278 M. L. Cordier on the Temperature of 



1. All the phenomena observed, being in accordance with the 

 mathematical theory of heat, announce that the interior of the 

 earth is furnished with a very elevated temperature, which is 

 peculiar to it, and which has belonged to it since the origin of 

 things ; and, on the other hand, the volume of the earth's mass 

 being infinitely greater than that of the mass of waters (about 

 ten thousand times greater)^ it is very probable that the fluid- 

 ity which the globe incontestibly possessed, before assuming its 

 spheroidal form, was owing to heat. 



2. This heat was excessive, for that which may at present 

 exist at the centre of the earth, supposing a continued increase 

 of 1 degree for every 25 metres of depth, would exceed 3500'' 

 of Wedgwood's pyrometer (upwards of 250,000° centigr.) 



3. It must be admitted that the temperature of 100° of Wedg- 

 wood's pyrometer, — a temperature capable of melting all the 

 lavas, and a great part of the other known rocks, exists at a 

 depth which is very small, compared with the diameter of the 

 earth ; and, for example, from my experiments, that this depth 

 is less than 6B leagues, of 5000 metres, at Carmeaux, 30 leagues 

 at Littry, and 23 leagues at Decise, numbers which correspond 

 to 5^, /^, and /j of the mean radius of the earth. 



4. There is, therefore, every reason to believe, that the inter- 

 nal mass of the globe is still possessed of its original fluidity, 

 and that the earth is a cooled star, which has been extinguished 

 only at its surface, as Descartes and Leibnitz thought. 



5. If there be considered, on the one hand, the extent which 

 Dolomieu's observations on the seats of volcanic foci *, and 

 our own experiments on the composition of lavas, have given to 

 volcanic phenomena -f, and, on the other, the great fusibility of 

 the matters which all the volcanoes of the globe at present throw 

 up, or even of those which they ejected long ago ; it must be 

 inferred that the internal fluidity commences, at least in many 

 points, at a depth much less than that at which the temperature 

 of 100 degrees of Wedgwood's pyrometer. 



• Dolomieu, Rapport sur ses Voyages in 1797- Journal des Mines, t. vii, 

 p. 385. 



t Recherches sur Differens Produits Volcaniques. Journal des Mines, 

 t. xxi, p. 249. and t. xxiii. p. 55. — Memoire sur la Composition des Laves de 

 tous les Ages. Jouni. de Phys. t. Ixxxiii. p. 135. 



