(m Subterranean Temperatures. 289 



men, with respect to the running or stagnant waters, there is yet 

 remaining a great number of observations, whose testimony can- 

 not be refused. The consequence above stated appears there- 

 fore incontestible ; but it is all that can be drawn from the expe- 

 riments. Thus, as we shall presently see, the numbers which 

 they furnish cannot be regarded as sufficiently accurate to en- 

 able us to deduce from them, in a certain and absolute manner, 

 the law of the increase of temperature in depth ; some of them 

 would make it too high, and others too low. 



As it is, however, a great step gained to be assured that there 

 is an increase, and that this increase is probably rapid, it is es- 

 sential to take in here the result of an experiment of Mr W. 

 Fox''s, which is much more important than it seems at first sight, 

 and which would have had much more interest, had not the au- 

 thor omitted to relate several circumstances wliich he had done 

 well to have made known. 



The waters which issue from most of the numerous tin and 

 copper mines of Cornwall, are led by means of various branch- 

 ings into a great adit, which conducts them above the valley of 

 Carnon, and which, at its termination, pours forth 1400 cubic 

 feet of water per minute, amounting to about 60,000 tons in the 

 day. In one of the branches leading to the great adit, the wa- 

 ter of six mines, from 900 to 960 feet deep, Mr Fox, at half a 

 mile from its mouth, found the water at 73° 4' Fahr. In a second 

 branch, leading off the water of ten mines, having a mean depth 

 of from 660 to 720 feet, the temperature was 66° 6' Fahr. at a 

 third of a mile. In a third branch, which drains seven mines, 

 whose mean depth is from 600 to 660 feet, the water marked 

 64° 9'. Lastly, the temperature of the united streams, taken at 

 the mouth of the great canal or adit, was found to be 69° 3' 

 which is 10° T cent, above the mean temperature of the coun- 

 try. In the second place, it may easily be proved, by means 

 of the data which we have already enumerated, that it is indepen- 

 dent of the influence which might, in other cases, be attribu- 

 ted to the lights and the presence of the workmen. In fact, if 

 it be admitted that the working of the mine requires the con- 

 stant employment of 2000 workmen, and 2000 lamps, burning 

 each one-half ounce of oil in the hour, it will be found, that, in 

 one hour, the heat produced by the lights and workmen will 



JULY SEPTEMBER 1828. T 



