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 179
n of the sun may be thrown in any desired direction.They have been observed on at a distance of 80 or 90 miles,when the outlines of the mountains on which they were placedwere invisible. A man, called a heliotroper, is stationed 1 To determine at astation A,whether its signal can be seen from B,… … THE FIELD-WORK. 159 at the instrument. He directs the telescope toward the sta-tion at which the transit is placed for observation, and keepsthe mirror turned so as to reflect the sun in a direction parallelto the axis of the instrument. This he accomplishes by caus-ing the reflection to pass…
Surveying
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