202 TWO GLENS AND THE AGENCY OF GLACIATION. 



by a large number of perched blocks, is a granitic ridge, 700 feet above the level of 

 the sea, with a steep and partially precipitous face, facing S. and S.E. This face is 

 quite untouched, and rough — showing no trace whatever of any rounding or smoothing 

 agency having passed along it or down it. But the back of the same hill, facing to the 

 N. and N.E., is on the contrary well smoothed and glaciated. Behind and above this 

 hill there is another and a much higher ridge, also granitic, which rises to the elevation 

 of 1000 feet, and presents, like the lower one, a precipitous face, quite untouched 

 by glaciation, towards the S. and S.E. Between the two hills there is a deep hollow, over 

 which, in some parts, many huge blocks of transported stones are scattered. These blocks 

 also are often very angular and unrolled. It is impossible to reconcile any of these 

 facts wdth the agency of any body of ice large enough to rest upon, and to move along, 

 the whole surfaces of the country. They are essentially connected with the passage of 

 ice in some form which was partial and selective, impinging on all surfaces which were 

 exposed to its movement from the N. and N.E., but which admitted of its passing 

 entirely over, without any contact, all other surfaces which were not so exposed. 



The evidence, therefore, in favour of the action of floating ice in a glacial sea grounding 

 upon and grinding over the rocks and shoals of a rising and emerging land, is accumulative 

 evidence, including a great variety of corroborating details. Moreover, it is evidence 

 which, so far as I can see, is of such a nature as to exclude the possibility of the action of 

 other forms of ice, such as have been suggested in either local glaciers or in an ice sheet. 



I do not deny, nor do I seek to minimise, the great difficulties presented by this 

 explanation of a very peculiar set of facts. It involves the idea of a submergence of the 

 land, and a re-emergence of it, at some time so recent that in all its main contours or 

 outlines the country was very much as we see it now. But the difficulty of conceiving 

 such an operation, or rather the difficulty of accounting for it by any known physical 

 causes, must not lead us to hesitate in accepting evidence which in itself admits of no 

 other explanation. We have to recollect, too, that at least one other explanation, 

 namely, that of an ice sheet moving over the whole country, besides failing to account 

 for the facts, involves physical difficulties of a much more formidable nature. The 

 supposed cause of motion in such a body of ice has never been explained. I believe it to 

 be a physical impossibility. This cannot be said of the forces which we must believe 

 have acted on the elevation ol our existing islands and continents. They have been 

 undoubtedly such as are capable of reproducing like effects at any time. We are, no 

 doubt, accustomed to assume that these earth-movements have been sleeping for a far 

 longer time, and that, when they did act, they always acted with infinitesimal slowness 

 in time and in effects. But this is an assumption in which, very possibly, we may be 

 entirely mistaken ; and we have to consider the significant fact that one of the most 

 experienced and most cautious of our eminent geologists, Professor Prestvvich, has very 

 recently been led to the opinion that some comparatively sudden submergence, and some 

 correspondingly rapid re-elevation of the land, has left clear evidence of its occurrence all 

 over the south of Europe, at a date quite recent in geological time. 





