306 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. 



The clay wall, then, appears to me to mark a fault which has dislocated 

 the ore-bearing ground. This fault has certainly not passed by the deposits, 

 for it has cut off the New Hope lode from the other ore bodies. The hang- 

 ing side of this clay wall has been little explored. I consider it the most 

 hopeful portion of the property and believe that explorations should be 

 made in it. I have no data tending to show the amount of the fault or even 

 its direction , but, according to the general rule, ore bodies, if they exist and 

 were once continuous with the stockworks, will be found at lower levels on 

 the hanging side of the fault. The Elvan Streak and the New Hope appear 

 to me to mark the direction of the main fissures of the mine. The disturb- 

 ances which made room for the stockworks were probably contemporaneous 

 with those which produced these veins. There is no evidence of a lapse of 

 time between them and it is not difficult to understand how the two sets of 

 ruptures may have been brought about simultaneously. Where a fracture 

 is accompanied by torsion, two sets of fissures form at a large angle to each 

 other. This has been demonstrated experimentally by Mr. Daubr^e. The 

 Coast Ranges are full of evidences of torsional fractures. At New Idria 

 and elsewhere highly indurated shales are very common, which, even in 

 small fragments, exhibit innumerable cracks, often filled with quartz, 

 which are divisible into two systems nearly at right angles to each other. 

 There is plenty of evidence, too, that fractures like those produced on a 

 small scale are formed also on a large one. When a mass is broken under 

 a torsional stress, the force will not in general be equally resolved in two 

 directions perpendicular to each other and the intensity of the disturbance 

 will be greater on one set of ruptures than on the other. The more violent a 

 rupture in the rocks is, other things being equal, the cleaner will be the fis- 

 sures produced, just as a rifle-bullet makes a round hole in a pane of glass, 

 while a body moving at a low velocity crushes the whole pane to fragments. 

 The ill defined zones of broken rock which led to the formation of stock- 

 works resulted from disturbances less violent than those which produced 

 the vein fissures ; but the two sets of ruptures, in my opinion, were due 

 to one cause, a torsional stress, and were produced at the same time. In 

 searching for ore these vein fissures, and perhaps others parallel to them, 

 should serve as guides. Other stockworks may very likely be found and 



