14 Professor Forbes nn the Geology of Auvergne. 



the sound principles which mathematical pliilosophy inculcates. 

 M. Elie de Beaumont is one of the few living geologists who 

 have considered a study of general physics and mechanical phi- 

 losophy, as a fit commencement for the prosecution of a subject 

 which should draw largely on both, and that in their more dif- 

 ficult departments. It is almost exclusively with the more in- 

 tractable problems of the higher mechanics that geology has to 

 deal ; such as the equilibrium of free heterogeneous fluids, — 

 the conditions of matter under circumstances which never can 

 exist at the surface of our globe, — the analytical theory of heat, 

 — the yet more imperfect rudiments of electro-magnetism, — the 

 action of forces upon plastic and semi-rigid materials, — the im- 

 pulsive force of fluids, and their motions at great depths ; — 

 these are but a few of the thorny paths of inquiry in which the 

 speculative geologist, who wishes to take sound philosophy along 

 with him, finds himself engaged. We should, therefore, con- 

 gratulate the science on finding men of enlarged views and great 

 acquirements, likeM.Elie de Beaumont, ready to promote a gene- 

 ral taste for such pursuits, even although the temptation to over 

 step a little the legitimate paths of mathematical investigation 

 should at first be too great to be resisted.* It may at least in- 

 duce a study of the allied sciences, when geologists themselves 

 begin to find the works of their fellow-labourers too abstruse for 

 their perusal.-[* 



That the argument about the conical surface has been carried 

 too far can hardly be doubted. The impossibility of forming 

 numerical estimates in point of fact on the cases in nature, ren- 

 ders the whole rather a display of ingenuity than a substantive 

 benefit to science. The chief conclusions of any importance, 

 namely, that the higher the angle of elevation of the cone, the 



• The reasonings of M. Elie de Beaumont have not of course failed to be 

 caricatured. I recollect to have seen in a French provincial journal the ob- 

 vious truth, that, as we proceed from the apex of the imaginary fissured cone 

 . towards its base, the surn, of the incomplete spaces will diminish, proved by 

 the aid of the differential calculus ! 



•t At the very time that this paper was being read, I had the satisfaction of 

 receiving a very remarkable physico-mathematical paper, by Mr Hopkins of 

 Cambridge, upon what may justly be termed the Dynamics of Geology. It 

 is now published in the Cambridge Transactions, and an abstract in the Philo- 

 sophical Magazine. 



