Having described in the former papers the appearances observable when pencils of light from small circular apertures are partially intercepted by certain opaque or transparent objects of definite shape and size ; and having shown that whether shadows or illuminated spaces are thus used, they serve to exemplify the magnifying power of short intervals existing between the organ of vision and the object to be examined, inasmuch as they occupy some position in space, and have a certain form, qualities which pertain to them in common with all substances appreciable by the sense of sight, we proceed to notice the phenomena which result when exceedingly narrow linear apertures are substituted for those of a circular form. In conducting these investigations it was not unreasonable to suppose, à priori, that if the size, the quality, and the position of the object to be examined, the direction and the intensity of the light which was used, the sensitiveness and immediate response of the pupil of the eye to the minutest variation in the quantity of light impinging on the retina, and the refracting qualities of the transparent portion of the visual organ, were each and all taken into account, so that a nice and delicate adjustment of the eye to the light, and of the light as well as of the size of the objects to the eye could be insured, appearances perhaps beautiful, doubtless uncommon, and certainly interesting to the physiologist might be fairly anticipated. Such anticipations, have been so far realized as to present a strong inducement to prosecute the subject with a legitimate prospect of still greater success.

You do not currently have access to this content.