SF. Peckham—The Origin of Bitumens. 115 
Chicago is indigenous, the invasion of that limestone by steam 
under high pressure would cause the petroleum to accumulate 
in any rock lying above, porous or fissured sufficiently to 
receive it. ‘The mingling of oils that produce asphaltum and 
those that contain paraffine, and the occurrence of paraffine in 
large masses in porous strata filled with the remains of fucoids 
and marine animals that flank the core of crystalline schists 
in Roumania and Galicia, offers the strongest support to this 
hypothesis. The fact that the eruptive rocks of Lake Superior 
and the metamorphic rocks farther east prevail to such an 
extent that that vast inland sea has been supposed to be the 
crater of an extinct volcanic lake lends the strongest support to 
an hypothesis that regards the vast accumulations of petroleum 
in Western Canada as due to invasion of strata on the borders 
of this heat-center, in which the petroleum is indigenous, by a 
sufficiently elevated temperature to cause its distillation. 
Mud volcanoes and hot springs, it appears to me, are prop- 
erly regarded as the phenomena attending the gradual subsid- 
ence.of metamorphic action in the crust ofa cooling earth. e 
accompanying petroleum or maltha is but the accident of such 
phenomena when strata containing organic remains are still 
invaded at a great depth by a temperature sufficiently elevated 
to effect the distillation of their organic contents. Gas springs 
may own the same origin, or the gas may escape from deep-seated 
reservoirs, the product of a distillation long since completed. 
lid bitumens of the fourth class occur in great variety. 
The universal distribution of bituminous material in rocks 
was noticed in 1823 by the Hon. Geo. Knox. e occurrence 
of disseminated bitumen in metamorphic rocks, supposed to be 
Laurentian, at Nullaberg, in West Sweden, has been described ; 
also in the lower Silurian of south Scotland; in trap near New 
aven, Connecticut; and in northern New Jersey, all of 
which are manifestly the results of the action of heat upon the 
organic matter in stratified rocks. The occurrence of bitumin- 
ous limestones in France and in the valley of the Rhone has. 
been attributed almost unanimously by French geologists to 
the action of igneous or metamorphic agencies. 
There remain the phenomena attending the occurrence of 
large veins of solid bitumen in Cuba, West Virginia, New 
Brunswick and elsewhere, for which no adequate explanation — 
as been proposed that does not regard them as the product 
of distillation from deep-seated strata, which has been projected 
into a fissure formed by the sudden rupture of the earth’s crust. 
r. R. C. Taylor examined the vein which occurs in metamor- 
phic rocks near Havana, and concluded that, “it was evidently 
ori eer an irregular open fissure, terminating upward in a_ 
wedge-like form, having various branches, all of which have 
