mage to springs and fountains; but the water in wells becomes foul for a short time.
XI. That they are more frequent in the neighbouring countries of a vulcano.
This last circumstance, in my opinion, has led all inquirers in this question, out of the true path; therefore I propose in the ensuing paper.
I. To shew what it is not; the insufficiency of the vulgar opinion, of subterraneous fires and vapours.
II. To show what it is in reality, as it appears to me.
III. I shall conclude with the moral use we ought to make of these prodigies of nature.
I. The struggles of subterraneous winds and fires, that should heave up the ground like animal convulsions, seem to me impossible: Their powers, and manner of acting (if such there be) is quite incapable of producing the appearance of an earthquake. That these should operate instantaneously, in one minute, thro' a circle of 30 or 40 miles diameter, or more, I could not conceive. Nor that there should be any possible, much less ready passage thro' the solid earth, for such nimble agents, as every one is apt to imagine, that speak of this appearance; without sufficiently reflecting on the insuperable difficulties in that hypothesis.
We cannot pretend to deny, that there may be such vapours, and fermentations, inflamma-