casioned by immense internal fires,—a theory which, upon the whole seems more reasonable, it is by no means necessary to suppose that those fires occupy any very large portion of the whole volume of the globe. There are about two hundred volcanoes on the whole surface of the earth. Now I find by calculation that if every one of these were supported by a volume of fire as large in circumference as Lake Erie, and ten times as deep, the whole space occupied by those subterranian fires, would not be more than the one thirty-five thousandth part of the whole volume of the globe. One of the largest earthquakes in modern times, was the one which destroyed Lisbon in 1755. That earthquake is said to have been felt at a distance of 2000 miles in every direction. But it would be easy to demonstrate from the laws of mechanical forces, that such an effect might have resulted from the action of a subterranean force, confined within the space of a few cubic miles. It is by no means necessary to infer the existence of an immense volume of fire adequate to the destruction of the globe, and held in reserve for that purpose.
But I reject this theory, not simply for the want of sufficient evidence in favor of it; but from what seem to me unanswerable objections against it.
The following reason for rejecting the theory of the fluidity of the central portions of the earth, may be found in Bakewell's Geology, page 433.
"If the earth" says Bakewell, "be composed of a solid crust or shell, surrounding a fluid mass, the internal fluid would be subject to the attraction of the Sun and Moon, or in other words would have its regular tides. We are not acquainted with any counteracting influence to prevent the action of this tide upon the solid shell."
The objection here stated appears to me to be fair and unanswerable. If the interior portions of our earth were in a fluid state, we would have earthquakes about every six hours, in comparison with which ordinary earthquakes
