16 Cox. 
in the ash, but this saving would hardly be a compensation for 
the cost of mixing. 
From the above it is evident that purchasers of coal under 
contracts based on the heating value should first give due care 
to many other conditions which effect the choice of a grade of 
coal, such as: The kind of equipment, namely, whether the fur- 
naces and other equipment of the boiler setting in which the 
coal is to be consumed are adapted to the kind of coal under 
consideration; the friability and fineness of division of the coal; 
the labor conditions, by which is meant the amount of weight 
that it is necessary to handle in order to get a unit of heat; 
and last, but not least, the amount of ash and its fusibility, for 
these factors have.a large influence on the behavior of the coal 
in the furnaces. Having once decided on the kind of coal that 
it is desired to purchase, I believe that the delivery of and 
payment for the coal could be made advantageously entirely on 
an efficiency basis. 
Granting the usefulness of Philippine coal for steaming pur- 
poses, there are other points to consider, namely, the economy 
and the preservation of the supply. In developing, opening up, 
and working the mines, there is always a large amount of out- 
crop coal and slack that is unsuited for steaming purposes and 
which for sake of economy should be used. Experiments with 
a producer-gas plant® have shown that it is possible to use 
lignites and other poor coals in a gas producer to develop gas 
for a gas engine, and that the gas from the poor coals has as 
high a calorific value as that from any other coal which was 
used. Even when coals burn satisfactorily under a boiler, the 
process is wasteful as compared with their consumption in a 
producer-gas plant for the generation of gas-engine power. 
Mr. M. R. Campbell,° a member of the committee in charge of the 
producer experiments and of the coal-testing plant, says: “In every case 
the power produced by one pound of coal in the producer is many times 
the power produced by the same amount of coal in the steam plant. The 
ratios of these results run from 1.96 to 3.34; that is, the very best West 
Virginia coal yielded practically three and one-third times the amount of 
power when used in the producer that it did in the steam plant, the 
very poorest coal yielding in the producer practically double the amount of 
power that it did in the steam plant.” 
Dr. A. J. Holmes, another member of the committee, says: “We were 
careful in any of this work, where we would get the boiler test, to find 
out how many pounds of coal were necessary to develop a horsepower per 
hour, and found that when we put that same coal through the gas producer 
° Prof. Papers U. S. Geol. Surv. (1906), No. 48, pt. 3. 
* Econom. Geol. (1907), 2, 287. 
