Affinities of Earths. 1 i 



dity and duftility which proceed from its 

 power of retaining water, and of thefe pro- 

 perties magnefia alfo participates though in a 

 lefler degree. Siliceous Earths on the contrary 

 are charaaerifed by roughnefs, hardnefs, 

 lharpnefs to the touch, and a total want of 

 flexibility and adherence to each other, when 

 minutely divided, and a ready reparation from 

 water; of thefe properties calcareous and 

 ponderous Earths participate, though in a 

 leffer degree, 



CHAP II. 



Of the Affinities of Earths to each other. 



The above mentioned Earths are never 

 found in nature perfectly pure, but always 

 combined or mixed either with a faline or in- 

 flammable principle, or with each other, oj: with 

 fome metallic principle, particularly iron, be- 

 fides water; when mixed with any notable pro- 

 portion of the inflammable or metallic princi- 

 ples, or even of the faline, fo as to exhibit the 

 characters of fuch principles, they fhall be 

 treated of under thofe particular heads j I 

 fhall here confider only fuch compounds as 

 retain the general characters of Earths, and as 

 in conformity with Mr. Cronjted^ I intend 

 deducing the various fpecies. of Earths from 

 their union either with faline principles or 

 with each other, it will be neceflary to indi- 

 cate the affinities on which fuch unions are 



founded; 



