Art. VIII. — Water and its Impurities, with Reference to 

 the Supply of Large Towns. By Jacob S. Mosher ; M.D. 



[Read before the Institute, March 20, I860.] 



A large portion of the earth is covered with water, ex- 

 posing its surface to the action of the sun and air. Influ- 

 enced by these great masses to rise in the form of vapor, 

 which from changes in temperature and other causes are 

 again condensed and return to their original position. 

 From whatever part of the earth this vapor rises it is 

 always the same ; unaffected by the condition of the water 

 from which it is produced, salt or fresh, it is uniformly of 

 one constitution by the time it is returned from the clouds 

 to the surface. 



When thus precipitated as rain it is the nearest approach 

 to pure water that is ever found in nature. It contains 

 a large amount of atmospheric air, besides several well 

 known chemical solids and gases, which are generated in 

 the atmosphere from electrical and other causes. These 

 last are in such small proportions that they may be disre- 

 garded ; the dissolved air which is rich in oxygen, instead 

 of being deleterious, adds to the value of water in the 

 manifold uses for which that fluid seems designed, making 

 in fact the difference between fresh spring water and the 

 same after it has been boiled. We may therefore consider 

 rain water before it has reached the earth in its fall, as 

 pure for practical purposes. 



The amount of rain that falls in the frigid zones is 



1.25 feet per annum. 



In Asiatic Russia, 13.5 inches. 



" United States, 39 



"Albany, (Average for 24 years), 40.93 " 



" Tropical regions of Eastern continent, 79.7 " 



" " " Western continent, * 113 " 



