332 Of the Propagation of Heat 



water of the lake would give off an immense quantity 

 of Heat before a covering of ice could be formed on its 

 surface for its protection, it would, on the return of 

 spring, be found to be extremely cold ; and as it would 

 require a long time to regain from the influence of the 

 returning sun the enormous quantity of Heat lost dur- 

 ing the winter, it would remain very cold during the 

 spring, and probably during the greatest part of the 

 summer; and this could not fail to chill the atmosphere, 

 and check vegetation in the surrounding country to a 

 very considerable distance. And though a large lake of 

 salt water in a cold country would tend to render the win- 

 ter somewhat milder on one side of it, namely, on the 

 side opposite to the quarter from whence the cold winds 

 came ; yet this advantage would not only be confined to 

 a small tract of country, but would not anywhere be 

 very important, and would by no means counterbalance 

 the extensive and fatal consequences which would be 

 produced in summer by so large a collection of very 

 cold water. 



When the winter is once fairly set in, — when the earth 

 is well covered with snow, and the rivers and lakes with 

 ice, and more especially when the ice as well as the land 

 is covered with that warm winter garment, a few degrees 

 more of cold in the air cannot produce any lasting bad 

 consequences. It may oblige the inhabitants to use ad- 

 ditional precautions to guard themselves, their domestic 

 animals, and their provisions from the uncommon se- 

 verity of the weather; but it can have very little influ- 

 ence in the temperature of the ensuing summer ; and 

 even it is probable, if it influences it at all, that it tends 

 rather to make it warmer than colder. Lakes of salt 

 water could therefore be of no real use in winter in cold 



