ON WATER. 69 



completely analogous, and affording unerring 

 proof of one simple and uniform law. 



ON WATER. 



Water is next to be considered, and its im- 



fortance in every sense cannot be overrated, 

 t acts in a triple way : First, by its moisture 

 affording a supply of a necessary article in the 

 economy of plants. Secondly, by its solvent 

 properties, it is one of the means employed by 

 nature for rendering salts and other solid mat- 

 ters in a fit state to be absorbed and assimilated 

 by plants. And lastly, by its decomposition, 

 it furnishes hydrogen to combine with carbon, 

 nitrogen, and the various salts which enter 

 into the composition of vegetable products, and 

 restores its oxygen to the atmosphere, to sup- 

 ply the place of that consumed by man, and 

 all animals in the process of respiration. 



This is a mere outline of the important parts 

 it performs, and therefore it will merit some 

 farther consideration to comprehend its chemi- 

 cal analysis. In its ordinary state, water is 

 never pure; that is, it always contains carbonic 

 acid gas, the salts of lime, soda, magnesia, pot- 

 ash, and frequently ammonia; all of which are 

 essentially useful to promote vegetation — in- 

 deed, water in its pure state, will not of itself 

 support vegetable life, and its solvent power 

 is, therefore, one of its most important attri- 

 butes. 



In its chemical analysis, water yields oxy- 

 7* 



