Page:Encyclopædia Britannica, Ninth Edition, v. 13.djvu/546

522 hundred and fifty men. The price of ivory varies much in different districts, being generally higher on the west than on the east coast ; the transaction is generally one of barter, and the price therefore difficult to estimate. The tusks are sold by weight, and stones arid iron are some times thrust down into the hollow pulp cavity to increase the weight, so that dealers generally feel down the hollow with an iron rod to detect foreign matter. The value of the ivory depends upon the size of the tusks ; those below 6 or 7 Ib weigh b are not worth more than half the price per Ib of really fine tusks. Something depends on the care bestowed upon the tusks, which are sometimes roughly treated, while others are waxed and carefully wrapped up for protection. The African ivory trade is an ancient one, and in medieval times Marco Polo speaks of the traffic in ivory at Zanzibar as being astonishing in its amount. The tusks of the mammoth from northern Siberia are said to furnish almost the whole of the ivory used by Russian ivory workers. They are found in most extra ordinary abundance, and it is said that from the time of Dr Breyne s quaint paper " Behemoth " in the Philo sophical Transactions for 1737 till now there has been no intermission in the supply. They come principally from the neighbourhood of the Lena and other great rivers discharging themselves into the Arctic Ocean, and are abundantly found in the Liakhoff Islands. Mammoth tusks are slenderer, much more curved, and in proportion to the size of the animal much larger than those of recent elephants. In Siberia at different times four mammoths have been found entire, tteir hair, skin, and even all their soft parts having been preserved without change in the ice for countless years. Just as in some few cases all the most perishable soft parts were preserved, so in a vastly greater number the less perishable ivory was kept without change by the low temperature and exclusion of air ; thus when in the summer the ice tears down portions of river banks, or floods break up frozen morasses, the tusks are brought to light. Some are in the most beautiful pre servation, like recent ivory ; others having been exposed before, in previous summers, their organic constituents have partly perished, and they are inclined to become broken up along the lines of iuterglobular space into concentric rings, or may have become so disintegrated that a frag ment may be used like chalk to write with. In England this ivory is not very highly esteemed, being considered too dry and brittle for elaborate work, and to be very liable to turn yellow. Most ivory workers strenu ously deny ever using them, but, though more rarely than in former years, mammoth tusks are occasionally imported. Within the last few years an exceptionally large tusk in splendid condition was offered for sale to the Oxford University Museum at a price of 100, but was not purchased. In 1872 1630 very fine tusks were brought to England ; and in 1873 1140 tusks weighing from 140 to 160ft> each were imported. The best were sold at a very good price, but proved less available, even for such purposes as cutting into knife handles, than was expected, and although smaller importations arrive from time to time they can hardly be considered as a regular article of commerce, and are difficult of sale ; some have been very recently sold at a price so low as ten shillings a cwt. Westendarp personally investigated the Siberian ivory trading districts, and returned with no favourable impres sion. He found that about 14 per cent, of the teeth were good, 17 per cent, could ba made some use of, 54 were quite bad, and 15 wholly useless. The ivory looks better outside than it really is, and, as only about 30 per cent, is usable, it does not pay well for transport. He thought it not worth more than Is. 6d. a pound. The finest quality of ivory from equatorial Africa is closer in the grain, and has less tendency to become yellow by exposure than Indian ivory. When first cut it is semi-transparent and of a warm colour ; in this state it is called " green " ivory, and as it dries it becomes much lighter in colour and more opaque. This is supposed to be the result of the drying out of the " oil " ; but ivory contains less than one-half per cent, of fatty material, and that which dries out is water, not oil. During this drying process the ivory shrinks considerably, so that it is necessary to season it like wood when such things as box lids, which need to fit, are to be made from it. The tusks shrink much more in their width than in their length, which will be readily understood when the many concentric rings of interglobular spaces, containing soft material, which dries up and leaves them empty, are remembered. It is on account of this peculiarity of structure that billiard balls are turned from tusks not greatly exceeding them in diameter, for by the selection of such tusks the ivory on the opposite sides of the ball will correspond in density and in structure, and the shrinkage will be uniform about its centre. They are usually turned roughly into shape, kept for some time in a warm room to shrink, and then turned true. The thin plates cut for piano keys are dried and shrunk at once by being baked for a time in an oven, but after being dried they are still subject to changes in bulk in a moist atmosphere. It is not always possible to judge of the quality of ivory before the tusk is cut up. The exterior, or cemeutum, should be smooth and polished ; it is often of a deep coffee colour in the best tusks, and it should not show any large cracks. But the most profound disorganization of the ivory may exist inside an exterior which promises well, or it may be badly cracked from unequal shrinkage in drying without cracks being noticeable on its exterior. About half of the length of an average sized tusk is implanted ; this will be hollow, and in a young animal the hollow will extend beyond the implanted portion ; the extruded part, recognizable by the deeper colour of its cementum, is solid, and is circular or oval in section. Great care is taken by ivory cutters to cut up the tusk to the greatest advantage, its high price necessitating the strictest economy in its use. Veneers of large size have been cut by a reciprocating saw cutting a spiral shaving round the tusk, one having been thus produced 40 feet in length by 12 inches in width ; but they are not of much practical value, save as an example of what is possible. With age ivory turns yellow, and various receipts are given for restoring its whiteness ; but they mainly depend upon mere removal of the outer surface, and no satisfactory method of bleaching it is known ; it preserves its colour best when exposed to light. Con sidering the high percentage of organic matter which it contains, it is surprisingly durable. In some of the ivories brought by Mr Layard from Nineveh, in which the organic constituent had partially perished, leaving them very friable, its place was supplied by boiling them in a solution of gelatin, a process suggested by Professor Owen as the likeliest means of restoring to them something- like what they had lost during the lapse of time by exposure. It is possible that by some such treatment the perished ivory of the mammoth may be rendered useful for some purposes. The existence of chryselephantine statues of Phidias, and of flat plaques of ivory larger than could be cut from any known tusk, renders it probable that ancient workers possessed some method of bending it; and receipts have come down from the 12th century for softening it so as to alter its form. But these, which depend upon its partial decalcification, have not been found to yield the excellent results claimed for them, and the larger plaques in question present no appearance of having been submitted to any such process. Moreover, Westendarp states that