160 LAPHAM LAPIDARY of the Navigator's islands, where De Langle, the commander of the Astrolabe, and a number of men were killed by the natives, and thence proceeded to Botany Bay. A letter from La Pe>ouse to the French minister of marine, dated Botany Bay, Feb. 7, 1788, announcing his intention of proceeding to the isle of France by the way of Van Diemen's Land, the Friendly isles, and New Guinea, was the last intelligence ever received from the expedition. In 1791 a squadron was despatched under Ad- miral D'Entrecasteaux in search of La Perouse, but failed of finding any trace of him. Du- mont d'Urville while at Hobart Town in 1828 learned that fragments of a shipwrecked vessel and her equipments had been discovered in Yanikoro in the New Hebrides group, and sailing thither with his vessel the Astrolabe, ascertained that many years previous two ships had foundered on a reef off the W. coast of the island, and that such of the crews as had not been drowned or murdered by the savages had sailed from the island in a small vessel built by themselves, and never afterward been heard of. Believing that these weje the ships of La Perouse, he caused a cenotaph to be erected near the locality of the shipwreck. LAPHAM, Increase Allen, an American physicist, bora at Palmyra, N. Y., March 7, 1811. He was engaged as a civil engineer on the Welland canal, in Canada, and afterward on the canal around the falls of the Ohio at Louisville, Ky., where he began the collection of his herbarium, which now contains about 8,000 specimens. From 1833 to 1835 he was secretary of the Ohio board of canal commissioners. In 1836 he removed to Milwaukee, Wis., where he now resides, and where he has held several municipal and other offices. In 1862 he was elected president of the Wisconsin historical society. In 1873 he was appointed state geologist, and in 1874 was engaged in making a thorough geological and topographical survey of Wis- consin. He has been a frequent contributor to scientific periodicals, and was the first to demonstrate from minute personal observa- tions that there is a slight lunar tide in Lake Huron. Among his productions are : " Notice of the Louisville Canal, and of the Geology of the Vicinity" (in Silliman's "Journal," 1827); "Wisconsin: its Geography, Topography, His- tory, Geology, and Mineralogy" (1844; 2d ed., 1855); a "Geological Map of Wisconsin" (1855); and "Antiquities of Wisconsin" (in the "Smithsonian Contributions," vol. vii., 1855). ^ In 1867 he made a valuable report to the legislature of Wisconsin upon the disastrous effects of the destruction of forest trees ; and in 1869 he presented a memorial to congress suggesting that system of weather reports which has since been adopted. LAPIDARY (Lat. lapidarius, a stone cutter, from lapis, a stone), a workman whose trade is the cutting and polishing of small ornamen- tal stones. His apparatus consists almost ex- clusively of wheels or disks for grinding down, slitting, and polishing the faces of minerals. These are of a few inches diameter, made of lead, pewter, brass, or iron, and of various soft alloys, and some used for smoothing the soft- est minerals are of willow or mahogany. The metal wheels are called laps. The term mill is applied to them all, and some are distinguished as slitting mills, others as roughing, smoothing, or polishing mills, of all which there are varie- ties adapted to the different degrees of hard- ness of the minerals. The polishing mill for the softest stones is formed of a coil of list, wound with the edges outward ; it is also some- times made of bristles like a brush, or of wood covered with buff leather. For slitting pur- poses an iron disk is employed of 8 or 9 in. diameter and -gfa of an inch in thickness. The various disks used by the lapidary are adjusted to a vertical spindle, and one of them is set in the table or lapidary's bench, so as to revolve horizontally just above the surface. Its axis extends beneath the table, and is there connect- ed by a belt with a driving wheel attached to another vertical axis, which also passes through the table and terminates above in a winch Lapidary's Table. or crank. This is turned with the left hand while the stone is guided upon the mill with the right. The mills are fed with moistened diamond powder or emery and water ; and as the hard powder imbeds itself in the soft metal, this becomes merely the medium for holding the abrading material, and the softer substance apparently grinds and cuts the harder objects that are applied to it. A raised edge around the table prevents the dispersion of the diamond powder or emery. Close to the mill is a round iron rest set in the table, which can be turned nearer to or further from the disk. This is for supporting the arm of the workman in holding the stone to the wheel ; or, when its upright extremity is capped with a wooden socket, which is perforated with a number of holes, it serves to retain at any desired angle a stick upon the end of which is cemented the stone to be ground in facets. By this contrivance the exact inclination required is given to the faces of ornamental stones. Diamond powder for the mills is prepared by grinding the waste particles in steel mortars till they lose their sparkling appearance. It is applied mixed with olive or sperm oil. The slitting mill is
