28 CHYMISTRY APPLIED TO AGRICULTURE, 



, Carbonate of lime .... 10 

 Carbonate of magnesia ... 3 



Oxide of iron 2 



The second 



Silex in grains 22 



Silica 15 



Alumina 45 



Carbonate of lime . . . . 11 

 Carbonate of magnesia ... 4 



Oxide of iron 3 



The third 



Silex in grains 19 



Silica 24 



Alumina 40 



Carbonate of lime .... 9 

 Carbonate of magnesia ... 5 



Oxide of iron 3 



The other principles were the remains of manures part y 

 decomposed. These three portions of soil were from land 

 which produced but little. The water which stands upon 

 clayey soils is always turbid and whitish, especially when 

 agitated by the winds ; heat has the effect of chapping 

 and splitting these soils, and hardens them so, as to ren- 

 der them nearly impenetrable to the plough ; in order to 

 give them fertility it is necessary to employ a great deal of 

 undecomposed barn-yard manure and litter ; and it is 

 advisable to sow, in the spring, crops of buck-wheat. 



The soils which are formed of the waste, or from the 

 decomposition, of mountains of calcareous free-stone, or 

 af the carbonate of lime, whether primitive or secondary, 

 frequently present only a mixture of calcareous sand, of 

 which the grains are united by a carbonate of the same 

 nature. These earths are in general light, porous, and 

 well suited to many kinds of cultivation, especially in 

 rainy climates, provided the bed be of sufficient depth, 

 and formed upon a basis of rock, to enable it to retain 

 the quantity of water required by the wants of vegetation ; 

 they are well adapted to the cultivation of the vine, and of 

 sainfoin ; and when they can be well manured will produce 

 good crops of rye, oats, and barley. These soils have re- 

 ceived the name of calcareous, though they almost always 

 contain other principles, because the properties of the 

 carbonate of lime predominate so much over those of the 

 other substances, that the latter are hardly perceived* 



