the island, a distance of between six and seven hundred feet. It is of excellent quality, containing a high percentage of binoxide, and is remarkably free from iron, lime, or other materials for which chlorine gas has an affinity. The ore is accompanied by a black, flinty ganguestone, which is likely to be mistaken by the inexperienced eye for it, but which is of very much lower specific gravity, and is therefore easily sorted. Over two hundred tons, containing by analysis from carefully averaged samples over seventy per cent. of binoxide, have been shipped from this locality to New York, and sold for less than enough to pay freight and commissions. Although enormous amounts of bleaching powder, or chloride of lime, are consumed, nearly the whole of it is imported from England, its extensive manufacture having been but recently commenced in the United States. The demand for it in New York city is therefore exceedingly limited. The price of oxide of manganese in the English market during the past few years has ranged so low-extensive deposits having been discovered in Spain, from whence that market is supplied, as to preclude the probability of the pecuniary success of its being mined here to any considerable extent. The actual cost of its delivery at Liverpool will probably exceed its value in that market, or at any rate equal it.

The rapid introduction of the chlorination process in California, for the extraction of fine gold from the auriferous sulphurets, will create a limited home demand for the article. As an agent for generating chlorine for bleaching purposes, the paper manufacturing companies would probably find a considerable saving to result from its use. In the method at present adopted by them-the employment of bleaching powder-the lime merely serves as a vehicle of transportation for the chlorine, which has already been generated by means of oxide of manganese. Other deposits of pyrolusite occur in the metamorphic cretaceous rocks, but they are apparently of very limited extent, and not likely to prove valuable.

NORTH OF THE BAY OF SAN FRANCISCO.

The valleys included between the Coast Ranges north of the Bay of San Francisco, though numerous, are generally smaller and narrower than those to the south of it. The mountain ranges are but a continuation of those already described, and are made up of rocks of the same general character-silicious and jaspery rocks predominating, and serpentine occurring in enormous masses, though volcanic rocks and materials play a much more important part than in the ranges south of Suisun bay.

Tamalpais, a conspicuous mountain on the north side of the depression which forms the Golden Gate, rises quite abruptly to an elevation of 2,597 feet. Its summits, of which there are three, consist of metamorphic sandstone, in some places marked by quartz veins having a banded structure. Heavy masses of serpentine occur on its western and northern slope. A ridge of this material, nearly 2,000 feet high, extends several miles to the northwest. A short distance west of the town of San Rafael, is a mass of trachyte extending some distance east and west.

Three quarters of a mile southwest of Petaluma, a belt or dyke of compact basalt occurs. In places it has a columnar structure, and is about two hundred yards in width. It has been used to some extent as a building material at Petaluma; its hardness, and the difficulty of obtaining stones of large size, render it undesirable for that purpose; but it makes a durable material for ballasting roads, or a concrete for submarine construction, this being the most accessible point to the city of San Francisco, where such material can be obtained in large quantities. Eruptive rocks also occur at points between Petaluma and San Rafael, but not as favorably situated for shipment as the basalt near Rudesill's Landing.

Between Tomales bay and Petaluma is a line of marked depression. In the vicinity of Tomales, the miocene tertiary, undisturbed and resting conformably upon the cretaceous, is represented. The belt of granite, which occurs on the west side of the peninsula of San Francisco, appears at the extremity of Tomales point; at Punta de los Reyes, which is wholly composed of it, and at Bodega Head, farther north. Limestone is associated with granite and mica slates at the head of Tomales bay, and it is probably the continuation of the belt which traverses Santa Cruz and San Mateo counties.

Mount St. Helena, 4,343 feet high, at the head of Napa valley, is, with the single exception of Mt. Hamilton, the highest summit between San Carlos to the south and the higher regions to the north. This mountain seems to have been the source of the volcanic materials, which are spread over a large area of country to the east and southeast of it. A belt of eruptive rock extends from the west side of Clear Lake through to Suisun Bay. Hot springs, which have an extended reputation for their curative qualities, are numerous, especially in the vicinity of St. Helena, and Clear Lake. North of St. Helena are several localities where cinnabar has been found and mined to some extent.

Perhaps the most important development is in Pope Valley, three miles northeast of Mt. St. Helena. The rock, an imperfect serpentine,

sandstone in the process of metamorphism, is the same as is usually associated with the ore. At the Lake mine, about eighteen miles from the southern end of Clear Lake, on the Suisun road, the ore is peculiar, on account of its association with sulphuret of antimony in acicular crystals and granular masses, as well as by reason of the absence of the peculiar silicious rock with which cinnabar is generally found. It is deposited in lenticular masses in cretaceous shales.

The locality known as the Geysers is half-way between Healdsburg and the southern end of Clear Lake. The wild scenery, and the phenomena exhibited by the hot springs occurring there, make it an attractive and interesting locality to visit; but there exists no analogy between these and the Geysers of Iceland. The waters hold a variety of salts in solution, which give rise to numerous chemical reactions when waters from different sources are brought in contact, and produce vivid colorations of the rocks. These are chiefly sandstones and silicious slates, the silica of which is thoroughly leached out by hot alkaline solutions, and afterwards forms extensive deposits. Considerable quantities of sulphur are also deposited by the water from these springs, and the deposit known as the Sulphur bank, in the vicinity, may prove of future value.

