Newcomb, Simon, 1835-1909, Holden, Edward Singleton, 1846-1914, joint author · New York, H. Holt · leaf 218
itude as well as the form of our planet has to be foundby combining measurements on its surface with astronom-ical observations. Even a measurement on the earthssurface made in the usual way of surveyors would be im-practicable, owing to the intervention of mountains, rivers,forests, and other… … Fig. 67.—a part op the French triangulation near pares. miles apart, are selected as the extremities of a base-line.They must be so chosen that their distance apart can beaccurately measured by rods ; the intervening groundshould therefore be as level and free from obstruction aspossible. One or…
Astronomy
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