1882. 173 Trans. N. Y. Ac. Sez. 
in at least two instances is impregnated with sulphur. One of the cones 
has been opened by a cut from the side in such a manner as to expose 
a good section of the material filling the interior, and a few tons of the 
sulphur and gypsum removed. The percentage of sulphur is small, 
and the economic importance of the deposit, as shown by the excava- 
tion already made, will not warrant the further expenditure of capital. 
The cone that has been opened is surrounded on all sides by a large 
deposit of calcareous and silicious material, thus forming a low dome 
or crater, with a base many times as great in diameter as the height of 
the deposit. 
These cones correspond in all their essential features with the struc- 
tures that surround hot springs that are still active in various parts of 
the Great Basin, thus leaving no question as to their origin. They are 
situated within the basin of Lake Lahontan, and must have been formed 
and become extinct since the old lake evaporated away. 
Sulphur is reported as occurring in the chemically formed deposits 
that surround Steamboat Springs, situated midway between Carson and 
Reno, Nevada. The conditions at these springs must be very similar 
to what existed near Humboldt House, at the time the cones containing 
the sulphur were tormed. 
Sulphur is also said to occur in the Sweetwater Mountains, situated 
on the boundary between California and Nevada, in latitude 38° 30’; 
the extent and geological relations of these deposits are unknown. 
The Rabbit Hole Sulphur Mines. 
These mines are located in northwestern Nevada, on the eastern bor- 
der of the Black Rock Desert, and derive their name from the Rabbit 
Hole Springs, a few miles to the southward. ‘The hills bordering the 
Black Rock Desert on the east are mainly of rhyolite, with a narrow 
band of volcanic tuff along the immediate edge of the desert. These 
beds of tuff are stratified and evidently water-laid, and are identical 
with tuff deposits that occur over an immense area in Oregon and 
Nevada. At the sulphur mines, the tuffs contain angular fragments of 
volcanic rock and are cemented by opal and other silicious infiltrations 
since their deposition, so that they now form brittle silicious rocks with 
pebbles and fragments of older rocks scattered through the mass. In 
many places these porous tuffs and breccias are richly charged with sul- 
phur,which fills all the interstices of the rock and sometimes lines large 
cavities with layers of crystals five or six feetin thickness. In the Rabbit 
Hole district, sulphur has been found in paying quantities for a distance 
of several miles along the border of the desert, but the distribution is 
irregular and uncertain, and is always superficial, so far as can be judged 
by the present openings. As in the Cove Creek mines, the sulphur at 
