Trans. N. V. Ac. Scz. 172 May 22, 



the Philadelphia mine ; but no section showing the tuff beds above 

 such fissures has been exposed. As these beds of tuff occur for many 

 miles along the base of the mountains, we may hope that the conditions 

 for charging them with sulphur have been many times repeated. Next 

 to the Cleveland mine, we should certainly look to the beds of tuff, along 

 the base ot the mountains eastward of Cove Creek, for the principal 

 supply of sulphur for economic purposes from this region. 



Owing to the exhalation of noxious gases in nearly all the prospects 

 that have been opened, we find in the bottoms of the excavations large 

 numbers of dead insects, together with the remains of mice, bats, rab- 

 bits, etc., that have been smothered by the escaping gases. In many 

 of the openings a choking sensation is felt, and the amount of gas, 

 which seems to be largely carbonic acid, is so great that a person can 

 remain in them but a few seconds. Even in shallow prospects the 

 workmen have to fan each other, in order to remain in the openings 

 long enough to do their work. These mines can only be opened from 

 the surface, and even by this melhod they cannot be worked to any 

 considerable depth, owing to the high temperature of some of the 

 prospects and the constant escape of noxious gases. 



Associated with the deposits of sulphur are beds of gypsum, and 

 also irregular deposits of " alum." Just what the nature of this " alum" 

 may be has not been determined by analysis. These beds usually 

 overlie the sulphur deposits, the alum being sometimes two feet 

 thick, and the gypsum as much as eight feet. Hot springs occur in the 

 same field, which, together with the feeble fumerole at the top of the 

 old crater, bear evidence of the expiring volcanic energy of the region. 



Sulphur Deposits at Humboldt House, Nevada. 



The sulphur at this locality has been reported as occuiring in nearly 

 vertical fissures that are associated with recent basaltic buttes. Careful 

 search was made by the writer, however, for fissures answering these 

 conditions, while examining the surface geology of the Humboldt Valley, 

 without successful results. The only sulphur deposits that could be 

 found in the vicinity, and the only ones known to the people living at 

 Humboldt House, occur in the craters of extinct hot springs. These 

 craters are situated about half a mile southward of Humboldt House, 

 on the open sage-brush desert, and rise to the height of from twenty to 

 fifty feet, as nearly as could be estimated. Nearly all of the cones are 

 weathered and broken down, and all are extinct, the water now rising 

 to the surface for miles around. The outer surface of the cones is com- 

 posed of calcareous tufa and silicious sinter, forming irregular imbri- 

 cated sheets that slope away at a low angle from the orifice at the top. 

 The interiors of these structures are filled with crystalline gypsum, that 



