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 33
pon which were made to slide one or more crosspieces. The staff was graduated, and the cross pieces could be moved along it until,looking through thesight near the eye,they would be seento cover the two ob-jects between whichthe angle was to bemeasured, which wasthen read off the gra-duation. In… … Fig. 14.—Cross-staff. INSTRUMENTS 15 for observing the sun when the eye was protected by somekind of shield, and it was principally for this reason that itwas later on superseded by the Back-staff (Fig. 15). The Back-staff was invented by Captain John Davis, thefamous old Arctic navigator, about…
Cartography · Surveying
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