20 PHYSIOGEAPHY. CLASS I. 



OBSERVATIONS. 



1. This gas is composed of phosphorus and h} r drogen, the 

 relative quantities of which have not yet been ascertain- 

 ed. Bubbles of this gas, passing through a liquid into 

 atmospheric air, undergo a spontaneous combustion, and 

 produce a smoke remarkable for its annular disposition. 

 If allowed to remain for some time in contact with water, 

 it imparts to it a disagreeable odour, and a bitter taste. 



2. The phosphorous Hydrogen-gas, is the product of 

 bogs and other humid places, which contain organic matter 

 in a state of putrefaction. It has been considered as the 

 cause of the ignis fatuus or jack o' lantern ; an opinion not 

 very probable, if we compare the properties of the gas with 

 the descriptions given of these luminous phenomena. 



GENUS II. ATMOSPHERIC-GAS. 

 1. PURE ATMOSPHEIIIC-GAS. 



Pure Atmospheric Air. JAM. Man. p. 2. Atmosphoe- 

 rische Luft. HAUSM. III. S. 762. 



Amorphous. Transparent. Expansible. 

 Sp. Gr. =: 1-0. It is nearly 800 times lighter than 

 pure Atmospheric-water. 



OBSERVATIONS. 



1. Pure Atmospheric-gas consists of 



Azote 78-999. 



Oxygen 21-000. 



Carbonic acid 0-001. BERZELIUS. 

 The proportion of azote and oxygen is constant, that of 

 carbonic acid is variable ; being sometimes higher, some- 

 times lower than that mentioned above. Air filled in 

 bottles at sea, at a considerable distance from the shore, has 

 been found to contain no carbonic acid at all. 



2. It constitutes the atmosphere, and surrounds the 

 whole globe. 



