Notes on the chemical geology of the gold-fields of California / by J. Arthur Phillips.

  • Phillips, J. Arthur (John Arthur), 1822-1887.
Date:
[1868]
Catalogue details

Licence: Public Domain Mark

Credit: Notes on the chemical geology of the gold-fields of California / by J. Arthur Phillips. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    tlie level of the sea, at the foot of the eastern declivity of the Sierra Nevada. The rock in this locality presents several parallel fissures, either giving out heated water or simply ejecting steam. The first principal group of crevices comprises five longitudinal openings extending in a straight line for a distance of 3500 feet. Their general direction is north 6° west, and they are comprised within a band of about 600 feet in width. The fissures are se- ])arated from one another by intervals of from 40 to 60 feet, have each a thickness of about 12 inches, and are severally con- nected with each other by lesser openings, which intersect the first nearly at right angles. These crevices are often full of boiling water, which sometimes overflows and escapes in the form of a rivulet, whilst at others it does not flow over, but violent ebullition is heard to be taking place at a short distance below the surface. The fissures are par- tially filled by a siliceous incrustation which is being constantly deposited on the sides, whilst a longitudinal central crevice allows of the escape of boiling water or steam. On the most eastern of these lines of fracture are several active centres of eruption, from which boiling water is often ejected to a height of from 8 to 10 feet. These waters are alkaline, and contain, in addition to car- bonate of soda, the sulphate of that base, with chloride of sodium. There is also everywhere an escape of carbonic acid, whilst from some places sulphuretted hydrogen is also evolved. These pro- ducts give rise to the deposition of sulphur, silica, and oxide of iron. The silica forms semicrystalline bands parallel with the walls of the fissures; and spongy deposits accumulate around some of the points of most active emergence in such a way as to form small circular basins, of which the edges go on continually in- creasing in height, so that each finally presents the appearance of a small volcano of boiling water. At a considerable distance to the west of these, a second group having the same origin is observed; but this is no longer tra- versed by hot water, although it still gives off steam and carbonic acid at various points. This large dyke of quartz commences at its southern extremity by a number of fissures which subse- quently converge into a single crevice, of which the two walls are of silica, and extend a distance of considerably over a mile. At its northern extremity a central fissure still remains open ; but in other localities it is for the most part obstructed by siliceous concretions. Towards the south the siliceous deposits extended beyond the edges of the cleft, and have accumulated on the surface of the ground to a thickness of several feet, and for a distance of from 80 to 90 feet on each side of the fissure. These deposits almost entirely consist of more or less hydrated silica.