128 THE FAIRY-LAND OF SCIENCE. 
We cannot here go into the history of that great 
Glacial Period long ago, when large fields of ice cov- 
ered all the north of England; but when you read 
it for yourselves and understand the changes on the 
earth's surface which we can see being made by ice 
now, then such grand scenery as the rugged valleys 
of Wales, with large angular stone blocks scattered 
over them, will tell you a wonderful story of the ice 
of bygone times. 
And now we have touched lightly on the chief 
ways in which water and ice carve out the surface 
of the earth. We have seen that rain, rivers, springs, 
the waves of the sea, frost, and glaciers all do their 
part in chiselling out ravines and valleys, and in pro- 
ducing rugged peaks or undulating plains here cut- 
ting through rocks so as to form precipitous cliffs, 
there laying down new land to add to the flat country 
in one place grinding stones to powder, in others 
piling them up in gigantic ridges. We cannot go a 
step into the country without seeing the work of water 
around us; every little gully and ravine tells us that 
the sculpture is going on; every stream, with its bur- 
den of visible or invisible matter, reminds us that 
some earth is being taken away and carried to a new 
spot. In our little lives we see indeed but very small 
changes, but by these we learn how greater ones have 
been brought about, and how we owe the outline of 
all our beautiful scenery, with its hills and valleys, 
its mountains and plains, its cliffs and caverns, its 
quiet nooks and its grand rugged precipices, to the 
work of the " Two great sculptors, Water and Ice." 
