the Residence of certain Fishes. 213 
about three acres, was so frozen over as to admit of skating. As 
to their quality, it was considered by the fishermen of the Tees, 
by whom the pond was drawn, that they had never seen “a finer 
lot of Smelts ;” so that in this case there was no loss of flavour or 
qua ity. 
The common pike, Esox Lucius, which is an inhabitant of fresh 
lakes with us, is also found in the Caspian sea; proving that this 
animal among others is indifferent to the quality of the water which it 
inhabits, and, in this case, permanently so. 
It seems to be unquestionable, that in the Dee and some other 
Scottish rivers, the common eel, Murena Anguilla, migrates an- 
nually to the sea, wherever it has the power of reaching it ; return- 
ing again to the rivers and lakes which it has generally been sup- 
posed permanently to inhabit. The conger eel, Mureena Conger, 
which is an inhabitant of the sea, in general, also frequents rivers ; 
so that, of this genus, there are two at least of which the ence 
is occasionally convertible. 
The Gadus Callarias, or torsk, is also known to enter the mouths 
of rivers, so that it can reside at least for a time in fresh waters 
without injury; but it is not known to remain in them permanently. 
That the Gadus Morhua, or common cod, can reside permanently 
in fresh water, is proved in Shetland. In the mainland, as it is 
termed, of that group, the inlet called Stromness-voe communicates 
with an inland fresh-water lake by a channel so narrow as to ad- 
mit of a rude bridge by which the opposite shores are connected. 
In this fresh water, cod are frequently taken ; and that the water is 
perfectly fresh is certain; as the tide is never sufficient to pass the 
strait of communication, merely damming the fresh water till the 
ebb again commences. The inhabitants seem to entertain no 
doubt that the cod remains there for a considerable time; but the 
subject not having particularly interested them, it remains to be 
discovered whether their residence is permanent or occasional, or 
whether they spawn there. If they reside there, even for any length 
of time, it is probable that this water contains other sea-fishes, by 
which they are tempted, unless they feed on trout; but I could not 
discoyer that any others had been found. 
