155

thracite essentially only in being unable to support combustion
under ordinary conditions.

Intersecting the shales in which the coal is found are several
dykes and sills of the Etheline volcanics, like those shown in
Figures 8 and 9 on pages 71 and 72. The metamorphosing action
of these igneous rocks, through the application of heat, is believed
to have deprived the coal of its volatile constituents, and, to have
left it in its present condition.

That molten igneous rocks intersecting coal seams exert
a strong devolatilizing action on the coal is well known,! and
also that this action is effective only locally.2_ This localization
of the metamorphosing effect will explain why only a part of the
Cretaceous coals on Graham island are anthracitic.

In the anthracitic district of Graham island, the intrusive
bodies have been shown to be particularly abundant and some
are of considerable size (the 50-foot dyke near Anchor cove for
instance); and the intrusives in general have been accompanied
by considerable volumes of heated waters. It is thought that
these heated waters, in part perhaps in the gaseous state, have
permeated the strata and devolatilized the coal seams to the
extreme extent now seen.

The hot waters or gases are believed to have been even more
potent in their action, through their transference of heat by
convection, than through the baking of the coal by conduction.
The latter process is very slow,’ while any contact metamorphic

deposit gives evidence of the efficiency of heat transfer by

heated waters.*

In place of the above theory, that contact metamorphism
was the effective agent, the regional metamorphism hypothesis
deserves consideration. This hypothesis in brief considers the
degree of anthracitization to be proportional to the degree of
deformation of the enclosing strata. This hypothesis seems in-

1 Willis, Bailey., Tenth Census U.S.A., vol. 15, 1883, p. 763.
Lee, W. T., Cited by D. White, U. S. Bureau of Mines, Bull. 38, p. 103.
Newberry, J. S., Sch. of Mines Quart., vol. 8, 1886-87, p. 334.
Taff, J. A., Science, N.S., vol. 23, 1900, p. 696.
Storrs, L. S., 22nd Ann. Rept., U.S. Geol. Surv., vol. 3, p. 430.
2 White, D., U. S. Bureau of Mines, No. 38, p. 104.
3 Ingersoll, L. R., Econ. Geol. vol. 8, 1913, p. 230.
4 Lindgren, W., Econ. Geol. vol. 9, 1914, p. 290.