396 GEOLOGY OF THE OOMSTOOK LODE. 



hand, the opening appears to be a result of non-conformity of the wall 

 surfaces brought into opposition. 



Lateral secretion. — The coursc of the asccuding waters appears to have 

 been much influenced by the nari'owness of the vein in the lower levels. It 

 is highly probable that on some straight or sinuous line, at depths greatly 

 exceeding those yet reached, the vein is closed nearly water-tight from one 

 end to the other. If so, water ascending in vast quantities, as it n)ust once 

 have done, would be forced into the network of capillary fissures which 

 pervades the east country. Having become saturated with solul)le sub- 

 stances by contact with the immense surface here exposed to its action, 

 it would seek the main fissure once more as the path of least resistance, 

 and there deposit quartz and ore through changes in physical conditions, or 

 in virtue of chemical reactions. It is not unlikely that concentration by 

 evaporation was an important influence in accelerating precipitation. The 

 character of the deposited quartz evidently varied greatly from time to time, 

 but though the causes wei*e probably very simple in their general nature, 

 the conditions under which they acted, considered in detail, must have been 

 exceedingly complicated. On the whole, the later deposits were probably 

 the richer, and it is not impossible that a part of the rich pockets and string- 

 ers was formed at the expense of older deposits of lower grade. 



The east wall of the Lode is in most places ver}- indistinct, though 

 occasionally, as at the Savage connection with the Sutro Tunnel, nothing 

 could be clearer. This is due in part to the percolation of strong currents 

 from the east country during the deposition of ore, and partly to dynamical 

 action on irregular deposits crossing the lines of motion. 



Probabilities for lower depths. — The CoMSToCK IS csseutially a dcposit at the con- 

 tact of diabase with underlying rocks, and so long as the hanging Avail shows 

 a heav}- body of diabase the prospects for ore are good, mei'e depth not being 

 likely to exert any prejudicial effect upon the ore-bearing character of the 

 vein. In the search for ores explorations should be confined to a moderate 

 distance from the diabase contact, for no important bonanza except the 

 Justice body has been found which does not extend to within a very short dis- 

 tance from this contact; nor are any bodies likely to occur far from it which 

 Avill pay the expense of discovery. The first condition for the formation of a 



