EXPERIMENTS ON VEINS AND MINES. 137 
both of them inferior in this respect to large porous lodes or 
veins*. ‘Thermal springs may likewise, I conceive, be referred 
to the same cause, and it is well known that they are generally 
connected with fissures or faults; moreover, I may here remark 
that this property of fluids must more or less influence the 
temperature of water in Artesian wells, so that thermometrical 
experiments made in them are often rather calculated to prove 
the existence of subterranean heat than to ascertain its ratio of 
increase in descending from the surface. 
Since the foregoing report was read at the geological section, 
I have obtained some results relative to the temperature of 
Tresavean Copper Mine from Captain Oats, who kindly made 
the experiments for me. The mine is worked almost wholly 
in granite, and is situated in the parish of Stythians, about three 
miles to the S.W. of the Consolidated Mines. The bulb of the 
thermometer No. 1 was buried 2 feet 10 inches, and that of No. 
2 one ineh under the surface of the rock at the different stations, 
their stems having in all cases been surrounded by clay pressed 
into the holes. The following were the results : 
Depth in fathoms. Experiments made. 
from from Inair. Inthe rock. 
surface, sea level. No. 1. No. 2. 
, ° ° ° 
26 . ... In pranite 15 fathoms N. of lode, and 40 fathoms 53:3 57: 598 
AVON MAS, Aeasdecscacecs eco cnaincsveussles ebnahenie 
ec i 
200. 170 ae lode, rock do., ‘‘ killas,” and three fathoms } 17:9 76+ 155 
YOM SYANite ......sececeeoes seeeescecenseececceccesess 
200 170 In do. 10 fathoms from do. ....cceccccceesceees dederease tet LUG, eon 
250 196 ee eopienet in granite, and 60 sage from §3°2 82:5 82 
2 
262 208 Inlode,do.,in7 fathoms from do. , being the bottom 855 82:5 82: 
GLiMMEMNINC wpe beeteces ckeadaesescesnecinacvcndes 
_ The last result gives a ratio of increase of 1° in 48 feet, cal- 
culated from the surface. It will be seen that the elevation of 
the latter, in reference to the sea-level, varies considerably in 
different parts of the mine. 
* See Philosophical Magazine and Annals, 1831, vol. ix., p. 94. 
