LIMESTONE. 7 



the growing plant ; and it has the power of ac- 

 quiring and long retaining moisture ; thus ren- 

 dering a soil cool and nutritive to the plants that 

 vegetate in it. The power that lime has of ab- 

 sorbing moisture will be better understood, when 

 we say, that one hundred weight will, in five or 

 six days, when fresh, absorb five pounds of water, 

 and that it will retain in the shape of powder, when 

 slakened, or loosened, as is commonly said, nearly 

 one fourth of its weight *. 



That lime rehardens after being made soft, as 

 in mortar, is owing to the power which it has of 

 acquiring carbonic acid the fixed air of Dr. Black 

 from the atmosphere ; when the stone is burned, 

 it loses this principle, but re-absorbs it, though 

 slowly, yet in time, and it thus becomes as hard as 

 stone again : we unite it with sand to promote the 

 crystallization and hardening. The utility of lime 

 in various arts, agriculture, manufactories, and 

 medicine, is very extensive, and in many cases in- 

 dispensable ; and the abundance of it spread through 

 the world seems designed as a particular provision 

 of Providence for the various ejids of creation. 



* The weight of lime is very variable, differing in different 

 places ; but taking our lime at the average of eighty pounds to 

 the bushel, some idea may be conceived of the cooling nature of 

 this substance. . Lime, to be used as manure, must be in a pul- 

 verized state ; and by drawing on the land the quantity that we 

 do, we convey to every acre so dressed equivalent to two hundred 

 and fifty gallons of water, not to be evaporated, but retained in 

 the soil as a refrigerant to the fibres of vegetation. 



