224 ELEMENTS OF SOILS. 



loses, in drying, one-fourth at least ; fruits and tubers, from 85 to 93 per cent ; grains, 

 from 50 to 90 per cent. Water therefore performs an essential function in organized 

 matter. 



Water is colorless, transparent, destitute of taste and smell. It is solid at 32° Fahr. if 

 agitated ; if quiet, it may be reduced f^till lower, and retain its fluidity; but if then agi- 

 tated, it solidifies, and its temperature rises to 32°. In these changes, its bulk or vohmie 

 is also altered. During the act of solidifying, it expands with great force : even its expan- 

 sion begins at 40°. Water passes into steam or vapor at 212° F. ; one cubic inch of water 

 expanding to one foot of steam, or 1728 cubic inches. The boiling point, however, is de- 

 termined l)y the pressiue of the atmosphere, which, at the level of the sea, is equal to a 

 column of mercury 30 inches high. 



Water is never pure. It dissolves the air, a great number of gases, and various saline 

 matters, as salt, sulphates, nitrates and carbonates. Where these ingredients are in excess, 

 the waters are called mineral waters, and exert very frequently an important efiect upon 

 the animal system. 



The foreign bodies most frequently present in water, are carbonic acid, ammonia, and 

 atmospheric air ; and when it has fallen upon the earth, and has issued again in springs, 

 or collected in wells, the number of its foreign ingredients is increased. 



Of the amount of gases which water is capable of dissolving, we may state, that ac- 

 cording to the latest practical chemists, they stand as follows : 



Sulph'ireticd hydrogen, 253.0 volumes. 



Chlorine, 434.0 " 



Carbonic acid, 205.0 " 



Oxygen, 12.5 " 



Nitrogen and hydrogen, 0.6 " 



Although water scarcely dissolves nitrogen, yet it dissolves atmospheric air; and it is 

 this which gives it a pleasant and lively flavor, so refreshing when compared to distilled 

 or boiled water from which the air is expelled. 



Sea water contains the accumulated soluble matters of all climes, which have been 

 transported to this great reservoir by rivers. When this water is frozen, the salts are 

 excluded from the ice ; and hence, in high latitudes, fresh water is obtained by melting 

 blocks of ice. 



Water is the standard with which the weights of all other solids and liquids are com- 

 pared : it is 1 in the scale of specific gravities. In this comparison, equal bulks or volimies 

 are compared ; thus, a cubic inch of granite is found to weigh 2^ times as much as an 

 equal volume of water. 



The atmosphere. The constituents of the atmosphere have been given. It is a body 

 of aeriform matter surrounding the earth, and exerting a pressure equal to 15 lbs. on 

 the s(iuare inch. Tlie atmosphere is supposed to be acted upon by two forces, which 

 conjointly fix its limits, namely, its own elasticity, and the earth's attraction. Refraction 



