Maps and map-making; three lectures delivered under the auspices of the Royal geographical society (1910)
Reeves, Edward Ayearst, 1862-1945, Royal Geographical Society (Great Britain) · London, The Royal geographical society · leaf 37
ea under favourable conditions. ,; We now come to an epoch-making change inthe construction of instru-ments for navigation, andthat is the introductionof the reflecting mirrorsin the quadrant. Theoriginal suggestion of aninstrument for measuringangles between two objectsby reflection, so that… … Fig. 19.—Newtons Reflecting Octant. INSTRUMENTS 19 could be made on this principle. Although the honourof doing this is generally thought to belong to John Hadley,the fact is, Sir Isaac Newton, in 1700, in a letter to Halley,the Astronomer Royal, described most minutely an instru-
Cartography · Surveying
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