Pram Srarrs For Suorr Riszs. 415 
These stairs, of heavy timbers and mason-work, are intend- 
ed to assist salmon and trout up small natural falls or dams, 
and for such object are highly successful. A dam may be 
necessary across the stream a few rods below, so as to deepen 
the water below the fall, and give the fish a swimming start. 
The height of this sub-dam should be three feet, and the 
whole work well considered, and designed with much atten- 
tion to the gradient, depth of water, and place for the foot of 
the ladder. 
The most important American ladder is the one adopted 
by the Dominion of Canada, a sketch of which will be found 
on the following page. 
