_Mrs. B._ On this, as well as on most other philosophical subjects, the opinions of the learned vary. Mr. *****, who was a great naturalist, imagines some to be produced by fire, in the manner of volcanoes; others, by the struggles of confined air, expanded by heat, and endeavouring to get free. But there does not appear any sufficient reason for this distinction. The union of fire and air seems necessary to effect the explosion; since the former is an agent of no power, without the aid of the latter. _Ferdinand_. But pray, mamma, how does heat get into the inside of the earth? _Mrs. B._ There are hidden in the bowels of the earth, immense quantities of inflammable matter: pyrites, bitumens, and other substances of a similar nature, which only require moisture to put their fires in motion. Water readily finds its way into the greatest depths of earth: or even from subterraneous springs, this dreadful mixture may occur, when immediately new appearances ensue; those substances which have lain dormant for ages, and which, had they not met with this new element, would have remained so for ages longer, appear suddenly to have changed their nature: they grow hot, produce new air, and require room for expansion. The struggles this air then makes to get free, throw all above into convulsions, and produce those dreadful catastrophes which we so properly denominate earthquakes. This appears the most rational means of accounting for this phenomenon; I have not, therefore, thought it needful to enter into the theoretical speculations of philosophers upon the subject. _Ferdinand._ Well, mamma, directly I read, in Henry and Lucy, an account of those experiments, I felt almost sure, the expansion of the air in the earth, was the cause of earthquakes; though I did not exactly understand how it could be. I am much obliged to you for your explanation. _Mrs. B._ You are very welcome, my dear. You lately read an account of one of these dreadful convulsions of nature. Where did it happen?