C 20 J 



Chalks, calcareous marles, or powdered lime- 

 stones, act merely by forming an useful earthy ingre- 

 dient of the soil, and their efficacy is proportioned to 

 the deficiency of calcareous matter, which in larger 

 or smaller quantities seems to be an essential ingre- 

 dient of all fertile soils ; necessary perhaps to their 

 proper texture, and as an ingredient in the organs of 

 plants. 



Burnt lime, in its first effect, acts as a decompo- 

 sing agent upon animal or vegetable matter, and seems 

 to bring it into a state on which it becomes more 

 rapidly a vegetable nourishment ; gradually, however, 

 the lime is neutralized by carbonic acid, and conver- 

 ted into a substance analogous to chalk ; but in this 

 case it more perfectly mixes with the other ingredients 

 of the soil, is more generally diffused and finely di- 

 vided ; and it is probably more useful to land than 

 any calcareous substance in its natural state. 



The most considerable fact made known with 

 regard to limestone within the last few years, is owing 

 to Mr. Tennant. It had been long known that a par- 

 ticular species of limestone found in different parts of 

 the North of England, when applied in its burnt and 

 slacked state to land in considerable quantities, occa- 

 sioned sterility, or considerably injured the crops for 

 many years. Mr. Tennant in 1 800, by a chemical 

 examination of this species of limestone, ascertained, 

 that it differed from common limestones by containing 

 magnesian earth ; and by several experiments he 

 proved that this earth was prejudicial to vegetation, 

 when applied in large quantities in its caustic state. 



