110 
POPULAR SCIENCE REVIEW. 
In some instances these can be divided into — 
I. Those due to glaciers and coast-ice, whilst the land was 
greatly elevated (1 to 4). 
II. Those due to the sea and icebergs whilst the land was 
greatly depressed (5, 6). 
But many of them are so altered and reconstructed that it is 
exceedingly difficult to attribute them to one or other of these 
divisions. What evidences, then, have we to-day ? 
“ The general surface of a great part of the British Islands,” 
says Mr. James Greikie , 66 excluding the centre and south of Eng- 
land, has a smoothed contour, which is now generally recognized 
as the work of land-ice. 
“ Hills, valleys, and knolls of rock have been ground down 
and have received that characteristic flowing outline which ice 
alone, of all natural agencies, can produce ( roches moutonnees ). 
When, moreover, we strip off the superficial cover of detritus 
and examine the surface of rock underneath, we find it covered 
with the well-known grooving and striation such as are met with 
by the side of every modern glacier in the Alps. 
66 These markings are not disposed at random, but run in more 
or less parallel lines. And when we. examine them over the 
Fig. l. 
SECTION AT EAST END OF NEIDFATH TUNNED, PEEBLES. 
a, Silurian rocks ; b, till, showing arrangement of stones on the lee side of the 
rock ; c, gravel in a hollow under the till. The arrow indicates the direction 
in which the till has travelled. 
length and breadth of the country, we discover that they point 
away outwards in every direction from the main masses of high 
ground, indicating that the ice which produced them covered 
the land in a deep continuous sheet, like that of Greenland, and 
that it moved outward and downward from the high grounds to 
the sea. So vast was the mass of ice that it swept over con- 
siderable hills, smoothing and striating their sides and summits.”* 
To this period Professor Ramsay refers the general erosion of 
the present lake-basins of Britain. 
Geikie, u Great Ice Age. 1 
