ion, is used for illuminating purposes. In some
instances the coke, and not the gas, is a by-product. The coal-tar is
used in part for fuel, but a portion of it goes to the chemical
laboratory, where it is made to yield ammonia, benzine, carbolic acid,
and aniline dyes to the value of nearly seven million dollars.

=Graphite.=--Graphite, plumbago, or "black lead," as it is popularly
named, is found in many parts of the United States, but only a few
localities produce a good commercial article; these are Ticonderoga, N.Y.,
which yields from six hundred to two thousand tons a year, and
Chester County, Pa., which yields a small but increasing amount; a good
quality is mined near Ottawa, Canada. It is extensively mined in Ceylon,
and this island produces the chief bulk of the world's ordinary product.
The finest grade comes from the Alibert mine in Siberia. A good article
is manufactured artificially at Niagara Falls.

Graphite is used as a stove polish and for crucibles; in the main,
however, it is employed in the manufacture of lead[41] pencils; for this
purpose only a very soft mineral, absolutely free from grit, is
employed, and the Siberian output is used almost wholly. One German firm
and two American firms supply most of the pencils used.

=Petroleum.=--Petroleum is the name given to a natural liquid mineral from
which the well-known illuminating oil "kerosene" is derived, and to
obtain which it is mined. Petroleum is a mixture of various compounds
known as hydrocarbons. Some of these compounds are gaseous, some are
liquid, and some are solid; all of them are articles of commercial
value. The petroleum from different localities differs greatly in
appearance and composition.

The pitch that coated Noah's ark, the slime of the builders of the Tower
of Babel, and the slime-pits of the Vale of Siddim all refer to mineral
products associated with petroleum. Under the name of "naphtha" it has
been known in Persia for thirty centuries, and for more than half as
long a flowing oil spring has existed in the Ionian Islands. The Seneca
Indians knew of a petroleum spring near the village of Cuba, N.Y., and
used it as a medicine long before the advent of the white man.

As early as 1850 illuminating oil, known as "coal" oil, was made in the
United States by distilling cannel coal, but this product was supplanted
within a few years by the natural petroleum discovered in Pennsylvania.
In 1859 Colonel Drake completed a well bore