248 BUREAU OF AMERICAN ETHNOLOGY [bull. 60 



As developed by the recent operations, it appears that the ancient 

 work along the vein reached in places a depth of 30 to 40 feet, the 

 modern shafts having gone much deeper. In clearing out the old 

 trenches the white miners observed that the ancient excavations 

 were very narrow at the bottom, hardly wider than the vein itself, 

 which varies from 1 to 5 feet in thickness. In descending it was 

 found that the vein dips slightly to the southeast. 



The northern or Sink Hole group comprises a remarkable series of 

 ancient pittings, beginning near the base of a low spur a quarter of 

 a mile northeast of the Robinson group, on the same strike, and 

 extending to the crest of the hill and somewhat beyond, a total 

 length of about 1,000 feet. There are two separate and independent 

 lines of the excavations. The lower line corresponds closely in 

 character and extent with the Robinson mine, the pittings left by the 

 aborigines being well filled in places by the material derived from 



Fig. 110. Section of the Roliinson mine. 



the deep shafts sunk along the vein by the modern miners. The old 

 diggings reached in places 30 to 40 feet in depth, the mica vein aver- 

 aging from 4 to 8 feet in width and dipping at a steep angle to the 

 southeast. A section of this group corresponds closely with that 

 of the Robinson mine. Just above the upper end of the deep digging 

 is a small round depression 30 feet in diameter and perhaps 15 feet 

 deep, which represents an unsuccessful attempt of the aborigines 

 to discover a continuation of the vein, which, it appears, had been 

 lost at the upper end of the main excavation just described. 



The upper line of works is offset from the first as indicated on the 

 map, the distance between the two axes being 30 to 40 feet. It re- 

 mains a question whether this offsetting is due to the existence of a 

 separately developed vein or to a faulting of a formerly continuous 

 vein. The latter theory is supported by the fact that the upper end 

 of the one appears to coincide with the lower end of the other, there 



