3 1 4 Of the Propagation of Heat 



a vast quantity of Heat during the long summer days, 

 while they receive the influence of the sun's vivifying 

 beams ; this Heat, being given off to the cold air which 

 rushes in from the polar region, serves to warm it and 

 soften it, and consequently to diminish the impetuosity 

 of its motion, and take off the keenness of its blast. 

 But as the cold air still continues to flow in as the 

 sun retires, the accumulated Heat of summer is soon 

 exhausted, and all solid and fluid bodies are reduced to 

 the temperature of freezing water. In this stage the 

 cold in the atmosphere increases very fast, and would 

 probably increase still faster, were it not for the vast 

 quantity of Heat which is communicated to the air by 

 the watery vapours which are first condensed, and then 

 congealed, in the atmosphere, and which afterwards full 

 upon the earth in the form of snow; and by that still 

 larger quantity which is given off by the water in the 

 rivers and lakes, and in the ground upon its being 

 frozen. 



But in very cold countries the ground is frozen and 

 covered with snow, and all the lakes and rivers are frozen 

 over in the very beginning of winter. The cold then 

 first begins to be extreme, and there appears to be no 

 source of Heat left, which is sufficient to moderate it in 

 any sensible degree. 



Let us see what must have happened if things had 

 been left to what might be called their natural course, 

 if the condensation of water on being deprived of its 

 Heat had followed the law which we find obtains in other 

 fluids, and even in water itself in some cases, namely, 

 when it is mixed with certain bodies. 



Had not Providence interfered on this occasion in a 

 manner which may well be considered as miraculous, all 



