We never hear, from the many hundreds of thousands of workmen in this kind, at _Newcastle_, _Nottinghamshire_, _Yorkshire_, _Derbyshire_, _Staffordshire_, _Somersetshire_, and _Wales_: from the infinite numbers of workmen in the mines of lead, tin, and the like, of the cavernous state of the earth, so as to give any colour for this _hypothesis_ of earthquakes. The earth is generally of solid rock; in which there must be now, and then, some clefts, and vacuities, small in compass, as naturally so many heterogeneous _strata_ of the earth consolidate together. But there can be no imagination of vapours breaking through, uniting, traversing so suddenly, a large space of earth, so as to produce those earthquakes, we have seen, and felt; much less such as we read of. The workmen in all sorts of mines confess by their hard labor, that the earth is not cavernous; nor are there mines of sulphur, nitre, and the like inflammable materials in _England_. Or if there were, could they burn, and cause convulsions of the earth, without proper cavities, pipes, and conveyances of air; as vulcano's, and coal-pits, when set on fire. But even from these coal-pits, when fired, do we ever find any thing like an earthquake produced. Nor do we find earthquakes frequent in those countries, that abound with coal-mines, as certainly would be the case, if that _hypothesis_ was just. How easy would it be, on the slightest occasion for earthquakes to happen in the countries abounding with coal-mines, which are so full of artificial cavities communicating with one another, for many miles together: The very thing supposed, by those who hold the old opinion, of vapours traversing the earth for that purpose. In the coal-pits, some small natural cavities now and then are found; which when opened, send forth a pestiferous vapor and a fire-damp which runs for a long time together. And tho' there are many substances that may generate air, within the bowels of the earth; yet these matters are infinitely unable to produce an earthquake: Never would have force to open a passage for themselves thro' the solid rock, of perhaps many hundred feet in thickness. Nor did we observe in these last earthquakes any fire, vapour, smoke, or smell, any kind of eruption, in the least; as must certainly have been, in so great a struggle of the superfice, as affected a circle of so large a diameter. Were there such, we could scarce hope any otherwise, than that they would be too sensibly felt; to the destruction of many thousands, by their pestiferous qualities.