be admixed from many different colors. And it would sense from any part of its surface, besides that part, a form mixed from the forms of many different objects; and thus it would not sense the form coming along the direction of the pyramid according to its essence, nor any form coming along the perpendicular according to its essence, nor any form coming from refracted directions.

Therefore, it would not sense the form of one viewed object according to its essence, nor would the viewed objects opposite to it be distinguished from one another at the same time; but the eye comprehends viewed objects as distinct, and comprehends the parts of one viewed object ordered according to their essence on the surface of the viewed object, and comprehends many viewed objects simultaneously at the same time. And since vision occurs from the forms coming from viewed objects to the eye per 14 n, the glacialis will sense nothing from the forms of the viewed objects from refracted directions; and thus none of the forms arriving at the surface of the glacialis from the forms of the viewed objects will be ordered on the surface of the glacialis according to their essence; nor will any of the forms of the parts of one viewed object arriving at the surface of the glacialis be ordered on the surface of the glacialis according to their essence on the surface of the viewed object, except for those forms arriving at it according to the straightness of the perpendiculars raised upon the surface of the eye only.

The positions of the refracted forms at the surface of the eye also arrive at the surface of the glacialis inverted, and furthermore the form of one point arrives at a portion of the surface of the glacialis, not at one point. And that is because the form of a point to the right at the eye, when it extends to a point of the surface of the eye, and the line along which the form extends is oblique to the surface of the eye, will be refracted to the left side from the perpendicular which extends from the center of the eye to that point of its surface; and the form which is refracted from the extremity of the perpendicular arrives in this mode at a point to the left of the point of the glacialis surface upon which that perpendicular cuts. And similarly, the form of a point to the left at the eye, which extends to that same point of the surface of the eye and declines upon it, will be refracted to a point to the right of the perpendicular, and to the right of the point of the surface of the glacialis which is upon that perpendicular; for refracted forms do not approach the perpendicular emerging from the place of refraction after refraction, and they do not arrive through the application of the form to the perpendicular, nor do they pass through it after refraction, nor do they precede it; for this is the property of refracted forms. And similarly, the forms of two points that are in the same direction from the eye, which emerge to one point of the surface of the eye and decline upon it in the same direction, arrive at the surface of the glacialis inverted; for the two lines along which the two forms of the points extend intersect at the point of the surface of the eye upon which the two forms concur, and they meet the perpendicular emerging to that point of the surface of the eye upon that point. When, therefore, these two lines are declining from the surface of the eye in the same direction from the perpendicular emerging from the center of the eye to that point, the forms of the two points are refracted to the point opposite to that part. And also because the two lines, along which the two forms extend to one point of the surface of the eye, intersect at that point; reversed in respect to that which is in the viewed object, and in respect also to the perpendicular, and the line which was on the right before its arrival at the surface of the eye from those two lines becomes the left after its passage through the surface of the eye, and the left, the right. And similarly, there will be the position of the two lines along which the two forms from one point of the surface of the eye are refracted: for the two forms which are refracted from one point both approach the perpendicular, and the form which was along the line further from the perpendicular extends...