THE TWO GREAT SCULPTORS. \ 2 J 
clear and pure. A mile and a half of land has been 
formed at the head of the lake since the time of the 
Romans by the mud thus brought down from the 
mountains. 
Thus we see that ice, like water, is always busy 
carving out the surface of the earth, and sending down 
material to make new land elsewhere. We know that 
in past ages the glaciers were much larger than they 
are in our time ; for we find traces of them over large 
parts of Switzerland where glaciers do not now exist, 
and huge blocks which could only have been carried 
by ice, and which are called " erratic blocks," some of 
them as big as cottages, have been left scattered over 
all the northern part of Europe. These blocks were 
a great puzzle to scientific men till, in 1840, Professor 
Agassiz showed that they must have been brought by 
ice all the way from Norway and Russia. 
In those ancient days, there were even glaciers in 
England; for in Cumberland and in Wales you may 
see their work, in scratched and rounded rocks, and 
the moraines they have left. Llanberis Pass, so fa- 
mous for its beauty, is covered with ice-scratches, and 
blocks are scattered all over the sides of the valley. 
There is one block high up on the right-hand slope 
of the valley, as you enter from the Beddgelert side, 
which is exactly poised upon another block, so that 
it rocks to and fro. It must have been left thus bal- 
anced when the ice melted round it. You may easily 
see that these blocks were carried by ice, and not 
by water, because their edges are sharp, whereas, if 
they had been rolled in water, they would have been 
snioothed down. 