One of the most interesting and curious portions of the Coast Ranges north of the Bay of San Francisco, is that in the neighborhood of the southern extremity of Clear Lake. It is in this vicinity that the celebrated and productive deposits of borax, or biborate of soda, occur beneath the waters of Borax Lake. This is a sheet of shallow water, the average depth of which is about three feet, comprising generally about one hundred acres in superficial area, but varying greatly in size with the seasons, as the shores are low, and their slope towards the water is very gradual. The water of the lake is impregnated with borax; analyses of it, made in 1863, show that it contained 2401.56 grains of solid matter to the gallon, about one half of which was common salt, one quarter carbonate of soda, and the remainder borate of soda, there being 281.48 grains of anhydrous biborate, equal to 535.08 of crystalized borax to the gallon. A sample taken from the interior of a coffer dam, from water percolating through the underlying mud, was found to contain a much larger portion of solid matter, but in the same proportion as before. The borax being the least soluble of the prominent ingredients, has crystalized out, and is found in the mud in crystals of various sizes, from two or three inches across, to those of microscopic size. That the process is rapid and still going on, is shown by the coating of crystals formed upon sticks of wood, which

have been immersed in the waters of the lake for but a short time. The principal deposit of the crystals is in a layer of blue mud of varying thickness, beneath which is mud without them.

Northeast from Borax Lake, and about a mile distant from it, on the borders of Clear Lake, is an extensive deposit of sulphur, where solfatara action is yet apparent. The volcanic rocks have been extensively fissured, and through the orifices and seams, steam and sulphurous vapors are constantly issuing. A large amount of sulphur has been deposited, the extent of which is uncertain, and can only be demonstrated by the pick and shovel, though it occurs over an area of several acres. The most interesting fact in connection with this deposit is the association of cinnabar with the sulphur, sometimes distinctly separated from it, in quartz evidently deposited from solution, but often thoroughly intermixed with it.

Another large deposit of sulphur, about two miles distant, occurs on what is locally known as Chalk Mountain, so called from its peculiarly white appearance, and still another at the Sulphur Springs, further east, on the road to Colusa. At neither of these localities does the sulphur appear to be contaminated with cinnabar, which marks the deposit on Clear Lake. At the latter locality, which promises to be much more extensive than was at first supposed, a good merchantable article is being produced, in considerable quantities, by simple distillation. The rocks at Chalk Mountain are extensively fissured, and much decomposed, by the action of steam and acid vapor, giving them a white and chalky appearance. The deposit here promises to prove extensive, at least large superficial areas of it exist; how deep they will prove, or how large a quantity of sulphur they will yield, is of course a matter of uncertainty. Springs yielding carbonated water are numerous in the vicinity of Chalk Mountain-it is often very agreeable to the taste.

Volcanic materials and hot springs occur on a line from Clear Lake east towards the Sacramento valley-and, as Prof. Whitney remarks, there is every evidence of a transverse fracture extending from the Geysers across the volcanic belt, of which Mt. St. Helena is the culminating point, to the Sacramento valley.

A curious association of gold, cinnabar, and bitumen occurs in what is known as the Manzanita tunnel, near Sulphur Springs, on the road from Clear Lake to Colusa. Beds of hydraulic limestone occur in the cretaceous strata near Benicia ; they occupy a position between the sandstones and the shales.

The beautifully variegated Suisun marble occurs in the sandstones

of the Pelevo hills, north of Suisun. It is the deposit of calcareous springs, and cannot be obtained in masses of sufficient size to make it very important as an ornamental stone.

SOUTH OF MONTEREY BAY.

North of latitude 35° 20′ the trend of the mountain chains forming the Coast Ranges is quite uniformly northwest and southeast, agreeing very closely with that of the coast north of that parallel. South of this line, however, we have a very marked change in the direction of the coast. On the north side of Santa Barbara channel it runs nearly east and west, and near San Luis Obispo we have the northern limit of a system of upheavals, in a direction transverse to that which has determined the trend of the main Monte Diablo, and other ranges to the north.

The Santa Lucia mountains extend from Carmelo bay, near the town of Monterey, southeast in an unbroken line, bordering the coast as far as San Luis Obispo, then curving to the east, finally become merged into the main Monte Diablo Range. They form a mass of rugged and unexplored mountains, in places over 5,000 feet in elevation. The western slope of the range is peculiarly abrupt and inaccessible.

The comparatively broad valley of the Salinas river, included between the Santa Lucia and Gavilan mountains, stretches to the southeast from the Bay of Monterey, a distance of nearly one hundred miles. The average breadth of the Santa Lucia range is about eigh teen miles. Granite is known to occur throughout the northern twenty or thirty miles. Metamorphic tertiary rocks, and miocene and pliocene strata, highly contorted, also occur.

The Polo Scrito hills, between the valley of the Carmelo river and that of the Salinas, and the San Antonio hills further south, are made up of the great bituminous slate formation of the tertiary age, which extends through California as far north as Cape Mendocino; above which are more recent formations. Portions of the tertiary are highly bituminous, and asphaltum is of frequent occurrence. Well marked terraces occur on the Salinas and its branches-the San Antonio and Mascimiento rivers. Near San Luis Obispo the range has a fan-like structure. Gold has been found in very limited quantities, and, at various points, copper stains occur; argentiferous galena is also found, but neither is likely to prove of importance-no well defined vein having been seen.