GEOLOGICAL SOCIETY. 



123 



FOURTH CLASS — COMBUSTIBLES. 



H. from 0 to 4. 



G. from 0, 7 to % 2. 



When G. from 1, 9 to 2, 2 : H. 2| and less, 

 and streaky from metallic black to 

 gray, or common lustre and yellow 

 color, or easily electric by friction* 



FIRST CLASS, FIRST ORDER— HYDROITE. 



H. from \ to 2. 



G. from 0, 92 to 0, 95 i Cooling soluble on the tongue. 

 Examples, ice, hail, snow, hoar frost. Ice 

 in rhombohedrons, according to Sir David 

 Brewster. 



SECOND ORDER— CARBONATE, 



Mono- axis. 



H. from 1 to 2|. 



G. from 1, 4 to 2, 1. 



Alkaline taste ; examples — natron, trona. 



THIRD ORDER— HALATE. 



H. from \\ to3J. 

 G. from 1, 5 to 2, 2. 



Urinous and sweet taste 5 examples — sal ammoniac, rock 

 salt. 



