Treasury of Optics

culari, and after the intersection upon the line that is also further from the perpendicular, but of lesser distance than the line upon which it was. And the form that was upon the line closer to the perpendicular extends also after the intersection upon the line also closer to the perpendicular, but of greater proximity than the line upon which it was. And likewise for all forms that extend from one point. And when this has been tested by subtle experimentation, it will be found as we have stated. And we shall show the way by which this will be tested by true experimentation in our discourse on refraction, and then all things dependent upon refraction will be uncovered. And we shall not use in that place for demonstration those things we used in this treatise. Therefore, two points inclining to one side from the viewed object, when their forms extend to one point of the surface of the eye, will intersect upon two lines whose position at the eye, with respect to the viewed object, will be contrary to the position of the two primary lines upon which the two forms were extending to the surface of the eye. Therefore, the position of the two points on the surface of the glacialis crystalline lens to which the two forms arrive will be contrary to the position of the two points from which the two forms come. Therefore, all forms that are refracted from one point on the surface of the eye arrive at the surface of the glacialis inverted. And again, the form of any point opposite to the eye comes to the entire surface of the eye; therefore, it will be refracted from the entire surface of the eye. And the form that is refracted from the entire surface of the eye is refracted to a part of some quantity of the surface of the glacialis, not to a single point. For if the forms of refraction were to concur after refraction upon one point, they would intersect the perpendiculars at whose extremities they were refracted, or they would pass through them, or the form would exit the surface in which it was being refracted. But no refracted form meets the perpendicular at whose extremity it was refracted after refraction, nor does it pass through it, nor does it exit the surface in which it was refracted. And all these things are manifested through experimentation. Therefore, the form of one point of a viewed object that arrives at the surface of the glacialis after refraction will not be in one point, but in a part of some quantity of the surface of the glacialis. And the position of the forms of diverse things, or of diverse points of the surface of the viewed object, that arrive at the surface of the glacialis before refraction, will not be among themselves as their position is according to their existence on the surfaces of the viewed objects, but contrary. Therefore, none of the refracted forms of viewed objects arriving at the surface of the glacialis is according to its existence on the surfaces of the viewed objects. And it has already been declared original: "iām declaratũ est [18 n]" that forms coming along perpendiculars are ordered on the surface of the glacialis according to their existence, since they extend straight from the surfaces of the viewed objects to the surface of the glacialis. Therefore, none of the forms of viewed objects coming to the surface of the glacialis is ordered on the surface of the glacialis according to its existence as it has on the surfaces of the viewed objects, except for the forms extended along the directions of the perpendiculars only. If, therefore, the sense of sight of viewed objects comes from forms arriving at it from the surfaces of the viewed objects, the eye will comprehend nothing from the forms of viewed objects arriving at it, except from the directions whose extremities concur at the center of the eye alone. This is because the eye comprehends nothing from the forms of viewed objects unless it is ordered according to its existence on the surfaces of the viewed objects.

20. The eye and the crystalline sphere have the same center. 7 p 3. The same 12 n.

And again, if the center of the eye is not the center of the surface of the glacialis, the straight lines that exit from the center of the surface of the eye and extend into the hole of the uvea the iris/pupil structure and arrive at the viewed objects will not be perpendicular to the surface of the glacialis, but inclining upon it. Nor will their position upon the surface of the glacialis be a similar position, except for one line only, namely, the one that passes through the two centers. Therefore, the glacialis cannot sense the forms coming from the surfaces of the viewed objects except from the directions of these lines only, namely, those which are perpendicular to the surface of the eye, which is the surface of the cornea. This is because the forms that are upon these perpendiculars are the only ones ordered on the surface of the glacialis according to their order on the surfaces of the viewed objects. If, therefore, the glacialis comprehends viewed objects from forms arriving at it, and it does not comprehend a form except from the directions of these lines, and these lines are not perpendicular to its surface, then it will comprehend forms from directions whose positions on its surface are diverse positions, inclining upon its surface, and it will comprehend all refracted forms from directions of diverse positions inclining upon its surface. And if it comprehends all refracted forms from directions of diverse positions, nothing will be distinguished by it from the viewed objects, for the reason that was declared above. And since it is not possible that it comprehends refracted forms from directions of diverse positions, it is not possible that it comprehends the forms of viewed objects from the directions of lines that are perpendicular to the surface of the eye, except when the lines are perpendicular to its surface, and their positions on the surface are similar. And these lines will not be perpendicular to its surface unless the center of its surface and the center of the surface of the eye are the same point. If, therefore, the sense of sight of viewed objects is from the forms arriving at it from the colors and lights of the viewed objects, and this distinctly, it is necessary that the center of the surface of the eye and the center of the surface of the glacialis be one common point. And the eye comprehends nothing from the forms of viewed objects except from the directions of straight lines whose extremities concur at one and the same point only. And it is not impossible that the two centers be the same, since it has been declared original: "[6.8 n]" that the two centers are from the posterior center of the uvea and pass upon one straight line through all centers. And since it is not impossible that the two centers be the same, and that the straight lines that exit from the centers be perpendicular to the two surfaces, namely the surface of the glacialis and the surface of the eye, it is also not impossible that the comprehension of the eye of viewed objects be from forms arriving at it, of light and color that are on the surface of the viewed objects, since the comprehension of these forms is from the directions of the perpendiculars alone. And that is such that the nature of the eye receives those things that come to it from the forms of the viewed objects, and also that the nature of the eye be furthermore appropriated so that it does not receive those things that come to it from the forms except from their proper directions, not from all directions.