1 882. f 173 Trans. N. V. Ac. Set, 



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 formed. 



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 JMines. 



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 rhyohte, with a narrow 

 band of volcanic tuft' 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 feet in 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 



