52 



OUPTER V 



THE SOIL. 



CoirposiiuA \.i v nr m,ou; divided into an organic and an inorganic 

 part. Quantity, oiigin, necessity end constitution of organic 

 matter : how to 'n^ease it in the soil. Formation of mineral 

 part of soils; chiefly from limestones, sandstones and clays. 

 Classification of soils. Other substances present beside three 

 above named; their number and name.3. Cause of difference 

 between fertile and barren soils. 



SECTION I. THE PROPORTION AND ORIGIN OF THE ORGANIC 

 MATTER IN THE SOIL. 



Having: now become familiar with the substances 

 which are found in both the organic and the inorganic 

 parts of plants, we must next inquire what is the 

 connection between the plant and the soil. We find 

 that one soil produces better crops than another; that 

 plants will grow in some places, that will not flourish 

 at all in others; that manure is not needed on some 

 soils, while it is quite indispensable on others. The 

 reasons for these and many other differences that might 

 be mentioned, are only to be discovered by chemical 

 analyses of the soil itself. 



The first point which we are able to establish, is the 

 fact that here as in the plant, are to be found the two 

 great classes of organic and inorganic substances. If 

 a portion of soil is heated on a knife-blade or a thin 

 iron or tin plate, it will smoke and blacken; if the 

 heat be continued, the smoke will after a time cease, 

 the blackness disappear, and the remaining earth will 

 be usually of a whitish or reddish color* It is like the 



