52 MINING INDUSTEY. 



few little threads of silver were found, as is the case through all the quartz, 

 but they led to nothing. The Yellow Jacket, and a part of the Kentuck, have 

 now at their lowest level the only deep ore in the Gold Hill section. Regard- 

 ing these several bonanzas as a group or family, it is noticeable that the deepest 

 ore lies almost vertically under a point in their middle, and that north of this 

 central line have been the longest and richest deposits. 



The Virginia GtEOUP. — In the Virginia division the fissures have followed, 

 first, the contact plane between the propylite and older syenite; and, secondly, 

 have continued their northeast trend out into the propylite after the contact fis- 

 sure bent to the west, and, still diverging at an angle of 50°, the eastern fracture 

 has made a bold curve to the east, finally turning back again to join the west 

 wall in the Gould and Curry ground. The first section on Atlas-Plate 9 is 

 constructed through the Potosi south stope, almost on the plane of the ChoUar 

 shaft. On the level of the Potosi adit, 218 feet below the datum-point, the entire 

 vein was one mass of quartz for a breadth of 280 feet. Above that point it 

 divided into three spurs: one following the west wall upward at an angle of 45° 

 to the surface, maintaining a width of 50 feet; the middle mass, curving upward, 

 divides a great horse of propylite in two ; the third, having a width of 140 feet, 

 rises to its outcrop, separating the east horse from the east wall. From the adit 

 the quartz descends about 500 feet to a point just below the ChoUar-Potosi first 

 station, or 669 feet below the datum-point. The west wall, wherever developed 

 in this section, has a smooth, even face, and a regular dip of 45° east. The east 

 wall is much more nearly vertical, and therefore converges into contact with 

 the syenite. This junction, which is just below the the Chollar-Potosi first 

 station, marks the termination of the wedge of quartz. A thin selvage of dark 

 clay parts the vein from the syenite, and the ordinary thick, pebble-bearing 

 clay lies continuously between the vein and its east wall. The quartz forming 

 this- immense body changes frequently in texture, and shows the great variation 

 in dynamical influences which have modified all the Comstock materials. The 

 western spur, which follows the west wall, is hard, blocky, and characterized 

 by crystalline vugs, to a depth of 400 feet ; the middle one outcrops but feebly, 

 and is of a mechanical texture similar to the west; the east spur, on the con- 

 trary, more nearly resembles the crushed rock of the whole ore-channel. Both 

 horses included between these sheets of quartz are wholly of projjylite, and, as 



