GEOLOGY. 343 



and 1 : G.932. Tlie upper coal of the Bernice basiu is largely mined and 

 sold as anthracite, but is softer, and lacks the usual conchoidal fracture, 

 resembling rather that of the Lykens Valley than the more eastern, 

 anthracites. 



CHEMICAL GEOLOGY. 



That watery solutions have been the efidcient agents in the formation 

 of metalliferous deposits is now generally admitted, alike for those con- 

 temporaneous with the stratification, and for posterior accumulations, 

 whether in cavities produced by erosion, as in limestone rocks, or in 

 fissures resulting from movements in the earth's crust. That the proc- 

 ess of the transport and deposition of metals by solutions has been 

 going on from very early geological periods to the present has also been 

 recognized. The comparative recency of deposits like the great gold 

 and silver bearing Comstock lode, for example, is well known, and Phil- 

 lips and Kolland have shown that thermal waters are even now giving 

 rise to deposits of sulphureted ores, which lead to the conclusion that 

 the great lode in question has been formed by mineral solutions, of which 

 the hot springs of the vicinity are the actual representatives; 



In the Coast Eange of California the Cretaceous and Tertiary strata 

 were greatly disturbed at the close of the Miocene, following which, as 

 is well known, was a period of volcanic activity prevailing through Plio- 

 cene time and perhaps later. The springs of heated waters charged 

 with soluble and gaseous sulphids {solfataras), still abundant in the re- 

 gion, are probably connected with this former vulcanism. Of this solfa- 

 taric action the Sulphur Bank, as it is called, on Clear Lake, ninety 

 miles north of San Francisco, furnishes a remarkable example. Here a 

 layer of volcanic rock, described as augite-andesite, which overlies the 

 highly inclined sedimentary strata, is found decayed at the surface to a 

 white granular earth, while lovrer down in the mass are " bowlders of 

 decomposition," consisting of nuclei of the same rock, still undecomposed. 

 The interstices of the mass are filled with crystalline sulphur, which in 

 descending is replaced by cinnabar. An open cutting to a depth of about 

 forty feet in the nearly vertical sedimentary strata, not far from the edge 

 of the volcanic cap, discloses between harder layers a stratum consist- 

 ing of a soft breccia of fragments of sandstone and shale, with interposed 

 bluish clay or mud, impregnated with cinnabar and pyrites, through 

 which rise hot alkaline waters, carrying sulphydric, carbonic, and boric 

 acids. The outcrop of this bed of rubble or breccia has been traced, and 

 elsewhere mined for cinnabar. 



Messrs. Joseph Le Conte and W. B. Eising have described further 

 observations made in levels driven from a shaft sunk with the object of 

 exploring the strata beneath the lava-cap. One level, at a depth of 150 

 feet, after traversing seventy feet or more of barren sandstone and shale, 

 comparatively drj'- and cool, reached a belt of brecciated rock made up 

 of fragments of sandstone and shale resembling that already described, 



