DESTKUCTION OF AQUATIC ANIMALS. 107 



most nearly corresponding European species, and tliis is probably 

 due less to specific difference than to the fact that even in the 

 parts of the New World which have been longest cultivated, 

 wild nature is not yet tamed down to the character it has assumed 

 in the Old, and which it will acquire in America also when her 

 civihzation shall be as ancient as is now that of Europe.* 



Man has, hitherto, hardly anywhere produced such chmatic or 

 other changes as would suffice of themselves totally to banish the 

 wild inhabitants of the dry land, and the disappearance of the na- 

 tive birds and quadrupeds from particular locaKties is to be as- 

 cribed quite as much to his direct persecutions as to the want of 

 forest shelter, of appropriate food, or of other conditions indis- 

 pensable to their existence. But almost all the processes of agri- 

 culture, and of mechanical and chemical industry, are fatally de- 

 structive to aquatic animals within reach of their influence. 

 When, in consequence of clearing the woods, the changes al- 

 ready described as thereby produced in the beds and currents of 

 rivers are in progress, the spawning grounds of fish are exposed 

 from year to year to a succession of mechanical disturbances ; the 

 temperature of the water is higher in summer, lower in winter, 

 than when it was shaded and protected by wood ; the smaller or- 

 ganisms, which formed the sustenance of the young fry, disap- 

 pear or are reduced in numbers, and new enemies are added to 

 the old foes that preyed upon them ; the increased turbidness of 

 the water in the annual inundations chokes the fish ; and, finally, 

 the quickened velocity of its current sweeps them down into the 

 larger rivers or into the sea, before they are yet strong enough to 



* It is possible that time may modify the habits of the fresh-water fish of 

 the North American States, and accommodate them to the new physical con- 

 ditions of their native waters. Hence it may be hoped that nature, even un- 

 aided by art, will do something towards restoring the ancient plenty of our 

 lakes and rivers. The decrease of our fresh-water fish can not be ascribed 

 alone to exhaustion by fishing, for in the waters of the valleys and flanks of 

 the Alps, which have been inhabited and fished ten times as long by a denser 

 population, fish are still very abundant, and they thrive and multiply under 

 circumstances where no American species could live at all. On the southern 

 slope of those mountains, trout are caught in great numbers, in the swift 

 streams which rush from the glaciers, where the water is of icy coldness and 

 so turbid, from particles of fine-ground rock, that you can not see an inch. 

 l)elow the surface. The glacier streams of Switzerland, however, are less 

 ^abundant in fish. 



