Wentworth, G. A. (George Albert), 1835-1906 · Boston, Ginn & company · leaf 215
he vernier marked 9 coincideswith a line of the limb. Hence, the reading is 32° 9. When the index moves from the zero line of the limb in adirection opposite to that in which run the numbers of thelimb, the number of minutes obtained as above must be sub-tracted from 30 to obtain the minutes… … 20 25 30 25 20 ,,. 5 zero V b 10 1 1 1 1 ♦
Trigonometry · Surveying · Navigation
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