CADY AND MCFARLAND.|] Composition of Natural Gas. 275 
largely determined by the presence of a sufficiently porous 
stratum in which it could be stored, and of a difficultly pene- 
trable cap over this stratum. 
All of these things make it very difficult to test this hypothe- 
sis quantitatively, and at present we wish only to state our be- 
lief in its possibility. j 
CONCLUSIONS. 
In this paper the results of the examination of forty-six 
samples of natural gas from several widely separated parts of 
the country are given. These lead to the following conclusions: 
First.—That helium is present in all cases except possibly 
one. It is inferred from this that it is present in all or nearly 
all of the gases issuing from the earth. 
Second.—The helium content of the gas tends to increase as 
the nitrogen increases, though no direct relation is observed. 
Third.—In Kansas, lines of isohelium and isoparaffin con- 
tent can be traced across the state, and these follow approxi- 
mately the lines of outcrop of the various geological strata. 
Fourth.—A very wide variation in composition is noted in 
the gases examined; hydrocarbons varying from 15 per cent. 
to 98 per cent., and helium from a trace up to 1.84 per cent. 
The Heating Power of Kansas Gas. 
A subject of great practical importance to the consumer of 
gas, as well as of theoretical interest to the chemist, is its heat- 
ing power or calorific efficiency. This, in the case of gaseous 
fuels, is expressed either in terms of British thermal units per 
cubic foot of gas, or of kilogram calories (large calories) per 
cubic meter. A British thermal unit (B. T. U.) is the amount 
of heat necessary to raise one pound of water one degree 
Fahrenheit. A kilogram calorie is the amount of heat required 
to raise one kilogram of water one degree Centigrade. 
There are two ways of obtaining some idea of the heating 
power of a fuel. 
One of these is to calculate the theoretical heat value on the 
basis of the chemical analysis. This is done by multiplying 
the percentage of each separate constituent of the fuel by the 
quantity of heat (in calories or B. T. U.) which may be ob- 
tained by burning a unit quantity of the pure substance under 
proper conditions. The several values thus obtained give, 
when added together, the heating value of the whole fuel. The 
