Recreations in astronomy : with directions for practical experiments and telescopic work (1879)
Warren, Henry White, 1831-1912 · New York : Harper & Brothers · leaf 55
r, say an inch in surface, and putting under it three little pellets of wax. putty, or clay, <et it on the wrist, with one of the pellets on the pulse. Hold the mirror steadily in the beam of light, and the frequency ami prominence of each pulse-beal will be indicated by the • ,t of light on the… … to rise into sight. When light passesfrom a medium of one density to amedium of another, its direction ischanged. Thus a stick in water seemsbent. Ships below the horizon aresometimes seen above, because of thedifferent density of the layers of air. Thus light coming from the interstellar spaces,…
Astronomy
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