93 



west valleys, it is quite manifest that no force of water could have 

 hurled them to this position, their detached nature seeming singu- 

 larly to favour the hypothesis, that tliey were carried thither by a 

 large mass of floating ice, which, on uielting, left them as an isolated 

 group in this remote valley, then probably a bay or frith of an 

 arctic sea. 



Glacial Theories. — The glacial theory, as at first propounded, has 

 now, I apprehend, very few supporters, but to any such I recom- 

 mend the perusal of the theoretical investigation of Mr. Hopkins, 

 'On the Motion of Glaciers;' for he has shown, by clear mathe- 

 matical analysis, that the locomotion of such bodies over large and 

 flat continents is a theory founded in mechanical error, and invol- 

 ving conclusions irreconcilable with the deductions of collateral 

 branches of physical science. 



Having occupied so much of your time last year with observa- 

 tions on the theories respecting the action of ice under both terres- 

 ti'ial and marine conditions, and having then so fully expressed 

 my opinions on the impractical^ility of explaining the transport 

 of erratic blocks to great distances, except by the medium of 

 floating ice, I shall no longer enter into the list of disputants 

 upon a question which must be long studied, and viewed under 

 various aspects, before good and firm conclusions can be separated 

 from those which are loose and dangerous. I must, therefore, 

 content myself with referring you to the additional communica- 

 tions of M. Agassiz to the Institute of France, and to the writings 

 of Professor James Forbes*. The new views of the subject which 

 are introduced by so profound a mathematician as ?»Ir. Forbes, lie 

 rather beyond the compass of the practical geologist, and lead into 

 the domain of pure physics. As geologists, however, you must not 

 omit to consult that excellent work on the Glaciers of the Alps, by 

 our eminent foreign associate M. Charpentier, of the existence of 

 which I very much regret to have been ignorant when I last ad- 

 dressed you ; for to whatever extent we may be led to agree with or 

 dissent from his theories, it is quite manifest that they are founded on 

 patient and very long-continued observation of facts. Nor will you 

 pass over the ingenious views of M. Hugi, long known as an Alpine 

 geologist ; and you will sift the value of the evidences on which he 

 grounds his rejection of the views of Professor Agassiz. This subject 

 is now, indeed, so extended, that witliout revisiting the Alps or some 

 active centre of glacial action, it would be presumptuous to advance 

 any further opinions of my own. 



Ready as I have always been to admit the transport of blocks in 

 ice from any former seat of congelation, and particularly in tracts 

 where marine shells of arctic characters are associated with the 

 surrounding drift, 1 am here, however, bound in candour to state, that 

 in my desire to see established as a fundamental point of reasoning, 

 " the submarine condition of by far the largest parts of the surface 

 of Northern Europe when erratics were distributed," I have been 



* Edinburgh Phil. Journal, 1842. 



