204 On the Temperature of the Mines in Cornwall. © 
water is held to exist in muriatic acid gas to the amount of one- 
fourth of its weight ; and it is conceivable, that by some exer- 
tion of affinities, a portion of it may be liberated. If we were | 
unable to explain the modus operandi, this would remain a diffi- 
culty no doubt, but not, as in the opposite system, an impossible 
result. 
It is to be admitted, indeed, that in none of these cases is 
the entire quantity of water which must be supposed to exist in 
muriatic acid gas obtained; and so far the proof is deficient. 
But neither from the nature of the experiment is this to be looked 
for; and I give more weight to the argument, from having al- 
ways found certain portions of water to be procured, while, on 
the opposite doctrine, there should be none. In those cases 
where, supposing water to be present in muriatie acid gas, it 
ought to be obtained in the full quantity, it uniformly is so, 
though the proof from these is rendered ambiguous by the result 
being capable of being explained on a different hypothesis. 
. [To be continued. ] 
ooo. 
XXX. On the Temperature of the Mines in Cornwall. By 
Mr. Tuomas LEan, 
7 To Mr. Tilloch. 
Sir, — I was requested in the year 1815, by a member of the 
Cornwall Geological Society, to make some observations on the 
temperature of the air in the mine of Wheal Abraham, in the 
parish of Crowan, in this county. This mine is opened to the 
depth of 200 fathoms from the surface, and produces a consider- 
able quantity of copper ore ;—the vein in which the copper ore 
(sulphuret of copper) is found, contains (sometimes) a small _ 
quantity of tin ore, zinc ore, lead ore, and iron ore ;—and ge- 
nerally a considerable portion of mundie. ‘The metallic ores are- 
imbedded in quartz and feltspar. The first observations which 
I made was on the 9th of June; and were made in a shaft in 
which a current of air is generally ascending through the mine.: 
The thermometer /Fahrenheit’s) when exposed for some time to 
the sun stood at 74°, and in the shade at 59°; and in the mine 
at different depths from the surface as mentioned below ; viz. 
At 3 fathoms the thermometer stood at 65° 
20 ws ee aie eh 644 
50 via sis a is 67 
80 oe °° °° ee 68 
100 ok as ee ee 654 
120 ar ve ‘* on 69 
140 . x Pa eg 62} 
