the cost and difficulty of manufacture and
handling have made it impossible to place it in the market at a price to
successfully compete with coal.

Coke is a porous product consisting almost entirely of carbon remaining
after certain manufacturing processes have distilled off the hydrocarbon
gases of the fuel used. It is produced, first, from gas coal distilled
in gas retorts; second, from gas or ordinary bituminous coals burned in
special furnaces called coke ovens; and third, from petroleum by
carrying the distillation of the residuum to a red heat.

Coke is a smokeless fuel. It readily absorbs moisture from the
atmosphere and if not kept under cover its moisture content may be as
much as 20 per cent of its own weight.

Gas-house coke is generally softer and more porous than oven coke,
ignites more readily, and requires less draft for its combustion.

[Illustration: 16,000 Horse-power Installation of Babcock & Wilcox
Boilers and Superheaters at the Brunot's Island Plant of the Duquesne
Light Co., Pittsburgh, Pa.]

THE DETERMINATION OF HEATING VALUES OF FUELS

The heating value of a fuel may be determined either by a calculation
from a chemical analysis or by burning a sample in a calorimeter.

In the former method the calculation should be based on an ultimate
analysis, which reduces the fuel to its elementary constituents of
carbon, hydrogen, oxygen, nitrogen, sulphur, ash and moisture, to secure
a reasonable degree of accuracy. A proximate analysis, which determines
only the percentage of moisture, fixed carbon, volatile matter and ash,
without determining the ultimate composition of the volatile matter,
cannot be used for computing the heat of combustion with the same degree
of accuracy as an ultimate analysis, but estimates may be based on the
ultimate analysis that are fairly correct.

An ultimate analysis requires the services of a competent chemist, and
the methods to be employed in such a determination will be found in any
standard book on engineering chemistry. An ultimate analysis, while
resolving the fuel into its elementary constituents, does not reveal how
these may have been combined in the fuel. The manner of their
combination undoubtedly has a direct effect upon their calorific value,
as fuels having almost identical ultimate analyses show a difference in
heating value when tested in a calorimeter. Such a difference, however,
is slight, and very close approximations may be computed fr