PROPAGATION OF FISH. 237 



they often dwell where salmon cannot. Trout require a 

 temperature of water never exceeding seventy degress. 

 At sixty-eight degrees they begin to suffer ; at seventy 

 degrees, unless there is a strong and broken current to 

 give life to the water, they die rapidly, and not one 

 will survive a temperature of seventy-five degrees. It is 

 simply manifest then that the Southern and Western 

 rivers are not generally inhabitable for trout or salmon. 

 Trout may be found in the head w r aters of such as rise 

 in the Alleghany range of mountains, but salmon can 

 exist in none of them. So also with the sluggish, 

 muddy rivers of Ohio, Indiana, Illinois, Missouri and the 

 vast central region of our continent. Throughout the en- 

 tire section between the Alleghanies and Lake Superior and 

 the Northern Mississippi, except in Northern Michigan, 

 no trout are found, and then again not till you come to 

 the Rocky Mountains. Trout and salmon, except in the 

 matter of migration, are similar in their habits. The 

 eggs of either may be hatched in the same boxes, with 

 the same water, in about the same time, and under the 

 same treatment. 



When we speak of the temperature of a pond or river, 

 allowance must be made for springs to which fish will 

 have recourse, precisely as men perishing in a room for 

 air, would put their mouths to a knot hole to breathe. 

 If there are springs enough, trout will live in waters the 

 body of which reaches a higher temperature than seventy- 

 five. So also, a strong rush of water as with a cataract 

 or rapids, will enable them to endure greater heat than 

 they could otherwise stand. Still it is not safe to subject 

 any of the eastern salmon or trout family to a perma- 

 nent temperature higher than sixty-five degrees. Salmon 



