152 DE. J. MOEISON ICE AIJ^D ITS "WORK. 



its upper surface to be seen from the mast-head. This upper 

 surface lloss describes as a smooth plain, shining like frosted silver, 

 and stretching away as far as eye could reach into the illimitable 

 distance. This ice-cliff is doubtless the terminal front of the 

 immense Antarctic ice-cap which covers the South Polar Conti- 

 nent, and is pushed northwards over the sea-bottom in the same 

 manner as we have seen are the glaciers of Greenland, imtil it 

 reaches depths where the pressure of the water underneath it 

 becomes powerful enough to break off large segments from its 

 extremity, and so stop its further progress. These great segments 

 float away as icebergs, which in the Antarctic seas attain gigantic 

 proportions. Some of the Antarctic icebergs are no less than 

 2,000 feet in depth, and attain a length of several miles. The 

 South Polar land seems to be completely buried under an enormous 

 thickness of ice, the depth of which, • within the Antarctic circle, 

 has been estimated to be at least two miles. 



There is very strong evidence to show that all our mountain- 

 valleys in England, Wales, Scotland, and Ireland, were filled at a 

 date geologically-speaking comparatively recent, by great glaciers 

 similar in all particulars to those which exist at the present day in 

 Switzerland and Norway. Geologists also generally believe that 

 at a date generally estimated at from 100,000 to 200,000 years 

 ago, the whole country north of about the latitude of London was 

 covered for a lengthened period by an enormous ice-cap comparable 

 to that which we find in Greenland, or even to that mighty ac- 

 cumulation of ice which buries deep the whole Antarctic Continent. 



Let us consider the evidence for the former existence of glaciers 

 in this country. We find moraines in all our mountain-valleys, — 

 mounds of rubbish running across the valleys in a more or less 

 perfect condition, containing scratched stones. In every long 

 mountain-valley we find several moraines, or their remains, marking 

 the terminal limits of the glacier at various stages of its existence. 

 We also find morainic matter on the sides of the valleys, — the 

 remains of the lateral moraines. On the sides of the hills enclosing 

 the valleys we also find abundance of true perched blocks which 

 have evidently been deposited there by ice ; and we find the 

 rocks in various places scored and striated, as well as rounded and 

 polished. The projecting bosses of rock are smoothed and rounded 

 on the side which looks up the valley, while the other side may 

 retain its original roughness. The floors of the valleys are covered 

 by a layer of tenacious clay filled with stones, which is a remnant 

 of the moraine profonde of the old glacier. 



We find also other appearances which ice filling up the valleys 

 is insufiicicnt to account for. The tops of the mountains are more 

 or less rounded and smoothed, and we have glacial markings and 

 strioe at great heights. This is universal in the mountains of 

 Scotland, Wales, the North of England, and Ireland. We con- 

 clude, therefore, that all these districts were once covered by one 

 great ice-cap or more, which levelled up the valleys and covered 

 the mountain-tops in the same manner as the great ice-sheet of 



