C art J 



9 Charcoal. 

 15 Oxide of iron. 

 3 Saline matter. 

 Sulphate of potash. 

 Muriate of magnesia, with a minute 



quantity of vegetable alkali. 

 The remainder alumina and silica. 



Mr. Boys estimates that 266O bushels are the 

 common produce of an acre of ground, which, accor- 

 ding to his calculation would give 172900 Ibs. con- 

 taining 



Carbonate of lime 69 1 60 Ibs. 

 Gypsum - 9509.5 



Oxide of iron 12967.5 



Saline matter 2593.5 



Charcoal 7780.5 



In this instance there was undoubtedly a very 

 considerable quantity of matter capable of being ac- 

 tive as manure produced in the operation of burning. 

 The charcoal was very finely divided ; and exposed 

 on a large surface on the field, must have been gradu- 

 ally converted into carbonic acid. And gypsum and 

 oxide of iron, as I mentioned in the last Lecture, seem 

 to produce the very best effects when applied to lands 

 containing an excess of carbonate of lime. 



The second specimen was from a soil near Cole- 

 orton, in Leicestershire, containing only four per cent, 

 of carbonate of lime, and consisting of three-fourths 

 light siliceous sand, and about one-fourth clay. This 

 had been turf before burning, and 100 parts of the 

 ashes gave 



