THE TEMPERATURE 77 



but by that time another change, a 

 change affecting the habits of the trout, 

 has come over the conditions of the lake. 

 Even as the shallows were the first places 

 to be warmed when the sun waxed early in 

 the year, they are the first to become cold 

 when the frosts, as they are wont to do, 

 return. It is always on the shallows that 

 the first ice appears. Thus, a " cold snap " 

 in early spring will cause the temperature 

 of the shallows to fall below the mean 

 temperature of the lake. A similar result 

 comes of another cause, which seems to 

 have escaped general notice. During a 

 succession of sunshines early in the year, 

 the shallows near the shore have day by 

 day been made warmer than the deeps ; 

 but all the time that this has been going 

 on it is the deeps that have been most 

 surely gaining. Nightly the shallows 

 have lost most, if not all, the warmth of 

 the day ; but by night as well as by day 

 the deeps have been storing nearly all that 

 they received. They have been retaining 

 all except the comparatively small portion 



