56 MINING INDUSTEY. 



of the Chollar-Potosi, in both sections of this Plate, may be seen lying upon 

 the west wall a considerable mass of syenite, defined upon the west by a clay. 

 These bodies are unlike the west country syenite in that they are decomposed 

 by chemical action, usually, it is true, much less than the propylite material, 

 yet so far as to lose their coherent texture and become softened and, in a meas- 

 ure, plastic. 



The ore-bodies south of the Hale and Norcross line are confined to levels 

 within 500 feet of the surface. The most southern, or Blue Wing, is cut in 

 the Potosi-south-stope section and may be also studied on Atlas-Plate 4, where 

 the expanded levels overlying one another are horizontal cuts of its most promi- 

 nent portions. On Atlas-Plate 7 it is shown in vertical elevation directly back 

 of the Potosi shaft. With a width on the surface of 160 feet it descends to 

 360 feet. As was remarked of the Gold Hill bonanzas, these limits only indi- 

 cate the extent of ore that carried not less than $25 to the ton. A very large 

 portion of the vast quartz body lying to the west, north, and south of this stope 

 contain sufficient silver to warrant working at present labor prices, and in the 

 course of the next two years the boundaries of the bonanza must be con- 

 siderably enlarged. Next north of this lies the Potosi bonanza, a large and 

 valuable body which, on the level of the Potosi adit, extends from north to 

 south 450 feet. Its greatest downward extension was on a line dipping 

 toward the south and extending from its upper limits 600 feet. 



Lying west of this in the upper levels was a small, irregular body, also 

 laid down on Atlas -Plate 7. A cross-section through the Hale and Norcross 

 lower works, from the 787 to the 1,338-foot level. Fig. 3, Atlas-Plate 12, 

 shows the arrangement of the quartz and ore at the present bottom-level. 

 The seam which had followed the east wall to the 750-foot level leaves it and 

 curves downward into the middle of the vein. A deposit of ore occupies its 

 central position down to the 1,000-foot level. On the 1,170-foot level a thin, 

 limited bunch of silver edged its western termination. At the 1,000-foot level 

 a new body of quartz made its appearance in the eastern wall ; its position 

 is shown on Atlas-Plate 12. This important new body carries its ore on 

 the eastern side, and includes within its crushed mass brecciated bits of 

 propylite. 



