Smith, Hamilton Lanphere, 1819-1903. [from old catalog] · Cleveland, M. C. Younglove and company · leaf 31
uring the length of the shadow of a vertical gnomon orstyle, but Ptolemy introduced the use of graduated spheres. Wehave already observed that all circles are divided into 360 degrees,and these subdivided into 60 minutes each. Hence it is evidentthat by means of a graduated circle, angular… … S from the object B. To observe this angle, or inclination* wemay use a small graduated circle thus. Let A C D be a circlegraduated into 360°, having a moveable index turning on itscentre, which index is furnished at each end with a sight-hole.First look with the index towards the object B, and…
Astronomy · Meteorology · Geology · Paleontology
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