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Knight's Mechanical Encyclopedia (ed. Knight) 5 1 Browse Search
Harper's Encyclopedia of United States History (ed. Benson Lossing) 2 0 Browse Search
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Harper's Encyclopedia of United States History (ed. Benson Lossing), Davidson, George, 1825- (search)
Davidson, George, 1825- Astronomer; born in Nottingham, England, May 9, 1825; came to the United States in 1832; graduated at the Central High School, Philadelphia, in 1845; engaged in geodetic field and astronomical work in the Eastern States in 1845-50, and then went to San Francisco, and became eminent in the coast survey of the Pacific; retiring after fifty years of active service in June, 1895. He then became Professor of Geography in the University of California. Of his numerous publications, The coast pilot of California, Oregon, and Washington; and The coast pilot of Alaska are universally known and esteemed.
o that, when air is admitted in front of the piston in the cylinder, the brakes are at once applied to the wheels. See brake, p. 356. There have been numerous attempts to secure automatic and simultaneous action, throughout the cars of a train, by power derived from a single impulse or operation. Room cannot be spared for their systematic description, but the following patents may be consulted: — Bessemer (English)1841Hodge1860 Hancock (English)1841Dwelley1865 Nasmyth (English)1839Davidson1860 Petit1840Marsh1864 Birch1840Virdin1859 Carr (English)1841Wilcox1856 Walber1852De Bergues1868 Fuller1859Chatelier1868 Sickels1857Lee1868 Cuney1855Ambler1862 Goodale1865Branch1858 Peddle1867McCrone1865 Car-buf′fer. (Railway.) A fender between cars. In the English practice, the ends of the car-frames carry elastic cushions, or buffer-heads with springs. In our practice the spring is usually behind the drawbar. See buffer. Car-bump′er. An elastic arrange
earder, Hjorth, and others. Professor Jacobi of St. Petersburg, in 1838-39, succeeded in propelling a boat upon the Neva at the rate of four miles an hour, by means of a machine on this principle. The boat was 28 feet long, about 7 feet wide, drew about 3 feet water. The battery used consisted of sixty-four pairs of plates, and propelled the boat by paddlewheels. He also applied his engine to working machinery, but without decided success. Page's electro-magnetic engine. In 1842, Davidson constructed an electro-magnetic locomotive-engine which attained a speed of about four miles an hour on the Edinburgh and Glasgow Railway. E-lec′tro-mag-net′ic ma-chine′. See electro-magnetic engine. E-lec′tro-mag-net′ic Reg′u-la-tor. A device for maintaining an even heat in an apartment, a bath, or a furnace. See thermostat. E-lec′tro-mag-net′ic Tel′e-graph. A signaling, writing, printing, or recording apparatus in which the impulses proceed from a magnetic
rface; the apparent angle must therefore be divided by two. Besides the uses of the sextant as specially adapted to the purposes of the astronomer and navigator, it is also used by the surveyor for measuring angles and for filling in the detail of a survey when the theodolite is used for the long lines, and laying out the larger triangles. The box-sextant (which see) is a small instrument specially contrived for this purpose. Sextant. The spirit-level sextant, invented by Mr. George Davidson, of the United States Coast Survey, is designed for observing the altitudes or depressions of celestial and other objects, dispensing with both the natural and artificial horizons. It consists of an observing tube, on top of which is a spiritlevel, the bubble of which is viewed by reflection from a plane mirror just below it, forming an angle of 45° with the axis of the instrument. As the level is too near the eye for distant vision, a convex lens is inserted in the tube between the