,000,000 tons. Within a few years, however, the decreased cost of
mining due to machinery, and the low rates of transportation to the
seaboard has developed an export trade to Russia, Germany, and France.

[Illustration: COAL]

A small amount of coal is imported into the United States. A superior
quality of Australian coal finds a ready market in Pacific coast points
as far north as San Francisco, and large quantities of Nanaimo, B.C.,
coal are sold in Oregon, Washington, and California. A small quantity of
the "slack" or waste of the Nova Scotia mines is imported to Boston to
be made into coke. The Canadian fields supply a considerable part of the
coal used in Montana.

=Coke and Coal-Tar Products.=--In the manufacture of iron and steel a fuel
having a high percentage of carbon free from volatile matter is
essential. The great cost of wood charcoal forbids its use, and so a
charcoal made from soft coal is used. Fat coal is heated in closed
chambers until the volatile matter is driven off. The product is "coke";
the closed chamber is an "oven." The ovens are built of stone or
fire-brick, in a long row. They are usually on an abrupt slope, so that
the coal can be dumped into the top, while the coke can be withdrawn
from the bottom, to be loaded into cars.

About three thousand one hundred and forty pounds of coal are required
to make a short ton of coke; from three thousand to five thousand cubic
feet of illuminating gas, together with varying amounts of coal-tar and
ammonia, are driven off and generally wasted. In a few instances
"scientific" ovens are in use for the purpose of saving these products;
but in the coal-mining regions such devices are the exception and not
the rule. The great waste of energy-products in the manufacture of coke
is partly offset by the employment of refuse and slack, which could not
be otherwise used.

There are more than five hundred and eighteen thousand coke-ovens in
the United States, of which eighty per cent. are in use. Most of them
are in the region about the upper Ohio River, and nearly half the total
number is in the vicinity of Connellsville. The region around
Birmingham, Ala., ranks next in number. The coke product of the United
States is more than twenty million short tons a year. This is
considerably less than the product of Great Britain, which is upward of
twenty-five million tons.

Most of the "scientific" ovens are near or in large cities where the
gas, after purificat