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 34
Fig. 15.—Davis Back-staff. Fig. 16.—Cross-bow. the observer looked through the lower arc at the horizonline, and at the same time adjusted the sight until he sawthe suns rays through the sight on the upper arc cuttingthe horizon line at the same time. This was certainly amost ingenious device, and…
Cartography · Surveying
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