The second most important borax deposit of California is in Borax Lake (or Lake Kaysa, as it is called by the Indians), a pond covering 200-400 acres according to the season of the year, situated a short distance east of, and separated by a Cretaceous ridge from, the Clear Lake, about 110 miles north of San Francisco. According to John Arthur Phillips, Esq., F.G.S., who made a careful ex amination of this property, the borax occurs chiefly in the form of crystals of various sizes imbedded in the mud of the bottOm of the lake, which is found to be most productive to a depth of 3 to 3i ft., though the earth brought up by a boring rod, put down near the centre to a depth of 60 ft., is said to have afforded proportions of the salt throughout. The crystals are most abundant near the centre, and over about one-third of the surface; but they are also met with in the muddy deposit of other portions of the basin, some—in the richest part—being over 1 lb. in weight. The largest crystals are generally imbedded in a stiff blue clay, at a depth of 3 to 4 ft. ; a short distance above them, is a nearly pure stratum of smaller ones, 2i to 3 in. in thickness, in addition to which, crystals of various dimensions are found disseminated through the muddy bottom. Besides the borax thus existing in a crystalline form, the mud itself is highly charged, and when dried, yields (including the enclosed crystals) 17.75 to 18.86 per cent. of borax. These figures refer to the portions of ground now being worked ; but the unworked portions also, though less productive, contain a large amount of borax. It has further been ascertained, by making pits on the lake shore, that clay containing a certain proportion of borax exists in the low ground, at a distance from the water's edge. The borax is at present manufactured extensively froin the native crude crystals, while the mud in which they are found is returned to the lake, after the mechanical separation of the crystals by washing, the mud being raised by sheet-iron cofferdams and a small dredging machine. It is evident that in this way only a portion of the borax is recovered. As to the extent of the deposit and its capabilities of production, Mr. Phillips furnishes the following data. The total extent of the muddy deposit consists of more than 300 acres ; but supposing only 100 acres to be rich enough to pay for working, and that the depth is only 3i ft., there will be 565,000 cub. yds., or at least 565,000 tons of wet mud, or say (allowing 60 per cent. of water) 226,000 tons of dry mud, contain ing, according to mean analyses, 18.29 per cent. of borax ; but gmnting that only 12 per cent. is got out in practice, there will be a yield of 27,120 tons of crystallized borax, without considering some (estimated) 6000 tons existing in solution in the waters. But even this does not include the total productive capability, for it is evident that borax is constantly being formed, through the decumposition of the carbonate of soda abundantly contained in the waters of the lake, by boracic acid emitted from the sources benes,th its bed, since large volumes of carbonic acid gas constantly escape from the surface. Another authority believes that the deposit would renew itself every two or three years. The borax, after boiling and crystallization, is packed in boxes of 111 lb. weight for transport to San Francisco. Mr. Phillips estimated the production here at 2500 lb. to 2800 lb. per diem, at a cost of about 18/. a ton.
There is every probability that the dry lake beds farther towards the south-eastern extremity of the State will also be found to contain borax. Among the minor occurrences of boraeic com pounds in North America, may be mentioned Howlite, near Lake Superior and in Nova Scotia ; Ulexite, in Nova Scotia and Nevada ; oryptomorphite, in Nevada and Oregon ; borax, in Canada. Boracic acid exista as a constituent of mineral waters in California, Colorado, Nevada, Wyoming, Maine, and Nova Scotia. Very appreciable quantities of borates, apparently in the form of borate of soda, and perhaps of lime also, are found in the waters of the Pacific, from San Diego to the Straits of Fuca, becoming hardly perceptible beyond Oregon, and reaching a maximum ndar San Diego. Their presence cannot be traced seawards beyond the submarine ridge running parallel
with the coast. Dr. Veatch considers their source as undoubtedly volcanic, and looks for the seat of the volcanic action in this submerged mountain rdnge.
5. America (South).—An important source of boracic minerals has been found in the salinas of South America, notably those on the Pacific face of the Cordillera of the Andes, in Peru, Bolivia, and Chili. These salinas are later in age than the Tertiary deposits, and appear at intervals scattered over the whole of that portion of the western coast where no rain falls, stretching more than 550 miles north and south, but exhibiting the greatest development between latitudes 19° and 25° south. They are generally superficial; but occa,ionally reach to some slight depth below the crust, and may then be entirely covered over with diluvial detritus, always, however, giving signs of their existence by a saline efflorescence on the surface of the ground, which often covers vast plains as a white crystalline incrustation. The salts forming these salinu present combinations of the follow ing minerals, in a more or less pure state :—Common salt, Epsom-salt, glauber-salt, thenordite, glauberite, soda-alum, mag,nesia-alum, gypsum, anhydrite, chloride of calcium, iodide and bromide of sodium, carbonate and nitrate of soda, and, in some places, borate of lime and of soda. The boracic acid compounds are ascribed to volcanic causes, while all the other mineral substances present are such as would be left on evaporating sea-water, or by tbe mutual reactions of the saline ruatter (thus left by evaporation) on the organic matters and constituents of the adjacent rocks. In the presence of abundant evidence of the recent elevation of the c,oast, and tho fa,ct that no rain falls in these regions, it seems very reasonable to attribute the origin of these salinas to lagoons of salt water, cut off by the rhing of the laud.
The salinas are met with at three very different altitudes above the sea, viz. :—about 2500 ft. to 3500 ft. ; 7000 ft. to 8000 ft.; and 12,500 ft. The first include the important beds of nitrate of soda, runniug from lat. 19° southwards into the northern part of the Desert of Atacama, showing themselves, according to the configuration of the country, at distances varying from 10 to 40 miles inland. The boracic acid compounds met with are believed, by Professor Forbes, to be due to volcanic exh .lations ; and the borate of lime, occurring in large quantities, appears to be indirectly produced by the condensed vapours of volcanic fumaroli, many of which are still in full activity in tbe district. The borate of lime is found only in the more elevated part of the salina, on its eastern side, where the rising ground begins to form the western slope of the adjacent cordillera. As volcanic action is developed on a grand scale in tbis range, such fumaroli forming lateral vents are very common, and it is to be expected that the waters coming down the slopes carry with them in solution the boracic acid contained in the condensed vapours of the fumaroti, which, coming into contact with the lime of the decomposed rocks of the plains below, would readily combine to form the nodules of borate of lime here found. Moreover, the borate deposits recede from the coast as they advance south, following the eastward treud of the volcanic formation. The second series of salinas are developed on a grand scale in the northern part of the Desert of Atacama, the principal oue with a length of more than 100 miles, and a width of 20 to 30 miles, and a smaller one farther south, about 30 miles long and 12 miles wide. The third and highest series occur in a numher of swamps, commencing at Laguna Blanca, and more or less developed all the way to Oruro, and thence past Sora-Sora far to the south.