Igneous Origin of some Trap Rocks. 119 



Art. XIV. — Igneous Origin of some Trap Rocks. — Editor. 



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, eiitering 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 Volcanic Action. 



We have already adverted to the vast volcanic district of France,f 

 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 Etna ; and we have sketch- 



* See Vol. IV. for Prof. Cooper's lecture, and Vol. XIV. for the analysis and re- 

 view of the works of Scrope and Daiibeny. 

 1 See Vol. XIV. of this .Journal. 



