PHYSIOGRAPHY. CLASS i. 



ture investigations of their angles. The grains of hail 

 are compound, like other products of a similar formation. 

 Those which fall during the changeable season of spring 

 have the form of spheric sections, consisting of thin 

 prisms, radiating from the centre, which prisms are co- 

 lumnar particles of composition, and commonly opake. 

 The hail formed during heavy thunder-storms, in general 

 affects the shape of irregular, flattish globules; it is 

 likewise compound, but often perfectly transparent, and 

 including air bubbles. 



2. The pure Atmospheric-water occurs in the shape of 

 dew, mist, rain, snow, hail, ice, &c. ; also in springs, rivers, 

 lakes, &c. In many instances it is found with admixtures 

 of saline solutions, particularly in the sea. In the one or 

 the other form, it is spread all over the globe. 



ORDER III. ACID. 

 GENUS I. CARBONIC-ACID. 

 1. GASEOUS CARBONIC-ACID. 



Aeriform Carbonic Acid. JAM. Man. p. 4. Kohlensiiure. 

 HAUSM. III. S. 792. 



Amorphous. Transparent. Expansible. 

 Sp. Gr. = 1-51961. BIOT and ARAGO. Taste 

 slightly acidulous, pungent. 



OBSERVATIONS. 



1. The gaseous Carbonic-acid consists of 

 Carbon 27'40. 

 Oxygen 72'60. BERZELIUS. 



It suffocates animals, and extinguishes fire. It reddens the 

 blue tincture of litmus ; but the original colour very soon 

 returns. It produces a copious precipitate in a solution of 

 quicklime in water; and is itself absorbed by water, to 

 which it communicates its acidulous taste. 



