PHYSIOGRAPHY. 273 



Hydrogen Hypersthene. 

 HYDRO-CARBONATE OF LIME AND MAGNESIA. 



A variety of Calcareous Spar or Dolomite, found in veins and 

 irregular masses, in an amygdaloid of a loose texture, accompani- 

 ed by zeolitic minerals and the common Calcareous Spar, at Derry 

 in the north of Ireland. * 



HYDROGEN. Pure Hydrogen-Gas. MOHS. 



Amorphous. Transparent. Expansible. 



Sp. gr. = 0-0688. BERZ. 0-0732. BIOT and ARAGO. 

 Odor peculiar. 



1. Hydrogen-Gas, as it is found in. nature, is generally in a state of 

 combination. By the assistance of chemical processes, it may be ob- 

 ained, free from all odor. It burns with a feeble light in atmospheric 

 air, and if mixed with it, detonates when inflamed. It imparts neither 

 aste nor odor to water, with which it is kept in contact. 



2. Hydrogen-Gas is developed from several kinds of rocks, limestone, 

 beds of coal, &c. ; also from pools and stagnant water in general ; and 

 t is met with under these circumstances in different countries through- 

 out the globe. 



HYDROLITE. (See Gmelinite.) 



HYDROPHANE. (See Opal.) 



HYDROPHYLLITE. (See Appendix.) 



HYDROSILICITE. (See Kerolite.) 

 HYPERSTHENE. Prismatoidal Schiller- 

 Spar. MOHS. 



Primary form. Obliqne rhombic prism. M on M = 

 about 93. 



Secondary form. Primary, having the acute lateral 

 edges bevelled. Warwick, (N.Y.) 



Cleavage, parallel to the sides and base of the primary 

 .prism, more perfectly, parallel to the shorter diagonal of 

 that form, traces parallel to the longer diagonal of the same. 

 Fracture uneven. 



