1822.) | Mr. Fox on the Temperature of Mines. 447 
The high temperature in mines seems to have no necessary 
connexion with the minerals which they contain, since where 
iron pyrites is very abundant, the heat does not appear to be 
greater than where it is the reverse. 
If, as we may conclude from the evidence adduced from 
various quarters, that the high temperature which exists under 
the surface of the earth does not arise from causes merely local 
or accidental, must we not suppose it either to have been 
imparted to the globe at its creation, or attribute it to some 
cause constantly in operation? If the former hypothesis be 
adopted, it cannot readily be conceived that the heat is con- 
ducted towards the circumference of the earth, by the solid 
substances of which it is composed ; for if so, the internal heat 
must be intensely, and indeed incredibly great; besides, many 
facts oppose this conclusion; among which it may be proper to 
notice that granite, and other hard rocks, are generally of rather 
an inferior temperature compared with clay-slate, and other more 
porous and softer rocks, which are worse conductors of caloric. 
It is true we may imagine water and vapour to convey and dif- 
fuse heat from the interior of the globe towards the surface, and 
not necessarily adopt the conclusion, that the heat must be so 
intense at the centre ; but, without setting aside the agency of 
water and vapour in circulating and equalizing the temperature, 
may if not with more probability be supposed to depend upon 
some constantly operating cause? If electricity, for instance, be 
evolved when several different mineral substances are brought 
into contact, and likewise in the process of crystallization, &c. 
may it not, in connexion with the strata and veins, and the 
almost distinct portions of water which abound in the earth, 
also act its part on a larger scale, and not only excite heat, but 
contribute to produce the extraordinary aggregation and posi- 
tion of homogeneous minerals in veins, &c. and the beautiful 
order which exists even under the surface of the earth? I venture 
to bring this forward merely as a suggestion, hoping, if it be 
thought to deserve any attention, that others more competent 
than myself will investigate the subject. 
Note.—I will here mention a fact which I consider to be con- 
nected with electricity. Having fastened a piece of iron pyrites 
with a brass wire in a moss house, the moss being damp, | found 
on the following day that the wire was broken, and excessively 
brittle, and the parts which had touched the pyrites were much cor- 
roded. On one occasion, after the brass wire had been fastened 
once or twice round a piece of iron pyrites, and had remained for 
some days enveloped in damp linen, the constituents of the 
brass wire were separated, and it was converted into copper 
wire coated with zinc. 
Having recently tried some experiments on the water taken 
