The Interior of the Earth 



The Exposition du systdme du monde appeared 

 in 1795, and the Mecanique ctleste was published 

 from 1799 to 1825, barely at the dawn of experi- 

 mental science. Since then the development of 

 geology and physics has been marvellous. If 

 they supply few new arguments they at least 

 enable us to weigh more accurately the old 

 ones and to reach, if not certitude, a high degree 

 of probability. However, we must not allow 

 ourselves to be confused by the theoretical 

 speculations of which science, and especially 

 English science, is full. We must not be disturbed 

 by deservedly famous names nor by the rigour of 

 mathematical reasoning. That Darwin and Lord 

 Kelvin, by postulating an incompressible central 

 fluid, surrounded by an elastic envelope, or that 

 Hopkinson, by depriving this internal fluid of 

 viscosity, should have reached conclusions in- 

 compatible with Laplace's theory, proves nothing 

 beyond the inaccuracy of the initial hypotheses. 

 These speculations have not revealed the truth, 

 nor could they have done so. To know it we 

 must examine Nature directly, classify and analyse 

 known facts, and draw the inductions which ap- 

 pear most probable in the present state of science, 

 G 117 



