18 PHYSIOGRAPHY, CLASS I. 



OBSERVATIONS. 



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 obtained free from all odour. It burns with a feeble 

 light in atmospheric air, and if mixed with it, produces a 

 detonating gas. It imparts neither odour nor taste to 

 water with which it has been kept in contact. 



2. The pure Hydrogen-gas is developed from several 

 kinds of rocks, limestone, beds of coal, &c. ; also from 

 pools and stagnant water in general ; and it is met with un- 

 der these circumstances in different countries all over the 

 globe. It is one of the most common sources of the per- 

 petual fires of the Pietra Mala, and other places in Italy, in 

 the north of Asia, &c. and occurs in several mines. 



2. EMPYREUMATIC HYDROGEN-GAS. 



Empyreumatic or carburetted Hydrogen Gas. JAM. Man. 

 p. 1. Kohlenwasserstoffgas. HAUSM. I. S. 64. 



Amorphous. Transparent. Expansible. 



Sp. Gr. = 0*5707. BERZ. Odour erapyreumatic. 



OBSERVATIONS. 



1. The empyreumatic Hydrogen-gas consists of 



Carbon 74-00. 



Hydrogen 26-00, according to BERZELIUS. 

 It burns with a very faint blue flame, and imparts neither 

 odour nor taste to water it has been in contact with. 



2. It is developed from marshes and stagnant pools, and 

 is also found in volcanic countries. It seems that the 

 above mentioned species, which is said by BERZELIUS to 

 burn with almost no flame at all, is different from the in- 

 flammable gas which occurs in coal mines, particularly 

 those of Newcastle and Liege, since the latter burns with 

 a bright flame. This gas is called fire-damp at Newcastle. 

 There are continual streams of it issuing from the coal 

 seams or the accompanying strata. It mixes readily with 



