34 Ice Maries in North Wales. [Jan., 



becoming more certain that even the grandest and most romantic 

 scenery of mountainous countries has been produced by the slow 

 but long-continued action of those natural causes which we see 

 daily at work, but whose effects during the few years that we can 

 observe them are almost imperceptible. These causes are, the ocean 

 waves, running water, rain and frost; which, if acting for long 

 periods during which subterranean forces are also at work slowly 

 elevating and depressing large tracts of country and to some extent 

 fracturing and loosening the rocky strata, seem capable of producing 

 all the chief features which the surface of the earth now presents 

 in non-volcanic regions. 



There are, however, a considerable number of very remarkable 

 phenomena which none of these causes will account for, and which 

 appear to have been overlooked or thought unimportant till about 

 twenty-five years ago, when the celebrated naturalist Agassiz visited 

 this country after having carefully studied the effects of modern 

 glaciers in the Alps. He it was who first showed that they could 

 be all explained to the minutest detail by the hypothesis of a recent 

 " glacial period," during the continuance of which the mountains 

 of "Wales, Cumberland, and Scotland were covered with perpetual 

 snow, and sent down glaciers into most of the valleys, and some- 

 times even into the sea. At first this hypothesis was received with 

 incredulity and derision, since it completely contradicted the almost 

 universal belief of scientific men that the earth had been for ages 

 cooling, and that all preceding epochs had been warmer than the 

 present one ; but it very soon worked its way even among the most 

 sceptical inquirers, till at the present day there cannot be found 

 a geologist who denies the reahty of the " glacial epoch," or the 

 correctness of that interpretation which explains many peculiar 

 features of our own mountain scenery by the agency of ice. 



A great deal has since been written by geologists and physicists 

 on the effects of ice-work, but comparatively little has been given 

 to the general public; and as the subject is at this time again 

 attracting much attention, owing to new applications of the theory 

 which have given rise to much discussion and are greatly stimu- 

 lating inquiry, and as it requires little or no previous knowledge of 

 geology to understand either its facts or its theory, I have thought 

 that a popular account of such prominent glacial phenomena as are 

 observable in all our chief mountain districts would be acceptable to 

 many readers of this periodical. 



We may conveniently consider the chief evidences of a glacial 

 period under the following heads : 1st, The drift ; 2nd, Moraines ; 

 3rd, ' Koches moutonnees ' ; 4th, Grooved and striated rocks ; 5th, 

 Boulders and perched blocks ; 6th, Alpine lakes ; — and in this order 

 I propose to record the few observations I have made during a 

 month spent near Snowdon and Cader Idris last autumn, incorpo- 



