"Considering (says he) what variety of substances, sand, gravel, stones, rock, minerals, clay, and mold, our earth is compounded of, and how little nitre, or explosive matter, a large quantity thereof will afford; I cannot think, where we can find matter enough to move so vast a bulk of earth, as all the South parts of _England_, all the _Netherlands_, with part of _Germany_, all _France_, and perhaps _Italy_, (which were shock'd at once the 8th of _September_ last 1692;) or part of _Asia_, and near all _Europe_, which trembled together the same day, 91 years before. "But, allowing there may have been sufficient matter prepared for these purposes, I can hardly think, there are continued cavities, at any reasonable depth, all under _Europe_, wherein an explosion being made, might shake the whole at once, and yet make no clefts, or separations, in those parts where the minerals and mountainous rocks part from the light mold and clay. If an hundred barrels of gun-powder could be fixed in some cave, a thousand yards under ground; allowing the force of the explosion sufficient to raise all the weight of earth incumbent on the cavern; it would certainly break the loose mold from any large solid rock we may conceive adjacent, and leave at least some clefts behind it. But we seldom or never hear of such clefts, made in such places, when earthquakes happen." Again, he writes thus: "I cannot apprehend, (if all earthquakes must be made by explosions in subterraneous caverns) why sometimes a large country, or whole continent, should be thereby shook all at once; why there should be no eruptions in the neighbourhood?" From all circumstances consider'd, he concludes, that the abstruse, effective cause of them comes from the air; and that a calm is necessary before an earthquake. And these two particulars are likewise Dr. _Hales_'s positions: "The earth-lightning, as he calls it, is first kindled on the surface, and not at great depths, as has been thought; whose explosion is the immediate cause of an earthquake. He says, long, dry, hot seasons, are usually the preparatory forerunners of earthquakes." From all these considerations I conclude; earthquakes are not caus'd by subterraneous vapors. II. We are to inquire, what is the cause of earthquakes. In an age when electricity has been so much our entertainment, and our amazement; when we are become so well acquainted with its stupendous powers and properties, its velocity, and instantaneous operation through any given distance; when we see, upon a touch, or an approach, between a non-electric and an electrified body, what a wonderful vibration is produc'd! what a snap it gives! how an innocuous flame breaks forth! how violent a shock! Is it to be wonder'd at, that hither we turn our thoughts, for the solution of the prodigious appearance of an earthquake?