FREEZING AND THAWING. 67 



the buds set, and all vegetable nature prepared for the 

 winter. This, like all the operations of nature, is 

 simple, and therefore it is unheeded by those who walk 

 the world in quest of wonders, but it is not, on that 

 account, the less beautiful or the less worthy of a place 

 in the description of that wonderful creation, among 

 the parts of which the connexions are so many and so 

 intimate, that is not easy to say which is most to be 

 admired in itself, or most conducive to practical wis- 

 dom. As soon as the thinnest pellicle of the water is 

 touched by the cold air, it sinks to the bottom, very 

 slowly, and probably regaining a little heat as it de- 

 scends ; and this process goes on till the whole mass, 

 however deep, be cooled down to 39^. This process 

 is exceedingly slow, because of the thin pellicle of the 

 water that sinks ; and it is interrupted during the days 

 (the weather at the time of the first frosts being serene 

 in the high latitudes) as when the sun-beams fall on 

 the surface they diminish the density, and thereby pre- 

 vent the process of descending, until the sun be set, 

 and the atmosphere again cool. Even the small angle 

 at which those beams fall upon the surface of the water, 

 tranquil as it is at that time, becomes a source of heat ; 

 they do not penetrate the water, but are reflected into 

 the air which, thus heated, is dispersed over the sur- 

 rounding land. 



Where the lake or other portion of water is very deep, 

 this process of cooling the whole down to 39| is not 

 completed till the year has revolved, and the warmth 

 again returns with the sun ; and even when the depth 

 is not sufficient for that purpose, there* is another ad- 

 vantage in the expansion of the water when it cook 



