Elements of theoretical and descriptive astronomy, for the use of colleges and academies (1901)
White, Charles J · New York: J. Wiley & sons · leaf 59
consider the air to be made up ofi series of strata concentric with the earths surface, the ^thick-ness of each stratum being in-definitely small, and the den-sity of each stratum beinggreater than that of the stra-tum next above it. Now, inFig. 20, let the arc BD repre-sent a portion of the… … REFRACTION 53 drawn. As the ray of light passes down through the atmos-phere, it is continually passing from a rarer to a densermedium, so that its path is continually changed, and becomesa curve AL, concave towards the earth, and reaching the earthat some point L. Since the direction of a curve al…
Astronomy
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