wever, the
waters with their contents were released from internal pressure and
began to lose their heat the gold would be precipitated together with
the salts of some other metals, and would, where the waters could
percolate, begin to accretionise, thus forming the heavy or specimen
gold of some reefs. On this class of deposition I shall have more to say
when treating of the origin of alluvial gold in the form of nuggets.

Mr. G. F. Becker, of the United States Geological Survey, writing of
the geology of the Comstock lode, says:--"Baron Von Richthofen was of
opinion that fluorine and chlorine had played a large part of the ore
deposition in the Comstock, and this the writer is not disposed to
deny; but, on the other hand, it is plain that most of the phenomena are
sufficiently accounted for on the supposition that the agents have been
merely solutions of carbonic and hydro-sulphuric acids. These reagents
will attack the bisilicates and felspars. The result would be carbonates
and sulphides of metals, earth, alkalies, and free quartz, but quartz
and sulphides of the metals are soluble in solutions of carbonates and
sulphides of the earths and alkalies, and the essential constituents of
the ore might, therefore, readily be conveyed to openings in the
vein where they would have been deposited on relief of pressure and
diminution of temperature. An advance boring on the 3000 ft. level of
the Yellow Jacket struck a powerful stream of water at 3065 ft. (in the
west country), which was heavily charged with hydrogen sulphide, and
had a temperature of 170 degrees F., and there is equal evidence of the
presence of carbonic acid in the water of the lower levels. A spring on
the 2700 ft. level of the Yellow Jacket which showed a temperature
of about 150 degrees F., was found to be depositing a sinter largely
composed of carbonates."

It may be worth while here to speak of the probable reason why gold, and
indeed almost all the metals generally occur in shutes in the lodes; and
why, as is often the case, these shutes are found to be more or less in
a line with each other in parallel lodes, and why also the junction of
two lodes is frequently specially productive. The theory with respect
to these phenomena which appears most feasible is, that at these points
certain chemical action has taken place, by which the deposition of the
metals has been specially induced. Generally a careful examination of
the enclosing rocks where the shut