Publisher's Synopsis
Excerpt from Observations on Vision
Amusing myself with these changes of the pupil, as amat ter of curiosity, by presenting to the eye different objects at different distances, I soon perceived that its contraction and dilatation were irregular and more limited than had been supposed: i. E. That approaching the object nearer the eye, within a certain distance, the pupil not only ceased to con tract, but becatne again dilated; and that beyond afew yards distance, it also ceased to dilate: these circumstances im mediately occurred as objections to the above explanation for were it from the contraction and dilatation of the iris alone that we see objects at different distances, I naturally concluded it should operate regularly to produce its effects; but if to View an object at a few yards distance it be enlarg ed to the utmost extent, surely'it must of itself be insufficient to view one at the distance of several miles; for example, the heavenly bodies.
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