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Knight's Mechanical Encyclopedia (ed. Knight), P. (search)
tates. The patents on the subject of paper-making are very numerous. Donkin, however, who devoted so much time and talent to the matter, undoubtedly is entitled to the first rank after Robert, who suggested the idea of making paper in a continuous web. One great difficulty to be obviated was the wetness of the sheet of pulp, which, of course, impaired its tenacity, rendering the manipulations exceedingly difficult. This was, in a large degree, removed by the invention of the dandy by Wilkes, patented in England in 1830. This is a hollow perforated roller, corresponding to the doffer of a carding-machine, over which the paper is caused to pass and is pressed under another roller. The dandy may be so constructed as to exhaust the air from beneath the paper by forming it of an inner and exterior casing of sheet-metal, but in practice this has not been found necessary. The introduction of threads, net, or other woven material into the paper is described in Dickenson's English
Knight's Mechanical Encyclopedia (ed. Knight), W. (search)
lowing interesting facts with regard to the length and high of ocean waves. The mean hight of waves in the Atlantic, driven by a westerly gale, is 18 feet. The greatest recorded hight of a wave in the North Atlantic, from the trough to the crest, is 43 feet. In northwest gales, waves 40 feet in hight have been measured off the Cape of Good Hope, while those off Cape Horn were 32 feet. The velocity of ocean storm-waves in the North Atlantic is about 32 miles an hour, and that recorded by Captain Wilkes for the Pacific Ocean is 26 1/3 miles. In an Atlantic storm the breadth of the waves, measured from crest to crest, is about 600 feet. Some sixty years since a cotton-mill was built on a rocking barge, the machinery to be moved by the force of the waves. See Buckner's patent, May 16, 1873. One patent of March 30, 1869, has a reservoir which is filled by the waves dashing up a curved barrier wall, and the water thus raised beyond its normal hight is caused to drive a mill, and