Note 30 — CHAP. III. A DESCRIPTION OF THE MOST APPROVED MICROSCOPES, AND THE METHOD OF USING THEM.

This effect by the lanthorn and lamp is subject to much limitation in the field of view, or circle of light thrown upon the screen. A circle of not more than from 12 to about 15 inches can ever be obtained with any tolerable strength of light, to shew the most transparent sort of objects that can be found, such as the scale of a sole fish, a fly’s wing, &c. The great difference between the light of the sun and a lamp is a natural obstacle to great performances in this way, and renders them far short of the effects of the solar microscope. The exhibition, however, is considerable, and much deserving of the notice of any observer disposed to this sort of apparatus. Probably, subsequent experiments may yet produce more light on this instrument. The best sort of apparatus for this purpose hitherto made, I shall describe in a following section. Edit.