ORGANIC CONSTITUENTS OF SOIL. 65 



from the soil, but also those which have been elaborated by 

 their living structure. The former are silicates and salts, or 

 the inorganic elements ; the latter are the organic parts of 

 soil. 



In the first edition of this work, chlorine was not enumer- 

 ated as an element of plants. Its presence in them was 

 considered accidental, because its source had not been de- 

 tected in the rocks, from whose ruins soil has been formed. 

 Dr. A. A. Hayes has detected alkaline chlorides in the pri- 

 mary rocks of Vermont. The possible existence of chloride 

 of silicon has been noticed. If this is not the source of the 

 chlorine of plants, that may be supposed to be evaporated 

 as a chloride from the ocean, and consequently to exist in 

 that state, dissolved in air. If derived from this salt in soil, 

 then that is extraneous. Its origin was suggested to be 

 oceanic. An examination of the rain-water, of each fall, 

 during the year 1842, in Lowell, has shown that this sugges- 

 tion is correct. Probably muriates are universally contained 

 in rain-water. As, therefore, common salt, the chlorine and 

 soda of plants is derived by evaporation from sea-water, 

 then as sulphate of lime has been detected in snow and hail, 

 it becomes a question, whether other inorganic salts of 

 plants may not have a similar origin, and exist dissolved 

 in air. 



Continued examination of rain water has shown that all 

 the mineral elements of plants are traceable in it. 



89. It is thus seen, that soil presents itself in a new view. 

 Soil consists of two grand divisions of elements. Inorganic 

 and organic. The inorganic are wholly mineral, they are 

 the products of the chemical action of the metallic, or unme- 

 tallic elements of rocks. They existed before plants or ani- 

 mals. Life has not called them into existence, nor created 

 them out of simple elements. Organic elements are the 



