Igneous Origin of some Trap Rocks. 119 
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Arr. XIV.—Igneous Origin of some Trap Rocks —Eniror. 
INTRODUCTORY REMARKS.—VOLCANOS. 
In former volumes of this Journal we have repeatedly called the 
attention of its readers to the evidence of the existence of fire in the 
interior of our planet.* Hecla, Etna, Vesuvius, Sumboa, Cotopaxi, 
Teneriffe, Kirauea, and nearly two hundred more active volcanos 
still continue to shake the earth by their convulsions, and to devastate 
the countries at their feet by their eruptions. Even long intermis- 
sion in their activity affords no ground of confidence that the repose 
of the earth will not be again disturbed. Vesuvius has, in various 
instances, been quiet for centuries, till forests have come to crown its’ 
crater, and vineyards and villas to adorn its declivities. The first 
seventy years of the christian era saw Herculaneum, Pompeii and 
Stabia, flourishing in this condition, at its feet: a dense population, 
active in business or war, or sunk in voluptuousness, dreamed not of 
impending ruin: although their streets were paved with the lava 
of ancient eruptions, the inhabitants heeded not the legend which 
perhaps told them of the dormant fire of the olden time, and of 
rivers of molten rock, and of ignited stones flying through the air, 
and of showers of cinders and ashes veiling the sun and oppressing 
the earth. But the ruin came, and those who have been born almost 
eighteen centuries later, are now walking the streets, entering the 
houses, and collecting the relics of these disinterred towns. 
It is equally impossible then to doubt either the present existence 
of great subterranean fires, or that in former periods of the planet, 
they were much more extensive and terrific in their operations, than 
at the present day. 
Ancient Volcame Action. 
We have already adverted to the vast volcanic district of France, 
where (although history and tradition are silent on the subject) for 
fifty leagues in both diameters, the evidences of volcanic action are 
as palpable as at the foot of Vesuvius or Eta; and we have sketch- 
* See Vol. IV. for Prof. Cooper’s = and Vol. XIV. for the. analysis and re- 
view of the works of Scrope and Dauben 
* See Vol. XIV. of this Journal. 
