Philosophical instructor, or, Webster's elements of natural philosophy : subdivided into principles and illustrations ; intended for academies, medical schools, and the popular class-room (1824)
Eaton, Amos, 1776-1842, Webster, John, fl. 1804-1824 · Albany : Printed by Websters and Skinners ... · leaf 211
are obscured ; thus, if the shadow passthrough a quarter of the moons diameter, it has threedigits eclipsed. The earth, like all other opake globular bodieswhich receive the suns rays, not only throws a darkconverging or conical shadow behind it, but has like-wise a thin diverging shadow on each of… … total obscuration in the cone m, a, n, which cannotreceive a ray of light from any part of the sun ; anda penumbra or thinner shade will fall on each side,in the angular parts b m a, c n a, increasing in dark-ness towards the sides m a, n a. For the penumbra b m a can only receive a partiallight…
Physics
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