LAWS OF HEAT. WATER. 85 



the beneficial course of things at the earth's sur- 

 face. Water contracts by cold; it thus equalizes 

 the temperature of various times and places ; but 

 if its contraction were continued all the way to 

 the freezing point, it would bind a great part of 

 the earth in fetters of ice. The contraction then 

 is here replaced by expansion, in a manner 

 which but slightly modifies the former effects, 

 while it completely obviates the bad conse- 

 quences. The further expansion which takes 

 place at the point of freezing, still further facili- 

 tates the rapid removal of the icy chains, in 

 which parts of the earth's surface are at certain 

 seasons bound. 



We do not know how far these laws of expan- 

 sion are connected with and depend on more 

 remote and general properties of this fluid, or of 

 all fluids. But we have no reason to believe 

 that, by whatever means they operate, they are 

 not laws selected from among other laws which 

 might exist, as in fact for other fluids other laws 

 do exist. And we have all the evidence, which 

 the most remarkable furtherance of important 

 purposes can give us, that they are selected, and 

 selected with a beneficial design. 



3. As water becomes ice by cold, it becomes 

 steam by heat. In common language, steam is 

 the name given to the vapour of hot water ; but in 

 fact a vapour or steam rises from water at all tem- 

 peratures, however low, and even from ice. The 



