74 SCIENCE FROM AN EASY CHAIR 



and reach higher waters, like Japanese soldiers at a fort. 

 I found them (so long ago that I hesitate to name the date 

 it was a year of cholera in London, followed by a great 

 war) in a little rivulet which comes down the cliff at 

 Ecclesbourne, near Hastings, close to a cottage frequented 

 at that time by Douglas Jerrold. They were wriggling 

 up in the damp grass and overflow of the driblet 1 50 feet 

 above the shore, a stone's throw below. They must have 

 come out of the sea, attracted by the tiny thread of fresh 

 water entering it at this spot. 



The Danube and its tributary streams contain no eels, 

 although the rivers which open into the Mediterranean 

 are well stocked with them. This is supposed to be due 

 to the fact that the Black Sea does not afford a suitable 

 breeding-ground, and that the way through the Dardanelles 

 is closed to eels by some natural law, as it has been to 

 warships by treaty. Probably, however, it will be found 

 that the geological changes in the area of sea and land 

 are intimately connected with the migrations of the eel, 

 and that the eel is originally a marine fish which did not 

 in remote ages travel far from the deep waters. Its 

 gradually acquired habit of running up fresh waters to 

 feed has led it step by step into a frequentation of certain 

 rivers which have become (by changes of land and sea) 

 inconveniently remote from its ancestral haunts. An 

 interesting question is whether at the not very distant 

 period when there was continuous land joining England 

 to France and the Thames and the Rhine had a common 

 mouth opening into the North Sea, eels existed in the 

 area drained by those two rivers; and, if so, by what 

 route did they pass as silver eels to the deep sea, and 

 by what route did the new generations of young eels 

 hatched in the deep sea travel to the Thames and Rhine. 

 It seems most probable that in those days there were no 

 eels in the Thames and other North Sea rivers. 



