To answer this, consult the ingineers, and those that make mines in the sieges of towns; they will acquaint us, that the effect of mines is produced in form of an inverted cone. And that a diameter of 30 miles, in the base, will require an _axis_ of 15 or 20 miles to operate upon that base, so as to shake it, at least. Now the vapours, or whatever power we propose to operate, according to the foregoing requisite, in order to form the appearance of an earthquake, must be 15 or 20 miles deep in the earth. But what mind can conceive, that any natural power is able to move an inverted cone of solid earth, whose base is 30 miles diameter, whose axis 20? or was it possible; would not the whole texture of that body of earth be quite disturb'd and shatter'd, especially in regard to its springs and fountains? but nothing like this is ever found to be the consequence of an earthquake, tho' fatal to cities. Apply this reasoning to the earthquake of _Asia minor_, and this vigorous principle at the _apex_ of the cone must lie, at least, 200 Miles deep in the ground. Enough to show the absurdity of any moving power plac'd under the Earth! A cone of 300 miles diameter at base, 200 miles _axis_: I dare be bold to say, that all the gun-powder made since its invention, if put together and fired, would not be able to move it; how much less pent up vapours? what must we say of a circle of 900 miles diameter? But, could that be admitted as possible, would any one be persuaded, that such a subterraneous tumult, of so vast an extent, will be no ways injurious to the internal system of springs and fountains, and that this shall often be repeated without the least damage? We may as well imagine, that we can stab a man 100 times and never touch vein or artery. Since I gave in my two papers to the Royal Society, a letter of Mr. _Flamsted_'s has been printed, which abundantly confirms my sentiments. The whole drift of it is, to show how invalid is the vulgar idea conceiv'd, of earthquakes arising from subterraneous vapours and eruptions: That the earth itself is not moved to any depth, and that the shock must arise from the atmosphere. The circumstances which he has judiciously collected, are extremely agreeable to mine; many of them the very same, strongly confirming my _hypothesis_: And had that great man known the properties of electricity, which we are now masters of, he would have prevented me in this affair.