426 Mr. J. A. Phillips's Notes on the Chemical Geology 



the 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- 

 parated 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 thefissures; 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. 



