IVORY IVORY COAST 475 all curiously ornamented with various devices. Their chessmen are unequalled in ingenious workmanship. Ivory is largely used for the handles of knives, and for the keys of piano- fortes and other musical instruments. Its fine texture and smooth surface recommend it for plates for miniatures; and it is used for a great variety of toys, and of mathematical and other instruments. For drawing scales the material is not found so suitable as box or lance wood, for its dimensions change as it absorbs and gives out atmospheric moisture. Billiard balls are liable to the same difficulty ; and as the shrinkage or expansion is greater in the direc- tion of the width of the tusks than in that of their length, the two diameters of the balls are sometimes found to differ materially after they have been made a short time. For this reason they are sometimes roughly shaped and then kept for months in the room in which they are to be used, to acquire the form due to its usual condition as to moisture, when they are finished. Veneers are cut out of the blocks either in straight longitudinal slips, or, by the method first practised by the Russians upon cylindrical blocks of wood, in a spiral sheet, as if this were unrolled from the cylinder sub- mitted to the operation. In the London exhi- bition of 1851 a veneer of this kind was ex- hibited in the United States department, afoot wide and 40 ft. long. In Paris they have been cut in strips of 30 by 150 in. ; and a pianoforte has been entirely covered with this material. Ivory may be made flexible by immersion in a solution of phosphoric acid of specific gravity 1*18 till it becomes translucent. It hardens on exposure to dry air, but assumes its flexibility when placed in hot water. Ivory may be dyed black by soaking it in a solution of nitrate of silver and exposing it to the sunlight, or better by boiling for some time in a decoction of log- wood and then steeping in a solution of red sulphate or red acetate of iron; blue by im- mersion in a solution of sulphate of indigo con- taining potash ; green by dipping the blued ivory in a solution of nitro-muriate of tin, and then in a hot decoction of fustic; yellow by first soaking the ivory in a mordant of nitro- muriate of tin and then in a hot decoction of fustic, or better by steeping it for 24 hours in a solution of neutral chrornate of potash, and then immersing it in a boiling hot so- lution of acetate of lead ; red by first satura- ting ft with the tin mordant, and then immers- ing it in a decoction of Brazil wood or cochi- neal, or a mixture of both. Lac dye will pro- duce a scarlet, and this immersed in a solution of potash will become a cherry red. Violet is produced by mordanting with tin and then treating with a decoction of logwood ; if this is placed a short time in a weak solution of nitro-muriatic acid, it will be changed to a beautiful purple red. Ivory may also be dyed with any of the aniline colors. The imports of ivory, hippopotamus teeth, and narwhal teeth into Great Britain from 1861 to 1871 varied from 9,290 cwt. to 14,599 cwt. a year. Vari- ous substitutes for ivory have been introduced. The best known is that called vegetable ivory, an albuminous substance formed from a milky fluid in the fruit of a species of palm common in Peru and New Granada, the pltytelepJias macrocarpa. It corresponds to the meat of the cocoanut, the fruit of another species of palm. When the nuts are perfectly ripe and dry, the kernels are hard like ivory and very white. It answers very well for many small articles instead of the genuine ivory, but is more liable to tarnish, and does not wear so well when exposed to friction. The French preparation known as Pinson's artificial ivory is a compound of gelatine and alumina. Slabs or tablets of gelatine or glue are immersed for some time in a solution of alumina in acetic or sulphuric acid. The alumina separates and becomes incorporated with the glue, and the plates are then removed, dried, and finally pol- ished. Another preparation of artificial ivory is made by working together bone or ivory dust with an equal portion of albumen or gela- tine to form a paste, and then rolling this into sheets, and hardening them by drying. Sul- phate of barytes finely powdered is used to ad- vantage with one half its quantity of albumen. Tablets thus prepared are used in photography to receive positive pictures. IVORY BLACK, prepared by calcining the shavings and dust of ivory, is ground and levigated on a porphyry slab to produce the beautiful velvety material which is the chief ingredient of the ink used in copperplate printing. (See BONE BLACK.) IVORY, James, a Scottish mathematician, born in Dundee in 1765, died near London, Sept 21, 1842. He completed his professional course in theology at the university of St. Andrews in 1786, after which he was a teacher in the acad- emy of Dundee for three years. He was after- ward for 15 years superintendent of a flax- spinning factory at Douglastown. Meantime he pursued his mathematical studies, and be- came known by remarkable memoirs read be- fore the royal society of Edinburgh. In 1804 he was appointed professor of mathematics in the royal military college, then at Marlow, Buckinghamshire. He retired with a pension in 1819, and from that time prosecuted his fa- vorite studies in the vicinity of London. He was a member of the principal learned societies of England and Germany, and in 1831 received an annual pension of 300. His principal writings are papers in the " Transactions " of the royal societies of Edinburgh and London. Three of these were on the attractions of the spheroids, and contained a process of analysis which was acknowledged by Laplace to be su- perior to his own. IVORY COAST, a part of the coast of Upper Guinea, W. Africa, between the Grain coast and the Gold coast, extending from Cape Pal- mas to the Assinie river. The coast is low, marshy, and unhealthy, but the country back of it rises into table lands of vast extent and
