The importations of Asiutic borax now bear but a small proportion to our total consumption. No doubt new sourcea will be opened up as the country becomes explored and new trade routes are made, and the production of already known sources could doubtless be much increased by scientific treatment ; but there remain the terrible passes of the Himalayas to be erossed, by which the trade muat for a long time be heavily handicappe,d in the competition with other countries.
Among other Asiatic countriea, Ceylon and China are said to produce borax; but the amount is so small that it never finds its way to foreign markets. Future explorations may reveal larger deposits. Turning to Turkey, we find that in Asia Minor have been discovered important deposits of boracite (borate of mag,nesia). This valuable mineral occura in nodules of 3 lb. and upwards, regularly disseminated through beds of gypaum. It has already become an artiele of export, though the iudustry has hardly had time to develop itself. Boracite is one of the richest boracie minerals, and it is hoped that it may be found in suffieient abundanee to become the subject of systematic mining.
3. Afrka.—Africa is not known to possess any depoaits of borax ; but it is possible that the rhodizite, or " African tinealzite," as it has been called, a kind of boraeite found on the west coast, may be discovered in such quantity as to repay working expenses.
4. America (North).—It is from the New World that the greater part of our supply of borax is at present drawn. The principal occurrence of boracie minerals in North America is on the Pacific slope, notably about the Sierra Nevada, and the Slate Range of California. In the State of Nevada, con siderable beds have been worked. The Columbus diatriet, Esmeralda County, contains, it is said, some 20,000 acres of rich borax land, besides some thousanda of acres of lesa rich deposits, which will only pay for collection during the driest seasons. The Columbus Valley, where the deposit ia richest, is about 10 miles in length and 7 miles in width, and entirely destitute of all but saline vegetation, being covered principally with light briny inerustationa, though near the borders of the valley are wide stretches of drifting sands. Water is usually found at a depth of 2 ft., and, on the west side of the valley, ia fit for drinking. Borates of lime are found in small quantities in all parts of the valley, but chiefly at the northern extremity, where the wash from the hills ia collected. Here they form a large bed, covered with a coating of salt. The accumulation varies in thickness with the moisture of the ground., inereasing in warm, d.ry weather, and decreaaing under the influence of cold and wet. The whole surface is elevated aeveral inches in the early part of the summer, and augments continually till the arrival of the first autumn rains. Its rise and fall are likened to the movements of a huge pan of dough. Each alternation of weather adds to the thieknesa of the actual deposit, the process being evidently analogou.s to that already recorded of the Ladak beds. Where, in 1869, pieces of mineral only as large as walnuts were taken out of the prospecting holes, there is now said to be found a deposit varying from lumpa as large as potatoes to a solid stratum 2 ft. thick. A layer of salt a few inches thick underlies the borate bed, and is again underlaid by a band of aulphate of soda, beneath which, beds of clay and sand alternate to unknown depths. Borate of soda is also found in the marsh. The deposit lies at an elevation of about 3500 ft. above
the sea, and is surrounded by mountains of old volcanic formation, principally obsidian, basalt, end trachyte. Saline effiorescenees containing borates are common throughout, and doubtless form the some° of the deposits in the basin, whieh receivea the wash and pereolation from the hills. The borate of lime is probably formed in situ by a proeesa of double decomposition. It usually occurs in long, brilliant filaments in nodules; but also in amorphous masses mixed with sand, aud salta of soda. The borate of soda is said to be found on the surface a,s a crystalline efflorescence, resembling very fine snow, but yellowish white in colour ; it is sometimes a foot thick.
Tlae company working here have hitherto used only the borate of soda. This is raked together in heaps, with ehovels of thin steel, made sharp at the edge for cutting off the saline herbs which gmw abundantly on the apot. Care is tsken to avoid the patehes of salt, and sulphate of soda. The first is easily recognized by its taste, but the second is much more difficult of distinction by that means ; these salts, however, form crystals quite distinct in eharacter from borax. The gathered borax is transported in carts, and spread on a large platform placed above wooden vats of some 385 bushels capacity. These are filled with water, which is heated to boiling by an injection of steam. The crude borax is added by degrees, till the density of the mass reaches 1.241 sp. gr. —a concentration which would be much too great if borax alone were introduced ; but the sulphate of soda, and salt, as well as the mud, and borate of lime in suspension, help to increa.se the density. When the boiling solution has reached this degree of strength, it is left; the herbs floating the surface are removed with a skimmer, and the liquor is run into crystallizing pans, by means of indiarubber tubing. The removal is performed with great care, ao as t,o keep the liquid as clear as possible. The crystallizing tanks are largo vats about 10 ft. long, 3 ft. 4 in. wide, and 6 ft. 8 in. deep. There the liquid cools alowly down to about 25° (77° F.), occupying aix to ten daya, according to the weather. When the temperature sinks below 28° (82° F.), the cryatallization is carefully watched, that the mother-liquor may be run off before the aulphate of soda is deposited ; no fear need be entertained of the precipitation of the salt preaeut, aa it requires a much lower temperature for crystallization. The point 77° F. being reached, a cork is withdrawn from the bottom of the vat, to allow the mother-liquor to eae,ape. Mud, mixed with numerous crystals of borax, flowa out at the same time ; these crystals are washed with the mother-liquor from a subsequent vat, and preserved for refining. This is a delicate operation, and soon givea the workmen rheumatism, from atanding in the mud. A crust of borax, sometimes 6 in. thick, forma at the bottom of the vat, and ia removed by picks. The presence of borate of lime makea the crystals adhere atrongly to the aides of the vat. The bOrax is placed to dry on platforms, and, at the end of four or five days, is put into old coffee-sacka holding lf cwt. The raw product yields about 30 per cent. of borax, and the cost of manufacture at these works is placed at 8/. per ton. The cost of transport to rail ia about 10/. per ton, and thence to San Francisco about 3/. 10s. more. There it aells at about ls. 9d. per lb. Matters containiog leas than 50 per cent. of borax cannot be worked profitably here.