284 MIGRATION OP ANIMALS. 



mense distances, exert the greatest feats of activity, and un- 

 dergo incredible hardships and fatigue. After acquiring a 

 store of provisions, they return to their. wonted haunts, and 

 remain inactive till their food again begins to fail. 



' There are but few quadrupeds which perform migrations, 

 and these are generally limited in their extent to different 

 parts of the same country. A few species, however, which 

 have faculties for more extensive locomotion, perform more 

 extensive migrations. Thus some of the bats of England 

 spend their winters in Italy in a torpid state ; and the seal, 

 which frequents the shores of Greenland during the summer, 

 removes at the approach of cold weather to the south, and 

 spends the winter in the neighborhood of Iceland.' 



At the approach of winter, the stag, the reindeer, and the 

 roebuck, leave the tops of the lofty mountains and come down 

 to the plains and copses. Their chief objects in these flittings 

 are food and shelter. When summer commences, they are 

 harassed with different species of winged insects, and to avoid 

 these enemies, they regain the summits of the mountains, 

 where the cold and the height of the situation protect them 

 from the attacks of the flies. In Norway, and the more north- 

 ern regions of Europe, the oxen, during the winter, migrate 

 to the shores of the sea, where they feed upon sea-plants and 

 the bones of fishes ; and Pontoppidan remarks, that the cattle 

 know by instinct when the tide retires and leaves these articles 

 of food upon the shore. In Orkney and Shetland, the sheep 

 in winter, for the same purposes, uniformly repair to the shore 

 at the ebbing of the tides. Rats, particularly those of the 

 northern regions of Europe, appear, from time to time, in such 

 myriads, that the inhabitants of Norway and Lapland imagine 

 the animals fall from heaven. The celebrated Linnaeus, who 

 paid great attention to the economy of these migrating rats, 

 remarked, that they appeared in Sweden periodically, every 

 eighteen or twenty years. When about to migrate, they leave 

 their wonted abodes, and assemble together in numbers incon- 

 ceivable. In the course of their journey, they make tracks 

 in the earth of two inches in depth ; and these tracks some- 

 times occupy a breadth of several fathoms. What is singular, 

 the rats, in their march, uniformly pursue a straight line, 

 unless they are forced to turn aside by some insurmountable 

 obstacle. If they meet with a rock, they first try to pierce 

 it, and, after discovering the attempt to be impracticable, 

 they go round it, and then resume the straight line. Even a 

 lake does not interrupt their passage ; for they either traverse 



