In the gravelly soil of _London_; and where the two shocks were felt by us, in the beginning of the year; we know, there is not a house in the whole extent of this vast city, and all around it, but a spring of water is ready, upon digging a well, Whence we have much reason to believe, that the interior of the earth, is like a sponge soak'd in water. So that the only dry part is the superficies, which is the object, and the subject of that electric vibration; wherein, according to my sentiments, an earthquake consists. This shews the mistake of the ancients, who fancying that earthquakes proceeded from subterraneous eruptions, built their prodigious temple of _Diana_ at _Ephesus_, upon a boggy ground, to prevent such a disaster, The marshy part of _Lincolnshire_, being my native country, the adjacent fen, together with that in the isle of _Ely_, I have been perfectly acquainted with; from one end to the other, ever since I knew any thing. This vast extent of fenny level, from near _Cambridge_ in the south, to near _Horncastle_ in the north, is 70 miles in length. And when I perceiv'd, that it was, in whole, or in part, shaken by both the last earthquakes: I could not but see, that it was no less than a demonstration against the old notion of their cause. 6ly, Earthquakes are truly most violent, in a rocky country: because the shock is proportionate to the solidity of the matter electrify'd. So that rocks, cliffs, quarries, old castle walls, and strong buildings, are most obnoxious to the concussion. The isle of _Cerigo_ was more liable, and more rudely handled by the late earthquake; both because it was an isle, and because it was rocky. So we must say of the late earthquake in _Switzerland_, that split the mountain, and the old castle wall. Whence Mr. _Johnson_ in his second letter, says, it cracked a very strong brick-house in _Gosberton_ by _Spalding_. Dr. _Doderidge_ observes from _Northampton_ that Dr. _Stonehouse_'s dwelling being a very strong one, was most sensibly shaken. And throughout the whole compass of this great earthquake, we find, both the noise, the shock, and the terror was greatest at the churches, whose walls and bulk made more resistance than houses. And generally speaking, the churches throughout this whole extent have very fair, and large towers, and very many remarkable spires all of good stone, which no doubt quiver'd very much at top, if we could have discern'd it. This same vibration impressed on the water, meeting with the solid of the bottom of ships, and lighters, gives that thump felt thereon; just as in common electrifying, we feel the stroke upon the joints of our limbs chiefly. Yet of the millions of ordinary houses, over which it passed, not one fell. A consideration which sufficiently points out to us, what sort of a motion this was not, what sort of a motion it was, and whence deriv'd; not a convulsion of the bowels of the earth, but an uniform vibration or undulation of its surface, aptly thought