SIMPLE HYDROCARBONS. 321 
Il. OXyYGHNATED HyprocarBons: mostly resins. 
III. ASPHALTUM AND MINERAL COALS. 
I, SIMPLE HYDROCARBONS. 
Marsh-Gas.—Light Carburetted Hydrogen. 
Colorless and inodorous gas in the pure state. Inflam- 
mable, and burns with a yellow flame. Composition Cl= 
Carbon 75, hydrogen 25=100. 
Obs. This gas (mixed with more or less carbon dioxide 
and nitrogen) often rises in bubbles through the waters of 
marshes, whence its name; and frequently it is discharged 
from fissures into coal mines in large quantities, constituting 
the fire-damp of the mine. Such natural discharges, called 
blowers, sometimes continue for months. It is the cause of 
the explosions in mines, a mixture of it with the atmo- 
sphere exploding on the approach of the flame of a can- 
dle. It destroys life both by the concussion occasioned, by 
the exhaustion of the atmosphere of oxygen, and by the 
production of carbon dioxide which takes place. ‘The gas 
which issues from the oil springs or wells of Western New 
York (Fredonia), and Eastern Pennsylvania, is marsh-gas 
mixed with other vapors of the Marsh-gas series. It is used 
in some places for lighting houses, and even villages ; and 
also for other purposes where heat is required. 
The gas bubbling up from a marsh in Europe afforded 
Websky Carbon dioxide 297, marsh-gas 43:36, nitrogen 
53°67=100. The first of these ingredients is in fact one 
of the more abundant results of decomposition, whether 
vegetable or animal; and the percentage is here small 
because the gas is soluble in water, and because it readily 
enters into combinations with the earthy inercdients of 
plants. 
Petroleum. 
Mineral oils, varying in density from 0:60 to 0:85. Solu- 
ble in benzine orcamphene. ‘They consist chiefly of liquids 
of the Naphtha and Ethylene series. The composition of 
the Naphtha or Marsh-gas series is expressed by the general 
formula, C,H,,+2, of which Marsh-gas is the first or 
lowest term; and that of the Ethylene series by the for- 
mula, O,H:,=Carbon 85°71, hydrogen 14:29=100. The 
oils vary greatly in density from the lightest naphtha, too 
