276 M. L. Cordicr on the Temperature of 



If we examine the data of this great problem, it is easy to 

 see that only one of them might lead to uncertain results. This 

 datum, which is at the same time the most direct and the most 

 decisive, is that which is grounded on the experiments from 

 which it has been inferred that the temperature of the earth 

 augments progressively from the surface toward the centre. It 

 may be asked, if these experiments are accurate, if they have 

 been suitably discussed, if they are sufficient, and if the infe- 

 rences that have been drawn from them leave nothing to be de- 

 sired ? 



I have thought that it would be useful to settle these doubts, 

 and this for the interest of science in general, more than for that 

 of an opinion which I have myself cherished for a very long time, 

 and to which I have already paid the tribute ol' my researches 

 in other points of view. Such is therefore the principal object 

 of the memoir, which I have now the honour of communicating 

 to the Society. 



M. Cordier then proceeds to a very interesting examination of 

 the various experiments on subterranean temperature, hitherto 

 published, in which he discusses all that is known in regard, 1^^, 

 To the temperature of the water, whether running or standing, 

 met with in mines ; 9.dly^ To the temperature of the air in the 

 shafts, galleries, and levels of mines ; and, Sdly^ To the tempe- 

 rature of the air in caves, as in those for instance under the Ob- 

 servatory at Paris. From these details he draws the following 

 conclusions : — 1. If we except a certain number of observations, 

 as not sufficiently satisfactory, all the others announce, in a more 

 or less positive manner, that there exists a remarkable increase 

 of temperature, proceeding from the surface of the earth towards 

 the interior. 2. The results obtained at the Observatory at 

 Paris, are the only ones from which a numerical expression of 

 the law, which this increase follows, may be deduced with cer- 

 tainty. This expression carries to twenty-eight metres, the 

 depth which corresponds to the increase of 1° of subterranean 

 heat. It results from this, that, at the depth of 2,503 metres 

 under Paris, we would reach a temperature of 212° of Fahren- 

 heit's scale. 3. A small number only of the other results fur- 

 nish numerical expressions, sufficiently near the law in question 

 to be admitted. These expressions vary from 57 to 13 metres. 



