J. A. PHILLIPS ON MINERAL VEINS. 395 
felspar. It is probable that the Comstock lode and the hot springs 
in the Steamboat Valley may have had a somewhat similar origin ; 
but, in the case of the former, volcanic agencies are no longer 
actively in operation, while both sulphur and sinter have long since 
been removed from the surface by denudation. 
Discussion, 
The Presipent remarked upon the interest of the paper in illus- 
trating the method of formation of mineral veins, and asked what 
the author’s opinion was as to the mode in which cinnabar and gold 
were brought up. 
Mr. Baverman said that in the district described by Mr. Phillips 
these phenomena were to be seen perhaps on the largest scale in 
the world. He thought that these deposits of sulphides of volatile 
metals illustrated those in other parts of the world, as at Almaden, 
in Spain. There the cinnabar occurred in a pit which was almost 
vertical, and might be described as a siliceous sponge infiltrated 
with cinnabar. At the Solfatara, Naples, sulphides of arsenic oc- 
curred in the same way ; and at Mieres, in Leon, arsenic and mercury 
were extracted from the same deposit. In these deposits also we 
had gold, probably reduced from a chloride by sulphide of mercury. 
Mr. Arrwoop corroborated the statements of the author from his 
knowledge of the district. Three years ago the lower workings of 
the Comstock lode, some 2300 feet below the surface, were found to 
be extremely warm, about 100° Fahr.; and at the same time the 
surrounding vein-matter contained only about 1 per cent. of sul- 
phides and about 99 per cent. of silica, showing that the decom- 
position of the sulphides could not produce the greatly increased 
temperature. 
Mr. Tenpron spoke of minesin Brazil where the heat was incon- 
siderable, and said that in those mines the gold was invisible and 
enclosed in either magnetic pyrites, ordinary iron-pyrites, or arse- 
nical pyrites, in the last in the greatest quantity, in the first the 
least ; there was also about 20 per cent. of silver. 
Prof. Jupp recalled the case of the volcano of Volcano, where 
there were many small vents depositing sulphide of arsenic, and at 
night a coloured hydrogen flame could be seen above these vents. 
Prof. Ramsay said he had always held that mineral bodies had 
been deposited from solutions, not sublimations, and inquired if the 
author thought it likely that in the case of the reefs of Australia, 
if they were deep beneath the surface and permeated by water, the 
gold might have been deposited from a state of solution in that 
water. 
Mr. Tenpron said that there was no ore in the joints in the 
clay-slate strata containing the mine he had described, but only in 
the fissure or walls of contact. 
The Aurnor said he had not attempted to explain the chemical 
actions which took place. The purpose of the paper was to show 
