254 THE FOREST LANDS OF FINLAND. 
flow follows, with increased effect; by a continuation of 
the process, a cut is sawn, as it were, in the retaining bank 
with still increasing effects. And as the process goes on, 
the sides of the channel, which is being formed, are under- 
mined and fall, and the material is swept away by the 
flow. The erosive power of water is weak, but the erosive 
power of water charged with solid material is great; and 
proportioned to this are the effects seen. Water will do 
little to polish granite, but water and sand will do it; 
sweet oil will do little to polish steel, but sweet oil charged 
with emery, or even with rotten-stone, is all-powerful ; the 
wind can do little to polish glass or garnet, but sea-sand, 
borne onward by the wind, tells upon the hardest rocks, 
and will polish both glass and gems. And so is it with 
the water charged with mud, and sand, and gravel, and 
stones. The sides of the rocky bed of a rapid are under- 
mined and fall; and the swirl of stone-laden water at the 
foot of a waterfall dashes the force it has obtained against 
the rock over which it has poured, and undermines and 
brings down this as well as the confining walls of rock at 
the sides of the current. At the Falls of Niagara may be 
seen what may thus be done. Over these Falls pours all 
the water coming from Lake Superior, Lake Michigan, 
Lake Huron, and Lake Erie, to Lake Ontaria. The cataract 
is said to have receded 50 yards since the commencement 
of the present century. Below the Falls the river flows in 
a channel which has been thus formed. It extends for 
‘miles, is 150 feet deep, and 160 yards, or well nigh 500 
feet, wide, and the process is still going on. A remarkable 
occurrence in connection with this, which occurred within 
the last five-and-twenty years, was the fall of Table Rock. 
Of this a contributor to the Philadelphia Bulletin wrote : 
‘I said I had something to do with the fall of Table 
Rock, that broad shell on the Canada side, which in 1850 
looked over the very cauldron of seething waters, but which 
tumbled in to it on a certain day in the month of June of 
that, by me, well remembered year. About noon on that 
day I accompanied a lady from the Clifton House to the 
