SEVENTH DAY.] MIGRATION OF EELS. 197 



fatten and thrive there. As to the instinct, which 

 leads young eels to seek fresh water, it is difficult to 

 reason: probably they prefer warmth; and, swimming 

 at the surface in the early summer, find the lighter 

 water warmer, and likewise containing more insects, 

 and so pursue the courses of fresh water, as the 

 waters from the land, at this season, become warmer 

 than those of the sea. Mr. J. Couch (Lin. Trans, 

 t. xiv. p. 70) says, that the little eels, according to his 

 observation, are produced within reach of the tide, 

 and climb round falls to reach fresh water from the 

 sea. T have sometimes seen them, in spring, 

 swimming in immense shoals in the Atlantic, in 

 Mount's Bay, making their way to the mouths of 

 small brooks and rivers. When the cold water from 

 the autumnal floods begins to swell the rivers, this 

 fish tries to return to the sea; but numbers of the 

 smaller ones hide themselves during the winter in 

 the mud, and many of them form, as it were, 

 masses together. Yarious authors have recorded the 

 migration of eels in a singular way, such as Dr. 

 Plot, who, in his History of Staffordshire, says, that 

 they pass in the night, across meadows, from one 

 pond to another ; and Mr. Arderon (in Trans. Royal 

 Soc.) gives a distinct account of small eels rising up 

 the flood-gates and posts of the water-works of the 

 city of Norwich; and they made their way to the 

 water above, though the boards were smooth planed 



