254 ANNUAL OF SCIENTIFIC DISCOVERY. 



might have been some connection between the production of gold and 

 the atmosphere, since, judging from these specimens, it is from the 

 superficial extremities of quartz veins that the richest branches of 

 gold have been derived, while vein-stones followed downward have 

 usually proved unproductive. Notwithstanding, there are cases, 

 chiefly on a small scale, as in the Hungarian mines, where gold 

 ore continues to ramify in vein stones to great depths ; yet it is a statis- 

 tical fact, that all the great masses of gold have been derived from 

 superficial detritus. This detritus should not be confounded with mod- 

 ern alluvial deposits. 



Mr. Murchison then entered upon a comparison between the gold 

 regions of the Ural and those of California, and showed, by means of 

 maps and sections of the former, and from the descriptions of the lat- 

 ter country, that there was a great coincidence in their mineralogical 

 structure, and that with these " constants" the same results obtained 

 in America as in the Ural. He contended, however, against the in- 

 ference, that any large tract of California would be found to be as uni- 

 formly auriferous as the banks and slopes of the upper tributaries of 

 the Sacramento. The breadth of the auriferous detritus of Califor- 

 nia had yet to be ascertained. As, however, the lower or coast 

 ridge, which passed by San Francisco, seemed to be in miniature what 

 the higher parallel mountains were upon a larger scale, in being com- 

 posed of greenstones, porphyries, grauwacke, sandstones, and quartz 

 rocks, it was probable that very much of the great intervening valley 

 of the Sacramento might be strewed over at intervals with auriferous 

 debris, 



In regard to views advanced by Sir R. I. Murchison, the President 

 of the Association stated, that he thought that, as geologists, they 

 should receive with caution the opinion that gold was more abundant 

 on the surface than at great depths; neither should they take it for 

 granted, that the gold-bearing mountains had a bearing from north to 

 south rather than from east to west, as in California, for example, 

 they differed somewhat from the position laid down, and the Pyrenees 

 differed completely. 



Prof. W. Rogers stated, that in Georgia and the Carolinas the gold 

 was uniformly imbedded in, or associated with, quartz rock, forming 

 veins in the talcose and micaceous schists and altered sandstones. 

 He had invariably, in all his researches, found that gold was generally 

 obtained by washing the alluvium in the beds or along the banks of 

 rivers. But these superficial deposits are generally very rapidly ex- 

 hausted from the wasteful mode of conducting the works. It is prob- 

 able that the difficulty of obtaining gold by mining is universal and 

 continued at all depths ; it is in part owing to the association of the 

 gold in solid rocks with iron pyrites, ores of copper, and lead, so 

 blended as to cause great trouble and expense in separating them ; 

 near the surface of the rocks this process seems to have been accom- 

 plished by atmospheric agency, for it is impossible to suppose that 

 gold was originally most pure and abundant over what is now the sur- 

 face. The general trend of the old metamorphic rocks in the United 

 States is northeast by southwest, and the gold veins conform to this 



