The utilization of the borate of lime found in theae deposita haa been but little developed. When found pure, or nearly so, it is best ahipped in a raw state, as the materials necessary for ita conversion into borax, or for the extraction of its boracic acid, cannot be got in /oco at a reasonable cost. Nevertheless an attempt waa made to manufacture boracic acid from the mineral, in the following way. The borate is evaporated with sulphuric acid in leaden pans to the consistence of a thick paste, then run out and allowed to cool, by which it hardens. The mass is now placed in cast-iron cylinders heated to redness, while a current of steam passes through. The boracic acid is volatilized with the ateam, and condensed in chambers lined with lead. To remove the sulphuric acid, the vapours are passed through a layer of coke arranged in the upper part of the cylinders, which reduces the sulphuric acid to sulphurous. No fault was found with the procesa ; but the cost of material was excessive, and left no profit. Should the discovery of native sulphur or pyrites in the neighbourhood permit the manufacture of aulphuric acid on the spot, operations might be profitably renewed. A sample taken from 14 tons of borate of lime from this district yielded :— Boracic acid .. 36-24 per cent. Sulphate of soda 2-70 per cent.
Lime 11-10 „ Sesquioxide of iron and alumina 2 25 „ Chlorides of sodium and Water .. 29-35 „ potassium .. 6-25 „ Insoluble residue 12-15 „Fourteen miles north-west of this valley, in the same county, is a second borax field of several hundred acrea. Native borax, in large white monoclinic crystala, is found in the mud near the aurface of a marsh, which in rainy weather is covered with water. The layer of borax (with other boratea in kss proportions) is from 6 in. to 1 ft. in depth.
In Churchill county, are several extensive borate beds, the principal one being over 1000 acres in extent and covered with a deposit of borates of lime and soda which, though not heavy, can be gathered at little cost. Works have been put up to manufacture a tou of borax per diem. Smaller deposits are found throughout the neighbourhood. In the same county, is a lake about If mile in circumference, whoze water is aupersaturated with salts, principally borax. The basin of the lake is symmetrically oval, and lies 150 ft. below the level of the plain. It is probably an extinct crater ; it possesses neither outlet uor inlet, and ia fed entirely by subterranean springs. By pumping out the water and evaporating it, the crude borates might be extracted.
The neighbouring State of' California contains saline lakes reaching to the southern boundary line of the 'United States. Of these, perhaps the best known is the great Borax Lake in the Slate Range, about 400 miles aouth of San Franoisco, and 140 miles north-east of Bakersfield. .This
wonderful formation was first explored by Mr, Arthur Robottom, an energetic and persevering pioneer of commerce, who has searched half the world for borax, and to whom the writer is indebted for much valuable information. The lake is about 15 miles long, and 8 miles across ; it contains immense saline deposits, which are also spread over part of the surrounding valley, forming snow-white incrustations. The appearance of the neighbouring formation is aaid to indicate that the aea waa ouce 60 ft. deep here over a large arca, the ancient beach being plainly visible. Here, too, the borax and other salts seem to have quite distinct habitats. In one portion of the lake, is a reef of carbonate of soda, and uear it, are a number of pyramids of the same product about 4 ft. high and 1 to 2 ft. thick. In the centre, is a ridge of common salt about 5 miles long and 2 rniles wide ; on one margin of the lake, is a bed of borax about 1000 acres iu extent and 3 ft. thick ; and beneath this, a stratum composed of sulphate of soda and borate of aoda, combined to form a solid mass almost as hard as atone, and varying in depth from I to 3 ft. The borate of soda is dirty coloured ; but the salt, lying above the level of the entire deposit, in some places to a thickness of 7 ft., is a3 white as snow. Between the borax bed and the salt ridge, arc a few hundred acres of shallow water, very warm and filled with variegoted crystals, which give the water a particoloured appearance. Fig. 393 well illustrates the disposition of the various salts. The preparation of the borax found on this property is conducted as fellows :—The crude borax is gathered, as free as possible from other salts, in cowhide baskets, which are emptied into carts, and their contents are thus couveyed to the boiling establishment on the shores of the lake, which is the only building within many miles. The mineral is here deposited in vats of boiling water, and kept boiling for five hours, to re move the impurities. The liquor containing the borax in solution is run into large zinc lined coolers, where it crystallizes around the sides, and is then scraped off, packed in bags, and dispatched by mule teams to the nearest st,ation on the Southern Pacific railroad, en route to San Francisco.
Borax has also been found in Death Valley, about 32 miles farther east; but many years will probably elapse before it is utilized, on account of the natural obstacles presented by u waterless, treeless, salt-desert, which has proved the grave of many an emigrant.