MAY 141 



succumb to a longer passage, although through less 

 impurity. It is true that from Teddington to Thames 

 Haven is about three times further than from Ryton to 

 Tynemouth, but there is material for reassurance even 

 upon that point. The smelt (Osmerus eperlanus) is a 

 true salmonoid, most nearly related to the grayling, ex- 

 clusively estuarine in its habit. Its limits of seasonal 

 migration are the highest point of the tide on one 

 hand, where it deposits its spawn, and the lower reaches 

 of the estuary on the other, whither it descends in 

 autumn and winter. For more than half a century it 

 has been unknown to frequent the Thames; doubtless 

 in the bad old days of indiscriminate filth the waters of 

 the estuary were uninhabitable by such a delicate fish. 

 It disappeared : even the more robust eel could not get 

 down to the sea to spawn, nor its myriad progeny of 

 elvers return through the foul water. The continued 

 presence in the Thames of eels, which must be hatched 

 in the sea, can only be explained by the communication 

 afforded by the Severn canal into the Bristol channel. 

 In 1896, however, smelts appeared in numbers in the 

 Thames, and were caught as high as Teddington, 

 whence it appears plain that if the smelt is able to 

 reside and thrive in the tidal waters, salmon may pass 

 through them uninjured in their annual migration. It 

 may be asked, Why not leave it to the salmon to find 

 their way back to the Thames as the smelts have done ? 

 The answer is that there are no rivers now frequented 

 by salmon within a great distance of the mouth of the 

 Thames, although smelts have never ceased to inhabit 



