the Interior of the Earth. 2fl9 



which it could not have escaped, namely, the comparison of the 

 masses of water and of earthy and metallic matters, m hich en- 

 ter into th^ composition of the globe. It is easy to shew that 

 the weight of the mass of water does not exceed the fifty-thou- 

 sandth part of the weight of the whole globe. Now, with what- 

 ever solvent this mass has been quickened, it is inadmissible 

 that one kilogramme of water could ever have dissolved 50,000 

 kilogrammes of earthy and metallic matters. 



We may be permitted again to remark, that it is not the spi- 

 rit of system by which we are now led to the idea of central fire ; 

 it is in spite of such a spirit, and in opposition to many prejudices. 

 This return to a former opinion is occasioned by an accurate and 

 profound examination of phenomena of very different orders. 

 It cannot be believed that by mere chance natural philosophy, 

 astronomy, and geology have arrived at the same point, after fol- 

 lowing such different paths. We may therefore affirm, without 

 fear of being considered hasty, that the hypothesis which is 

 equally a desideratum in all these sciences, seems already to pre- 

 sent the characters of a real and fundamental principle; and every 

 thing seems to predict, that it will have as powerful an influence 

 upon the progress of the theory of the earth, as that which the 

 great principle of gravitation has exercised upon the theory of 

 the motion of the celestial bodies. 



From the present state of this discussion, it would seem that 

 the Academy ought no longer to remain neutral on so important 

 a question. Perhaps it may now be time to carry into effect 

 a measure proposed at the sitting of the 28th November 

 1825, on the recommendation of M. de La Place *. Perhaps, 

 also, it would be proper to direct the attention of scientific men, 

 in general, to the subject, by offering prizes for the successful 

 discussion of some of the elements of this great question. 



The determination of the figure of the earth has occupied the 

 Academy for upwards of a century ; the investigation of the prin- 



• The measure in question was the naming a commission of six members 

 (MM.;de la Place, Arago, Poisson, Thenard, Gay Lussac, and Dulong), who 

 were directed to make out a programme of experiments to be performed, that 

 the Academy might be enabled to determine, by correct experiments, \sty The 

 state of the earth's magnetism ; 2rf/y, The pressure and composition of the at- 

 mosphere ; 3rf/y, The heat of the globe at different depths. 



