Trans. NV. Yo Aci Sct. 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 of 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 method 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. Hotsprings 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 occurring 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 
