NATURAL HiSTOilY. 



Of beasts the bearer plods his task, 

 While the sleek tigers roll and bask, 

 Nor yet the shades arouse." SMART. 



hawks, and weasels, so that but a small proportion of their number survive the perils 

 of their journey. In some instances they have been observed, after a lapse of time, 

 to return to their native mountains. Sometimes the females have borne young 

 during their migration, and have been seen carefully carrying them on their backs. 

 After crossing a sfcream, or an arm of the sea, upon landing on the opposite bank 

 they halt to sun and dry themselves, and after feeding again proceed upon their 

 journey. 



It was once believed that these animals fell from the clouds at particular seasons ; 

 and some persons positively affirmed that they had seen a lemming fall from the 

 skies a not improbable occurrence, when it is remembered that birds of prey follow 

 these troops on their journey, and, swooping down upon them, carry into the air as 

 many as their talons can seize. One of these escaping, and falling to the earth, 

 would at once give rise to the above misconception. An eye witness once stood for 

 two hours watching a multitude of lemmings pasting by. 



375. Why have beavers remarkably broad and thin tails? 



Because they spend th 

 greater part of their time in 

 the water, and pursue a 

 busy life by the side of 

 streams, and in the small 

 mounds or islands formed 

 by meandering waters. To 

 guide their movements in 

 the variable eddies and cur- 

 rents which they have to 

 meet, they require a power- 

 fill rudder; and this is 

 furnished by their broad, flat, and scaly tails. 



376. The formation of their tails is the more remarkable, because, while their 

 bodies are covered with fur so fine that it constitutes a valuable article of commerce, 

 their flattened tails are not endowed with fur, but have scaly surfaces, which render 

 their action upon the water most efficient. (See 377.) 



377. Why are the incisor teeth of beavers remarkably 

 developed ? 



Because they require the branches and trunks of trees in the 

 construction of their houses, and these natural implements are 

 necessary to assist them in felling the timber. These teeth are 

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