314 IRVING. 



mass. The values obtained are very high, running frequently 

 up to $iSO per ton, and in one instance ;^i,ooo per ton. 



From these descriptions it will appear that there is no marked 

 difference between the siliceous ores in the Carboniferous and 

 those in the Cambrian. Like them, they are to be ascribed to 

 the chemical action of siliceous solutions replacing calcite. 

 That they are vertical in the majority of cases, horizontal in the 

 case of the metallic streak, irregular as in the Ulster, is merely a 

 question of the direction and form of the fissures through which 

 the solutions obtained access to the limestone. Their existence 

 in the Ragged Top region would seem to indicate the probable 

 presence of extensive ore deposits in the Cambrian below. In- 

 deed it is probable that as the development of the latter class of 

 ores goes on the distribution of the shoots will prove to be much 

 more general than is at present apparent. 



D. Placers. 



The quarternary placers have been formed by the concentra- 

 tion of the gold derived from the Algonkian. They are distrib- 

 uted in considerable numbers in the neighborhood of the great 

 Homestake belt, and in fact in many of the gulches, which head 

 up into the Algonkian areas throughout the hills. Professor 

 Smith mentions them and says : " The yield from these work- 

 ings is relatively small, and there seem to be a few places where 

 the placers could be profitably worked on a larger scale ; never- 

 theless, they afford occupation to a large number of men, and 

 yield them a constant if small return." 



The placers in Beaver Creek, Bear Gulch and Iron Creek are 

 of this type, and, although occurring in the Carboniferous for- 

 mation, have undoubtedly derived their gold from the Al- 

 gonkian of Nigger Hill. When panned the gold is found 

 mingled with great quantities of tourmaline and cassiterite, and 

 innumerable small red garnets, which could have come from no 

 other source. 



The richest placers are, however, not directly formed from the 

 disintegrated Algonkian, but have been shown by Devereux to 



