318 REPORT—1840. 
a, b, and ¢, in the section, each represent the deepest part of 
a mine, all three being in killas. If fissures or veins, pervious 
to water, be supposed to descend from these points to a much 
greater depth, where the temperature is considerably higher, 
it is evident that the warmer water will rise, and the cooler 
sink and take its place; and thus an excess of temperature will 
be imparted to a, b, and ¢ by the agency of the circulating 
water. It matters not whether the ascending currents proceed 
from d in the killas, or f in the granite, or through the line of 
junction # e, to b or ¢; in any of these cases corresponding 
effects will be produced, and a, b, and e will be at a higher 
temperature than other points at equal depths in their vicinity, 
more or less distant from fissures, veins, etc.; the former dif- 
fering only in degree according to the depth, or rather tempe- 
rature of the parts where the currents originate, and the 
obstacles they meet with in their passage. Nos. 51, 52 and 
53, in Table I., may be referred to as examples of this differ- 
ence. In this case, the vein in the Consolidated Mines, at 
290 fathoms deep, was found to be at 92°, whilst the rock at 
the same depth, and only 10 fathoms from it, was at 86° 3'; 
and at 24 fathoms from it, 85° 3!. These facts, with others 
which might be mentioned, seem to show how poor a con- 
ductor of heat the rock is, and they give additional support to 
the views advocated in this Report. 
The circulation of water under the surface, and its influence 
on subterranean temperature, is moreover, I apprehend, pro- 
moted by the agency of electricity, which is in such active 
operation in metalliferous veins*, since it will cause water to 
pass through many substances that would otherwise be imper- 
vious to it. The simplest, and almost the feeblest voltaic 
combinations, are capable of illustrating this remarkable pro- 
perty, and will transmit water, especially if it contain saline 
ingredients, through the most tenacious clay, etc., in any direc 
tion, either horizontally or vertically. 
I will now conclude this Report with the expression of a 
hope, that the ratio of the increase of subterranean tempera- 
ture may be more fully investigated, not only in this country 
but also in others, where the climates are the most dissimi- 
lart, in order to determine the modifications produced by 
* T observe, by the Edinburgh New Philosophical Journal, No. 55, that 
Prof. Reich has detected electric currents in Himmelfahrt Mine, near Frey- 
berg, although they were evidently much less energetic than those prevailing 
in our mines of copper, etc. 
+ Note.—Might not this object be accomplished, as it respects some of the 
mines in America, through the instrumentality of the mining companies, if 
