ACADEMY OF SCIENCES. 89 



Mr. Clayton gives the following section of the rocks in that 

 region : 



Feet. 

 Very brittle, chiefly limestone, with Productus, Spirifer, corals and flint 



nodules 1,000 



Greenish sandstone 60 



Black bituminous shales 400 



Encrinital limestone. . . .'. 60 



Pink shales and sandstones 300 



Silver-bearing limestone, with abundant corals and small bivalves 1,500 



He considers the silver-bearing rocks as probably of Silurian age. 

 In regard to the occurrence of the ore, he writes as follows : 



" The ore is found, first, in certain lines of fractured country rock, which I 

 call ' ore-channels,' or zoijes of metal-bearing country. The ore-channels have 

 been in all cases brecciated or crushed by mechanical movements of the earth's 

 crust, and sometimes extensive faults or vertical displacements are seen along 

 the crushed lines, but not always. In some of the most extensive brecciated 

 beds of limestone no material displacement has occurred ; as, for instance, in 

 the great Aurora ore-channel, which is one hundred to two hundred feet wide, 

 and one mass of broken limestone, the angular fragments being of all sizes, from 

 that of minute pieces to large blocks. In the interstices of this mass the quartz 

 and ore have been deposited, the small fragments being completely changed to 

 quartz, the large ones only pai^ially so. 



''Second — In layers between the bedding of the limestone in masses of all 

 shapes and sizes, from a few pounds in weight to hundreds of tons, always con- 

 necting immediately or remotely with some vertical fissure or brecciated chan- 

 nel of country rock. 



" Third — In vertical fissures, cutting the country to unknown depths ; but 

 there are no true veins of ore in these fissures; they are filled with silicified 

 breccia of the same general character as that found in the ore-channels. 



" Many of the true fissures are filled with banded spar veins ; but they are 

 barren and are of a later formation, in many cases cutting through the Ore 

 channels and country rock indiscriminately. There have evidently been two 

 periods in the changes made here : First — A partial upheaval, fracturing the 

 limestone beds, but not breaking the more flexible overlying shales, which thus 

 confined the heated waters and gases to the limestone. This was the quartz- 

 and ore-period. Second — An upheaval, breaking the whole series of overlying 

 rocks, making new fissures, reopening old ones, and depositing spar." 



Prof. Bolander spoke of the recently reported rise of six feet in 

 the waters of Mono Lake, said to be accompanied by a freshening 

 of the waters and the disappearance of the dense clouds of flies, 

 of which the larvse were formerly so abundant in the lake. 



Prof. Whitney stated that the ancient water-marks showed that 



Proc. Cal. Acad. Sci., Vol. IV.— 7 Feb. 1870. 



