INTRODUCTION. 7^ 



but it is, perhaps, requisite for this purpose, that 

 the sea be not too deep for them ; and the sugges- 

 tion, accordingly, of Mr. Pennant and others, that 

 some fishes, which are destined at certain seasons 

 to migrate, are, at other times, buried in the vast 

 profundity of the seas, is not a very probable one ; 

 at least, we know, that the greater number of 

 fishes congregate principally in shallow waters, and 

 about coasts ; and that, when farther from the 

 shore, it is chiefly over sand- banks, such as those 

 of Newfoundland and the Dogger-bank, that they 

 are met with. Is it conceivable that the herring, 

 for example, should exist unscathed, as has been 

 supposed, under a pressure of 683 fathoms of water, 

 which has been proved to be the depth of some 

 parts of the sea between Iceland and the north of 

 Norway ; or under that of more than 780 fathoms, 

 to which depth the water, a little further north, has 

 been sounded, without finding a bottom ? Whe- 

 ther the animal could ever reach these depths, by 

 the most energetic efforts, may be very reasonably 

 questioned ; but that it could long hold its station 

 there, and that in full possession of all its functions, 

 appears to be most improbable. We shall now 

 proceed to the manner and the organs by which 

 fishes move through their native element, or 



