Temperature of the Terrestrial Globe. 13 



These experiments were made at different points of the ocean, 

 from lat. N. 7° 20' to 45° 35' lat. S. and in an extent of Ion. from 

 15° 17' to 196° r. If we compare analogous experiments made in 

 deep lakes, by de Saussure the elder, and de la Beche in the Alpine 

 lakes, by Georgi, Pallas and Gmelin in those of Siberia, by Schaw 

 and Makenzie in western America, we shall find the same results, 

 but upon a smaller scale ; the temperatures of the bottom, have been 

 constantly found lower than those of the surface. The experiments 

 of M . de la Beche, in the lake of Geneva, at different depths,* prove 

 besides, that as in the ocean, the temperatures diminish at first rapid- 

 ly and afterwards slowly* ' 



If we unite all the experiments made in so many lakes, and in coun- 

 tries so distant from each other, and if we compare them with the 

 experiments no less numerous made in the sea, in so many latitudes 

 and longitudes, we shall be justified in concluding that we have dis- 

 covered a natural law, which is that, the temperature, in the great 

 masses of water, diminishes from above downwards, at first rapidly, 

 then very slowly.f Now, is not this well established theorem, in 

 direct contradiction to the hypothesis of an interior globe of matter, 

 whose incandescent heat is the source of the mean heat of the earth 

 at its surface ? This is what we are about to examine. 



Let C, be the centre of the earth, ac the level of the ocean, bd the 

 mean level of the continents, ef the mean level of the bottom of the 

 sea, gh the level of incandescent heat. It is certain that at the con- 

 tiguous surfaces of land and water the temperature will be the same. 

 Let us endeavor to find, in the hypothesis of a central incandescent 

 globe, what this temperature would be. The mean increase of heat 

 has been admitted, in this hypothesis to be one degree C. for each 

 depth of thirty meters, La Place has estimated the depth of the 

 ocean to be at least six thousand fathoms. My geological system, 

 founded on my theory of volcanoes, presents the same data as a min- 



* See Bib. Univ. tome xii. (1819,) p. 119. 



t If the temperature of the interior, arose from any warm medium situated at the 

 exterior, and if the diminution towards the bottom, was solely the chemical progress 

 of caloric in this exterior medium, the progression of diminution would be much 

 more rapid, and M. Lenz and the other navigators, would have found perhaps even at 

 100 fathoms depth, the temperature of zero of our thermometer. This heat of the 

 ocean and lakes, proceed from the action of the solar rays, which penetrate the water 

 and thus produce heat as far as the lowest depths to which these rays penetrate ; 

 thence the decrease of temperature slackens. 



