Earths. 179 



and light, sometimes losing one-third, sometimes 

 one-half of its weight, and from a mild substance 

 Incomes active and acrid ; it is then called quick- 

 lime ; and if left upon a moist animal or vegeta- 

 ble substance it corrodes, and in some degree 

 dissolves it. If the lime is new burnt, however, 

 and the animal and vegetable substances are co- 

 vered with it, they will be parched up into a 

 hard or horny mass : this is occasioned by the 

 strong attraction which quick-lime ha* for moisture, 

 in consequence of which it extracts the water 

 they contain, as is evident, for if moisture is 

 added again to these substances, they become 

 soft and pulpy as before. This attraction for 

 water is one of the most remarkable qualities the 

 fire gives it ; for if water is poured upon burnt 

 lime, it crumbles by degrees into a fine powder, and 

 a great heat is produced, so considerable as to 

 set on fire a stick if put into it. It is therefore 

 very dangerous for ships to take in a cargo of 

 quick-lime. 



These facts are not difficult of explanation. Lime 

 is seldom found in a pure state, but almost con- 

 stantly combined with carbonic acid in the form 

 of chalk, limestone, marble, shells, &c., which 

 are all carbonates of lime. By heat the carbonic- 

 acid is driven off in the form of gas, and the lime 

 loses proportionably of its weight. It has then 

 a strong attraction for water, which, when poured 

 upon it, forms a real combination, the hydrat of 

 lime, in^a solid form. The condensation of the 



