GENERATION OF EELS. 193 



that they continue to find their way, in im- 

 mense numbers, to Loch Erne. The same 

 thing happens at the fall of the Bann, 

 and Loch Neagh is thus peopled by them : 

 even the mighty Fall of ShafFausen does not 

 prevent them from making their way to the 

 Lake of Constance, where I have seen many 

 very large eels. 



Phys. — You have shown that some eels 

 come from the sea, but I do not think the 

 facts prove that all eels are derived from 

 that source. 



Hal. — Pardon me — I have not concluded. 

 There are eels in the Lake of Neufchatel, 

 which communicates by a stream with the 

 Rhine; but there are none in the Lake of 

 Geneva, because the Rhone makes a subter- 

 raneous fall below Geneva ; and though small 

 eels can pass by moss or mount rocks, they 

 cannot penetrate limestone rocks, or move 

 against a rapid descending current of water, 

 passing, as it were, through a pipe. Again : 

 no eels mount the Danube from the Black 

 Sea; and there are none found in the great 

 extent of lakes, swamps and rivers commu- 



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