Qu. Whether per se proportion of visible magnitudes be perceivable by sight? This is put on account of distinctness and confusedness, the act of perception seeming to be [pg 074] as great in viewing any point of the visual orb distinctly, as in viewing the whole confusedly.
Mem. To correct my language & make it as philosophically nice as possible—to avoid giving handle.
If men could without straining alter the convexity of their crystallines, they might magnify or diminish the apparent diameters of objects, the same optic angle remaining.
The bigness in one sense of the pictures in the fund is not determin'd; for the nearer a man views them, the images of them (as well as other objects) will take up the greater room in the fund of his eye.
Mem. Introduction to contain the design of the whole, the nature and manner of demonstrating, &c.
Two sorts of bigness accurately to be distinguished, they being perfectly and toto cælo different—the one the proportion that any one appearance has to the sum of appearances perceived at the same time wth it, wch is proportional to angles, or, if a surface, to segments of sphærical surfaces;—the other is tangible bigness.
Qu. wt would happen if the sphæræ of the retina were enlarged or diminish'd?
We think by the meer act of vision we perceive distance from us, yet we do not; also that we perceive solids, yet we do not; also the inequality of things seen under the same angle, yet we do not.
Why may I not add, We think we see extension by meer vision? Yet we do not.
Extension seems to be perceived by the eye, as thought by the ear.