NORTH-CAROLINA GEOLOGICAL SURVEY. 71 



Silica, 29.255 



Potash, 13.253 



Soda, ... 3.095 



Earthy phosphates, * 11.678 



Lime, 2.061 



Magnesia, 0.193 



Sulp. acid, 0.521 



Chlorine, 0.072 



60,128 



The organic matter, which is not taken into the account, is 

 equally valuable and important, both as furnishing materials 

 of growth and the preservation of an open condition of the 

 soils. 



43. Certain crops are raised expressly for the purpose 

 of improving the soil. These, when in blossom, are ploughed 

 in, and their subsequent decay furnishes the manure for the 

 succeeding crop. The kinds usually selected are those which 

 grow vigorously and send their roots deep. Such plants 

 bring from a great depth the fertilizing matter to the surface 

 where it becomes accessible to the succeeding crop. 



The red clover is the favorite plant in the Northern States. 

 Buckwheat is also employed, but it is objectionable : it con- 

 tinues to spring up from the seed as some will ripen and mix 

 with the wheat crop or appear as a weed in the corn and re- 

 quire eradication by the hoe. 



For the South the pea has become a favorite with intelligent 

 planters, and is, from its composition and adaptation to climate 

 the best crop to precede wheat and to act as its fertilizer. 



The composition of red clover is well adapted to the end 

 which it is designed to fulfil ; besides, its root is large, spreads 

 widely and sinks deeply, and hence it brings to the surface a 

 large amount of fertilizing matter. 



The ash of the green plant amounts to 1.06 per cent., when 

 dry to 5.87. 



On submitting the dry clover in the condition of hay to 

 analysis I found : 



' 



Potash, 25.930 



Soda, 14.915 



