LIMESTONE. 7 



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 ends of creation. 

 Lime, and siliceous substances, compose a very 

 large portion of the dense matter of our earth ; the 

 shells of marine animals contain it abundantly ; our 

 bones have eighty parts in one hundred of it ; the 

 egg-shells of birds above nine parts in ten during 

 incubation, it is received by the embryo of the bird, 

 indurating the cartilages, and forming the bones. 

 But the existence and origin of limestone are pre- 

 eminent amongst the wonders of creation ; nor 



* 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 pulverised 

 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. 



