AND OF THE OTHER BODIES OF SPACE. 23 



other things in proportion, and these densities becoming much 

 greater at greater depths ; so that the entire mass of a cool 

 globe should be of a gravity infinitely exceeding five and a 

 half times the weight of water. From these considerations 

 arose the hypothesis of a central heat, causing an expansion of 

 the materials. This is now, however, losing favour, in conse- 

 quence of experiments which show that substances cannot be 

 maintained at a high, while in contact with similar substances 

 at a lower temperature. 1 It is now thought that electric cur- 

 rents will yet account for the high temperature of the interior. 

 While the matter remains undetermined, it may be pointed to 

 as one tending to support the Laplacian cosmogony ; the 

 statical fact alone, which is not questioned, appears in remark- 

 able harmony therewith, in as far as it proves a rarity of ma- 

 terials in the interior. 



1 The researches on this subject were chiefly conducted by the late 

 Baron Fourier, Perpetual Secretary of the Academy of Sciences of 

 Paris. See his Theorie Analytique de la CJialeur, 1822. 



