THE SALMON. 97 
trout and salmon ; there are certain prerequisites to the 
continuance of the species that must be complied with. 
The fish must ascend to the fresh water to spawn, and if 
prevented by an improperly constructed dam, will quit 
the locality never to return. 
It should be known that, contrary to the usually 
received opinion, salmon cannot surmount a fall of much 
over ten feet ; this, probably, is the full extent of their 
powers. And in effecting this, much depends upon the 
depth of water at its foot ; the deeper it is the higher 
they can leap. They do not take their tails in their 
mouths, according to the ancient theory, to enable them 
to spring higher, but rush with their utmost velocity 
from the bottom, and are carried by their momentum a 
considerable distance out of water. Such a leap or a 
struggle against strong rapids weakens them, and they 
must soon rest to recover strength for another ascent. 
They thus congregate below each fall, and often make 
many efforts before they overcome it. They usually 
move at night or early in the morning. A dam of fif- 
teen or twenty feet w^ill effectually exclude them from 
any stream, but may be rendered innocuous at small 
expense by placing below the wasteway boxes of heavy 
wood, with a fall of not over five feet from one to the 
other. A salmon leaps from the river to the first, from 
that to the next, and so on till he has overcome the 
barrier. A broad sluiceway leading at a moderate 
angle to the pool below, will probably answer as well. 
The fish, as they enter the rivers, may be deterred 
from entering, or all captured in nets spread entirelj' 
across the month, and when those that do pass have 
5 
