A treatise on levelling, topography, and higher surveying (1876)
Gillespie, W. M. (William Mitchell), 1816-1868, Staley, Cady, b. 1840, ed · New York, D. Appleton and company · leaf 135
he incident ray now makes an angle with this mirror n°greater than before; it will therefore pass off, making an an-gle with the mirror n° greater than before. But the mirroritself now makes an angle of n° with its former direction;therefore, the ray will pass off at an angle of a° + 2n° withthe… … If, now, an eye, placed at E, sees an object in the secondmirror, in the direction E H, which has been reflected fromtwo mirrors, then the line E H makes an angle with the truedirection of the line equal to twice the angle which the mir- THE INSTRUMENTS. 117 rors make with one another. If the eye…
Surveying
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