THE OEE DEPOSITS. 71 



is rare. The rarity of this type of regular deposits at Eureka can be 

 accounted for in a great measure if the extremely crushed character of the 

 country surrounding them is taken into account. When the upheaval of 

 the mountain ranges began, the rock was cracked and fissured in many direc- 

 tions, the fissures no doubt extending to great depths and having consid- 

 erable lateral extent; but as the uplifting and grinding process was pro- 

 longed, these fissures themselves were in a great measure obliterated and 

 faulted, new ones of less magnitude taking their place. This operation 

 seems to have been carried on until the mountain was no longer a solid 

 mass penetrated by great cracks, but was composed of shattered zones of 

 limestone separated here and there by bodies of unbroken rock. The ore- 

 bearing solutions entered the rock through the channels of least resistance, 

 the crushed limestone offering less resistance in many places than the main 

 fissures themselves, and deposition followed in forms of a degree of irregu- 

 larity corresponding to the complexity of the preceding dynamical effects. 



Disposition of the ore in the chambers. — The ore in the upper part of larger cham- 

 bers is mostly in a loose state, sometimes in layers, and is usually covered 

 by beds of sand, gravel, and bowlders of variable thickness. It is difficult 

 to believe that this mass owes its structure to any other cause than rearrange- 

 ment by subterranean water currents, though it is not likely that the original 

 position of the material was remote from that which it now occupies. There 

 is of course every reason to suppose that waters either from the surface or 

 from below have flowed through these rocks in notable quantities ever since 

 thev were intersected by fissures, but the floods which have left the traces 

 just described in the upper portions of the chambers must be comparatively 

 recent, since the stratified ore has been rearranged since its oxidation. In 

 the lower part of the chambers, on the other hand, the ore is more compact 

 and usually appears as if it occupied its original position. 



Connection of ore bodies with the quartzite. On Ruby Hill, in the mines lving SOUtll- 



east of the "compromise line," the ore is usually found in the limestone at 

 or near its contact with the quartzite, except close to the surface, where it 

 is generally at some distance from that formation. Although a complete 

 connection has not been established between all these ore bodies and the 

 quartzite, or between all the ore bodies themselves, yet their location and 



