8 Scientific Proceedings, Boyal Dublin Society. 



bushes have been left starving on the almost bare rocks owing 

 to the subsidence of the soil into the valleys. 



It is far from my intention to make any sweeping, or general 

 application of these agencies, to account for accumulations of rocks 

 in different geological periods for which a glacial origin is gene- 

 rally claimed. My object is to draw the attention of geologists to 

 them, as their potency is, perhaps, not so fully recognized as it 

 should be. 



I do not profess to be an anti-glacialist ; but where so much 

 depends upon the fact of glacial epochs having existed during 

 different geological periods, it seems to be due to the physicists 

 that geologists should use the very utmost caution in the matter. 



Here I would refer to a case where there appears to me to be 

 fairly presumptive evidence of the existence of a glacial epoch at 

 so early a geological period as the Cambrian. Recently, at Grair- 

 loch, in Rosshire, I examined the varied traces of the operations of 

 the glacial period in that neighbourhood, and while doing so I 

 was impressed with the belief that certain Cambrian breccias lying 

 in valleys, scooped out of the surface of the Laurentian rocks, 

 afforded evidence from their position, much more than from their 

 lithological constitution, of the existence of a glacial period in 

 those early times. Modern glacial action appears to have re- 

 scooped the valleys which must have already been in existence 

 when the breccias were deposited, and therefore it may be argued 

 that they were originally carved out by the same tools. This is 

 of course not quite conclusive, as it would be if, in support of it, 

 glaciated surfaces were found underlying the Cambrians ; but 

 as yet I am not aware that any such have been discovered at 

 Gairloch. 



DESCEIPTION OF PLATE I. 



Naini Tal landslip of the 18th September, 1880, from a photograph. 



