metamorphism of mountain chains--which have hastened the distillation,
and out of known earlier groups have produced the last. For example,
trap outbursts have converted Tertiary lignites in Alaska into good
bituminous coals; on Queen Charlotte's Island, on Anthracite Creek, in
southwestern Colorado, and at the Placer Mountains, near Santa Fe,
New Mexico, Cretaceous lignites into anthracite; those from Queen
Charlotte's Island and southwestern Colorado are as bright, hard, and
valuable as any from Pennsylvania. At a little distance from the focus
of volcanic action, the Cretaceous coals of southwestern Colorado have
been made bituminous and coking, while at the Placer Mountains the same
stratum may be seen in its anthracitic and lignitic stages.

A still better series, illustrating the derivation of one form of carbon
solids from another, is furnished by the coals of Ohio, Pennsylvania,
and Rhode Island. These are of the same age; in Ohio, presenting the
normal composition and physical characters of bituminous coals, that
is, of plant tissue generally and uniformly descending the scale in
the lapse of time from the Carboniferous age to the present. In the
mountains of Pennsylvania the same coal beds, somewhat affected by the
metamorphism which all the rocks of the Alleghanies have shared, have
reached the stage of _semi-bituminous_ coals, where half the volatile
constituents have been driven off; again, in the anthracite basins of
eastern Pennsylvania, the distillation further effected has formed from
these coals _anthracite_, containing only from three to ten per cent. of
volatile matter; while in the focus of metamorphic action, at Newport,
Rhode Island, the Carboniferous coals have been changed to _graphitic
anthracite_, that is, are half anthracite and half graphite. Here,
traveling from west to east, a progressive change is noted, similar to
that which may be observed in making a vertical section of a peat bog,
or in comparing the coals of Tertiary, Mesozoic, and Carboniferous age,