26 SILVER-LEAD DEPOSITS OF EUEEKA, NEVADA. 



may be its angle of dip, but it is apparently less than 45°, and the shale pitches 

 to the northeast away from the fissure. As this formation will be described 

 at length hereafter, it is only necessary to mention it here in reference to the 

 fault. It is evident that the country southwest or on the foot-wall side of 

 this fissure has been raised many hundred feet relatively to the hanging 

 wall. Whether the former was raised or the latter subsided is immaterial, 

 as the same effect would be produced in either case. It is probable, how- 

 ever, that there was both subsidence and upheaval, but that the latter 

 exceeded the former. In the Eureka mine the distance to which the south- 

 west wall has been raised relatively to the northeast wall is over 1,400 feet. 

 The faulting action is represented in Plate IV. Fig. 1 is an ideal section of the 

 country through the junction of theLocan shaft cross-cut and the twelfth level 

 of the Eureka mine, on a line at right angles to the strike of the fault which 

 is represented by the line X Y. The order of succession of the formations, 

 beginning at the lowest, is : Prospect Mountain quartzite; Prospect Mountain 

 limestone, consisting of two beds of limestone, with an intercalated bed of 

 shale; Secret Canon shale; Hamburg limestone; Hamburg shale ; Pogonip 

 limestone. Fig. 2 represents the position of the different formations after 

 the faulting and uplifting of the foot wall, and after the erosion of the over- 

 lying formations had given the country its present configuration. It will 

 be noticed that the intercalated belt of shale to the southwest of the fissure 

 has been eroded as well as the upper stratum of Prospect Mountain lime- 

 stone. In the Eureka mine the lower shale is not found much above the 

 little tenth level (830 feet below the top of the Lawton shaft), but in the Jack- 

 son it appears above the third level (315 feet below the top of the Jackson 

 shaft). In the Richmond mine it is exposed from the surface down to 

 nearly the deepest workings, but as the shale in the Richmond is of a com- 

 plicated structure its discussion will be postponed until the shale itself is 

 examined. One of the remarkable features of this widely extended Ruby 

 Hill fault, which runs in an unbroken line from beyond the Jackson to the 

 Albion, is its extreme regularity when compared with the contact planes of 

 the three formations, quartzite, limestone, and shale. In breaking through 

 these formations it seems to have been but little influenced by the difference 

 in their cohesion. In the Richmond mine, crushed limestone occupies the 



