16 Experiments for ascertaining | Jan., 
than that of Grenelle, and the temperature of the water is 9:09 
Fahr. higher. 
An artesian boring in the vicinity of Geneva to a depth of 724 
feet, and at an elevation of 1,600 feet above the sea-level, showed 
the increase to heat at the rate of 1° Fahr. for every 55 feet ; while 
another at Mendorff, in Luxemburg, which penetrated to a depth 
of 2,394 feet, gave a result of 1° Fahr. for every 57 feet. This 
boring is particularly interesting and valuable, not only for its 
depth, but from the fact of its passing through several formations, 
including the Lias, Keuper, Be, Gies bigarré, and entering 
slaty rocks.* 
Some years since, Mr. R. Were Fox undertook a series of expe- 
riments on the temperature of the Cornish mines, which are reported 
in the ‘Transactions of the British Association.+ These experi- 
ments appeared to show that the increase of temperature was in a 
decreasing ratio to the depth ; but it is to be recollected that in the 
case of mines, the temperature is affected by several sources of 
error, such as ‘the spontaneous combustion of pyrites. The results, 
however, are not without value, and are as follows :— 
Atadepth of 354 feet the temperature was 60° Fahr. 
7 te) 
9 792 ” ” ” 
1,434 ,, z BOP iS 
orl 
Assuming the invariable temperature, presently to be explained 
more fully, to be 50° Fahr., the rate of increase would be arrived at 
as follows :— 
10° at 354 feet, less 50¢ = 304 feet, or 1° in 30-4 feet. 
of 10° at 438 _,, or 1° in 43°8_,, 
and of 10° at 684 ,, or 1° in 64:2, 
The observations taken in ne Tresavean mine in 1837, which 
were the deepest of the series, gave the following results :— 
At 1,572 feet from the surface the temperature was ee a Fahr. 
Atl 74 OnF ” , 
At the above depth in another lode a8 oe 50 s 
in a third lode 92-12) % 
Giving the mean temperature for a depth of i. 740 fet Oi emer 
Mr. R. Hunt, F.R.S., who has made some observations in refer- 
ence to the question of increase of temperature in mines, states that 
he has found the temperature as high as 100° at a depth of 1,920 
feet (820 fathoms) in the Tresavean mine. 
Several carefully executed experiments carried on in coal mines 
have been recorded; and amongst the earliest on which much reli- 
ance is to be placed, are those of Professor J. Phillips, F.R.S., at 
* «Cosmos. Trans. of Otté and Dallas, vol. v., p. 3-56. + Vol. ix. 
+ 50 feet from the surface is here assumed as the depth of no variation of 
temperature all the year round. 
