232 Unwersity Geological Survey of Kansas. 
siderable heat by their combustion. Some of them are also light- 
producers, but these are present in such small quantities that a 
natural gas flame is usually nearly non-luminous. The hydro- 
carbons found in natural gas belong in two classes or series— 
the paraffins, or marsh-gas series, and the olefins, or the ethyl- 
ene series. Some of the members of these two series are fa- 
miliar as artificial products of the dry distillation of coal or 
wood, and are therefore usually found in coal- or producer-gas. 
METHANE.—In natural gas the chief member of the marsh- 
gas series is methane, or marsh-gas itself, having the formula 
CHa and a composition of 25.03 per cent. hydrogen and 74.97 
per cent. carbon by weight. The name marsh-gas comes from 
the fact that it is frequently produced by the decay of plants in 
swamps and the bottom of rivers. When pure it is a colorless, 
odorless gas, lighter than air and having a specific gravity of 
0.559. A liter of the gas weighs 0.7148 grams and a cubic foot 
weighs 312.36 grains. 
The boiling-point of liquefied methane, according to Ramsay 
and Travers, is —160.3° C."° Its critical temperature, that is, 
the temperature above which no amount of pressure will 
liquefy it, is —81.8° C. 
It will be readily seen, therefore, that ite even the highest 
~ pressures in the depths of the earth will suffice to hold it as a 
liquid if the temperature is above ordinary surface tempera- 
ture, as is usually supposed to be the case. 
When burned, one volume of methane unites with two vol- 
umes of oxygen, which is equivalent to ten. volumes of air. The 
products of the combustion are two volumes of water-vapor 
and one volume of carbon dioxid. This production of water- 
vapor becomes apparent in the combustion of natural gas, the 
water condensing and collecting on any cold object near the 
burning gas. This gives rise to the popular belief that the gas 
as it comes in the pipes is wet or loaded with water. A simple 
calculation will show us the remarkably large amount of water 
produced in the burning of a thousand cubic feet of methane. 
Each thousand cubic feet of methane produces on combus- 
tion twice its own volume, or 2000 cubic feet, of water-vapor. 
This weighs 100.18 pounds and is equal to approximately 
twelve U.S. gallons of liquid water. Now, if we have a natural 
gas containing 95 per cent. of pure methane, it would give 95 
113. Boiling-points and critical temperatures of liquefied gases used here are 
taken from Travers’ Experimental Study of Gases, London, 1901, p. 247. 
