MIGRATION OF ANIMALS. 285 



it in a straight line or perish in the attempt ; and, if they 

 meet with a bark or other vessel, they do not alter their 

 direction, but climb up the one side of it, and descend by 

 the other. 



Frogs, immediately after their transformation from the tad- 

 pole state, leave the water, and migrate to the meadow or 

 marshy grounds in quest of insects. The number of young 

 frogs which suddenly make their appearance in the plains, 

 induced Ronduletius, and many other naturalists, to imagine 

 that they were generated in the clouds and showered down 

 upon the earth. But if, like the worthy and intelligent Dr. 

 Derham, they had examined the situation of the place with 

 regard to stagnating waters, and attended to the nature and 

 transformation of the animals, they would soon have discov 

 ered the real cause of the phenomenon. 



Of all migrating animals, particular kinds of fishes make 

 the longest journeys, and in the greatest numbers. The mul- 

 tiplication of the species, and the procuring of food, are the 

 principal motives of the migration of fishes. The salmon, a 

 fish which makes regular migrations, frequents the northern 

 regions alone. It is unknown in the Mediterranean Sea, and 

 in the rivers which fall into it both from Europe and Africa. 

 It is found in some of the rivers of Fi ance that empty them- 

 selves into the ocean. Salmons are taken in tho rirers of 

 Kamtschatka, and appear as far north as Greenland. They 

 are found in many of the rivers of the United Statei, and 

 ascend and descend the river Columbia in immense and almost 

 incredible shoals. The Indians around this river preserve 

 them in a dried state, and make them a principal article of 

 food. Salmons live both in the ocean and in fresh waters. 

 For the purpose of depositing their spawn, they quit the sea 

 in the month of September, and ascend the rivers. So strong 

 is the instinct of migrating, that they press up the rivers with 

 amazing keenness, and scarcely any obstacle is sufficient to 

 interrupt their progress. They spring, with great agility, 

 over cataracts of several feet in height. In their leaps, they 

 spring straight up with a strong, tremulous motion, and do not, 

 as has been vulgarly supposed, put their tails in their mouths. 

 When they find a place which they think proper for depos- 

 iting their eggs, the male and female unite their labors in 

 forming a convenient receptacle for the spawn in the sand, 

 which is generally about eighteen inches deep. The eggs^ 

 when not disturbed by violent floods, lie buried in the sand 

 till the spring, and they are hatched about the end of March. 



