360 PHILOSOPHY OF ZOOLOGY. 



gwiniad anil the grayling were no longer to be found in 

 the lakes. Higher up still, or about ^000 feet below the 

 line of {lerpetual snow, the char had disappeared ; and be- 

 yond this boundary all fishing ceased *. 



When a salt-water fish is put into fresh- water, its motions 

 speedily become irregular, its respiration appears to be af- 

 fected, and unless released it soon dies. The same conse- 

 quences follow when a fresh-water fish is suddenly immers- 

 ed in salt-water. But in what manner they are influenced 

 by the change, has never been satisfactorily determined. 



There are not a few fish which may be said to be amphi- 

 bums, or capable of living either in fresh or salt water at 

 pleasure. Such fish, in an economical point of view, are 

 extremely valuable, as they furnish to the inhabitants of 

 this and other covm tries an immense supply of food. The 

 salmon may be given as an instance in this country, where, 

 Irom one river (Tay), 50,000 head of full sized fish have 

 been procured in one season. To the Greenlanders, their 

 Angmarsaet, or Salmo nrcticus, is perhaps more valuable, 

 as it is dried hard, then broken and pounded, and formed 

 into bread, as well as consumed in a fresh or salted state. 



All these fishes seem to reside chiefly in the sea. There 

 they grow and fatten ; but when the time of spawning ap- 

 proaches, they forsake the salt-water, and return to rivers 

 and lakes. But this desertion of the ocean is only tempo- 

 rary, and regulated by the circumstances connected with 

 reproduction. The instant the spawning is finished, they 

 repair again with equal rapidity to the ocean, to repair their 

 exhausted strength, and fit them for obeying the laws of 

 their existence. Some of these fishes appear to be capable 



• See appendix to the 2d vol. of the^" Lachesis Lapponica" of Linn«u=, 

 by Sir J. E. Smith. London, 1811. 



