Newcomb, Simon, 1835-1909, Holden, Edward Singleton, 1846-1914, joint author · New York, H. Holt · leaf 105
nt about the axis until the middle wireof the reticle seen directly exactly coincides with the image ofthis wire seen by reflection from the surface of the quicksilver.When this is the case, the telescope is vertical, as can be easilyseen, and the nadir reading may be found from the circles.The…
Astronomy
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