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Ch. XXXIX.] 



OF QUADEUPEDS. 



357 



picture ; but upon all the plain^ which, last evening was so 



teemin 



t5 



Migratory 



common 



individuals of every species slowly to extend their range in 



numbers 



migrate 

 manner 



multitude 



with famine. It may be useful to enumerate some examples of 

 these migrations^ because they may put us upon our guard 

 against attributing a high antiquity to a particular species 

 merely because it is diffused over a great space : they show 

 clearly how soon^ in a state of nature^ any species might spread 

 itself in every direction^ from a single pointy and how the 

 territory of one animal may be invaded by another^ leading 

 occasionally to the extermination of the weaker species. 



In very severe winters, great numbers of the black bears of 

 America migrate from Canada into the United States ; but in 

 milder seasons, when they have been well fed, they remain 

 and hybernate in the north, f The rein-deer, which in Scan- 

 dinavia, scarcely ever ranges to the south of the sixty-fifth 

 parallel, descends, in consequence of the greater coldness of 

 the climate, to the fiftieth degree in Chinese Tartary, and 



more 



part of England. 



In Lapland, and other high latitudes, the common squirrels, 

 whenever they are compelled, by want of provisions, to quit 

 their usual abodes, migrate in amazing numbers, and travel 

 directly forwards, allowing neither rocks nor forests, nor Lhe 



broadest waters to turn them from 



In like 



manner the small Norway rat sometimes pursues its migrations 

 in a straight line across rivers and lakes ; and Pennant informs 

 us, that when the rats, in Kamtschatka, become too numerous, 

 they gather together in the spring, and proceed in great bodies 

 westward, swimming over rivers, lakes, and arms of the sea. 

 Many are drowned or destroyed by water-fowl or fish. 



As 



■^ Expedition from Pittsburg to the 

 Eocky Moiintains, vol. ii. p. 153. 



t Eichardson's Fauna Boreali-Ame- 

 ricana, p. 16. 



