130 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES. 



by our party, and the information we received from hunters and 

 others, famihar with the surrounding country, renders it more 

 than probable that the same beds, containing similar masses of 

 silicified wood, extend over a much greater area. 



The fossil trees washing out of this volcanic tufa were 

 mostly of great size, and appeared to be closely related to some 

 of the modern forests of the Pacific Coast, especially the gigantic 

 Conifers. One of the prostrate trunks examined during our ex- 

 plorations was partly exposed above the surface, dipping with the 

 strata about lo degrees to the northward. Its accessible portion, 

 evidently but a small part of the original tree, measured sixty- 

 three feet in length, and, although denuded of its bark and very 

 much weathered, was over seven feet in diameter near its smaller 

 end. All the trees discovered were prostrate, and most of them, 

 after their petrifaction, had been broken transversely into several 

 sections, apparently by the disturbance of the enclosing strata. A 

 majority of the trunks had a general north and south direction, 

 probably due to the course of the current that covered them with 

 volcanic eruption. Portions of nearly one hundred distinct trees, 

 tion in which they had fallen. Several of the trunks had por- 

 tions of their roots still attached, and some were evidently much 

 decayed internally and worm eatei'' before their entombment. 

 All the fossil wood observed was silicified, by means of hot alka- 

 line waters containing silica in solution, a natural result of vol- 

 canic action, especially when occurring with water, as was evi- 

 dently the case in the present instance. 



"Our party discovered on the western side of the ^s'apa val- 

 ley, along the base of the ridge, patches of a deposit of stratified 

 tufa and gravel, which was evidently identical with that contain- 

 ing the fossil trees on the summit. This would seem to implv 

 that the upper portion of the valley had once been filled with 

 these peculiar beds, and^ through their denudation, gradually as- 

 sumed its present proportions. However that may be, this vol- 

 canic deposit and its contents is certainly of great interest, even 

 in this land of geological wonders." 



The "Auriferous Gravels" and the "Dead Rivers" of the 

 western slopes of the Sierra Nevadas, are noted localities for the 

 variety of fossil wood called "Wood Opal" found in the mines. 

 Many of the specimens found, especially those of a fragmentary 

 character, are gem-like in their beauty of coloring and markings ; 

 black, browns, reds, yellows, grays and white in all the combina- 

 tions ; massive, fibrous, friable, opaque and translucent and inter- 

 mediate characters have been found in the gravels. Immense 

 trees are often "piped" out in the process of hydraulic mining 

 for gold ; some of them are almost adamantine in their hardness ; 

 others vary greatly in their character; irregularly shaped, chalce- 

 donic, or jaspery masses, compact as quartz crystals, are imbedded 



