ficulties at the mines and in the railroads, and the
crowding of transportation facilities. The first cause is probably the
most important, and this is particularly true of anthracite coals where
a sliding scale of prices is used according to the season of the year.
While market conditions serve as one of the principal reasons for coal
storage, most power plants and manufacturing plants feel compelled to
protect their coal supply from the danger of strikes, car shortages and
the like, and it is customary for large power plants, railroads and coal
companies themselves, to store bituminous coal. Naval coaling stations
are also an example of what is done along these lines.

Anthracite is the nearest approach to the ideal coal for storing. It is
not subject to spontaneous ignition, and for this reason is unlimited in
the amount that may be stored in one pile. With bituminous coals,
however, the case is different. Most bituminous coals will ignite if
placed in large enough piles and all suffer more or less from
disintegration. Coal producers only store such coals as are least liable
to ignite, and which will stand rehandling for shipment.

The changes which take place in stored coal are of two kinds: 1st, the
oxidization of the inorganic matter such as pyrites; and 2nd, the direct
oxidization of the organic matter of the actual coal.

The first change will result in an increased volume of the coal, and
sometimes in an increased weight, and a marked disintegration. The
changes due to direct oxidization of the coal substances usually cannot
be detected by the eye, but as they involve the oxidization of the
carbon and available hydrogen and the absorption of the oxygen by
unsaturated hydrocarbons, they are the chief cause of the weathering
losses in heat value. Numerous experiments have led to the conclusion
that this is also the cause for spontaneous combustion.

Experiments to show loss in calorific heat values due to weathering
indicate that such loss may be as high as 10 per cent when the coal is
stored in the air, and 8.75 per cent when stored under water. It would
appear that the higher the volatile content of the coal, the greater
will be the loss in calorific value and the more subject to spontaneous
ignition.

Some experiments made by Messrs. S. W. Parr and W. F. Wheeler, published
in 1909 by the Experiment Station of the University of Illinois,
indicate that coals of the nature found in Illinois and neighboring
s