1902 Encyclopedia > Geography > Board of Longitude. Nautical Almanac. Sextant.

Geography
(Part 31)



Board of Longitude. Nautical Almanac. Sextant.

In the 18th century, to a far greater extent than had ever been the case before, geography began to be cultivated for its own sake, and expeditions were fitted out with the objects of discovery and of acquiring knowledge. The same objects also generally formed part of those enterprises which were avowedly undertaken for conquest, in the search of wealth, or from motives of religious zeal.

The improvement of scientific apparatus naturally went hand in hand with the progress of discovery. The great desideratum was the means of finding the longitude; and it was the creation of a commission for the discovery of longitude in 1713 which, so far as England is concerned, gave the greatest stimulus to inventions connected with geographical research. To the Board of Longitude is due the conception of the Nautical Almanac, and the establishment of a surveying branch of the naval service. The Nautical Almanac first appeared in 1767, under the auspices of Dr Maskelyne, the astronomer-royal, who, by furnishing tables of lunar distances, supplied another means of finding the longitude. The invention by Hadley, in 1731, of the quadrant for use at sea, which entirely superseded the astrolabe and cross-staff, was a still greater improvement; and it was soon followed by better instruments on the same principle -- the sextants of Dolland and Troughton. The work of travelers on land also became more accurate in proportion as instruments and maps were improved. Early explorers by land were content with itineraries and maps which only indicated distances. The introduction of observations by compass bearing was an important improvement; and after the invention of Hadley’s quadrant, these rough route surveys began to be checked and verified by astronomical observations.





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