Elementary astronomy; a beginner's text-book (1899)
Holden, Edward Singleton, 1846-1914 · New York, H. Holt and company · leaf 265
a crack ina shutter may brighten the whole of a darkened room. 244 ASTRONOMY. The Suns direct rays do not reach an observer on theEarth after the instant of sunset, since the solid body ofthe Earth intercepts them. But the Suns direct raysilluminate the clouds of the upper air, and are… … Fig. 154.—The Phenomena of Twilight. the horizon of A, Bb of B; Cc of C; Dd of D. Let thecircle PQR represent the upper layer of the atmosphere.Between ABCD and PQR the air is filled with suspendedparticles that reflect light. The lowest ray of the Sun,SAM, just grazes the Earth at A; the higher…
Astronomy
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![An illustration from L'optique divisée en trois livres : ou, l'On démontre d'une maniere aisée tout ce qui regarde 1. la propagation & les proprietez de la lumiere. 2. La vision. 3. La figure & la disposition des verres qui servent à la perfefectionner [sic] (1682)](https://img.insideoutlibrary.com/img/200/ia-loptiquedivise00ango-77-8.webp)
