ORDER RODENTIA. 115 



devastations equal to those caused by an army of locusts. 

 These migrations of the Lemming seldom happen oftener 

 than once in ten years, and in some districts still less fre- 

 quently, and are supposed to arise from an unusual multi- 

 plication of the animals in the mountainous parts they in- 

 habit, together with a defect of food ; and perhaps, a kind 

 of instinctive prescience of unfavourable seasons ; and it is 

 observable that their chief migrations are made in the au- 

 tumn of such years as are followed by a very severe winter. 

 The inclination, or instinctive faculty which induces them, 

 with one consent, to assemble from a whole region, collect 

 themselves into an army, and descend from the mountains 

 into the neighbouring plains in the form of a firm phalanx, 

 moving on in a straight line, resolutely surmounting every 

 obstacle, and undismayed by every danger, cannot be con- 

 templated without astonishment. All who have written on 

 the subject agree that they proceed in a direct course, so 

 that the ground along which they have passed appears at a 

 distance as if it had been ploughed ; the grass being de- 

 voured to the very roots in numerous stripes or parallel 

 paths, of one or two spans broad, and at the distance of 

 some ells from each other. This army of mice move chiefly 

 by night, or early in the morning, devouring the herbage 

 as it passes in such a manner that the surface appears as 

 if burnt. No obstacles which they happen to meet in their 

 way have any effect in altering their route ; neither fires, 

 nordeep ravines, nor torrents, nor marshes, nor lakes ; they 

 proceed obstinately in a straight line, and hence it happens 

 that many thousands perish in the waters, and are found 

 dead by the shores. If a rick of hay or corn occurs in their 

 passage, they eat through it ; but if rocks intervene, which 

 they cannot pass, they go round, and then resume their 

 former straight direction. If disturbed or pursued while 

 swimming over a lake, and their phalanx separated by oars 

 or poles, they will not recede, but keep swimming directly 



