J, A. PHILLIPS ON MINERAL VEINS, 393 
recent formation of a considerable metalliferous deposit by the agency 
of hot springs; and I am, again through the kindness of Mr. Att- 
wood, enabled to lay before the Society a specimen of cinnabar from 
this place. 
In further illustration of the subject I may mention the deposit 
of bright red cinnabar in a brecciated vein-mass near the hot springs 
at Calistoga, at the foot of Mount St. Helena. Here fragments 
of an amorphous siliceous rock are cemented together by crystallized 
quartz showing distinct lines of accretion ; and throughout this minute 
granules of sulphide of mercury are plentifully disseminated. <A 
hand specimen and a thin section of this veinstone are on the table. 
The Great Comstock lode is, as before stated, situate in a volcanic 
district seven miles south-east of Steamboat Springs, has a nearly 
similar orientation, and is enclosed between walls either of propylite 
or of diorite on one side and of propylite on the other. This vein, 
of which the gangue is chiefly siliceous, although calcite is also 
sometimes present, was first attacked by the miner in the year 
1859, and since that time has yielded silver and gold to the esti- 
mated value of above £60,000,000. 
The température of the waters issuing from mines worked upon 
the Comstock lode has always been somewhat high, but it was not 
until they had attained a very considerable depth below the surface 
that the workmen first became inconvenienced by extraordinary heat. 
At their present greatest depth (2660 feet) water issues from the 
rock at a temperature of 157° Fahr. (70° C.); and, according to Prof. 
John A. Church, of Ohio, who has recently published a valuable 
paper on the heat of the Comstock mines, at least 4,200,000 tons of 
water are now annually pumped from the workings at a minimum 
temperature of 135° Fahr.* He also estimates that to elevate 
such a large volume of water from the mean temperature of the 
atmosphere to that which it attains in the mines, would require 
47,700 tons of coal. In addition to this, however, 7859 tons of 
coal would, he calculates, be required to supply the heat absorbed 
by the air which passes along the various shafts and galleries through 
which it is diverted for the purposes of ventilation. It follows, 
therefore, that to develop the total amount of heat necessary to 
raise the water and air circulating in these mines from the mean 
temperature of the atmosphere to that which they respectively 
attain, 55,560 tons of coal or 97,700 cords of firewood would be 
annually required. 
Prof. Church, in his paper, quotes four distinct analyses of waters 
from the Comstock lode taken at different depths; these, as might 
have been anticipated, vary somewhat as to the relative proportions 
of the various substances present; but they contain on an average 
42-62 grains of solid matter to the gallon. Of this amount, 20°74 
grains are calcic sulphate, 12°13 grains carbonate of potassium, 
4°85 grains carbonate of sodium, and °66 grain of chloride of sodium. 
* «The Heat of the Comstock Mines,” by John A. Church, E.M., Professor 
of Mining in the Ohio State University. Presented to the American Institute 
of Mining Engineers at the Chattanooga Meeting, May 1878. 
