GRAYLING. 



171 



winter in high northern latitudes, streams 

 under the ice may retain a temperature not 

 much lower than some of the Alpine sources. 

 I have seen grayling in Carniola, in a source 

 not quite 50°; and as, in large bodies of 

 water, the deepest part, in frost, is generally 

 the warmest — about 40°, the temperature at 

 which water is heaviest, I see no reason why 

 grayling may not be habituated to such a 

 temperature — coolness being generally fa- 

 vourable to their existence. But see, the 

 fog which had filled the valley and hid the 

 mountains from our sight is clearing away, 

 and I fear it will be a hot day. Before the 

 sun becomes too bright is the best time for 

 fishing in such a day as this. As soon as 

 the fog is fairly off, the water flies will begin 

 to appear, and fish to sport. 



Phys. — I see the fog has already disap- 

 peared from the deep water in the meadow, 

 where I suppose the warmth of the air from 

 the considerable mass of the water is greater; 

 and which is further removed from the hills 

 sending down currents of cold air, from the 

 mixture of which with the moist warm air 

 above the river this phenomenon is produced. 



