too sensibly felt; to the destruction of many thousands, by their pestiferous qualities.
Indeed this consideration alone, of the extent of that surface, is sufficient to overthrow any supposition, of earthquakes being chiefly owing to subterraneous vapours: They cannot momentarily fly under so large a tract of ground, if they were near the outward shell of the earth. They could not do it without breaking ground, and discovering themselves to the sight, or smell; and that for a long time after. It cannot possibly be imagin'd, they should have so immense a force, as to lift up the city of London, and never be perceived by our organs, and outward senses. We have frequent accounts of a little fire-ball burning in the air, at a distance; yet it instantly propagates a sulphureous smell around.
If the movement of a superficies of 30 miles diameter was owing to fumes, and vapours; we ought reasonably to find some great discharges of them, belching out smoke and fire, for a long time after, like vulcano's, and coal-pits fir'd. The operation of the shock ought to be of hours continuance, not instantaneous; and the evaporation of so vast a quantity of matter, must darken the whole region of the air for a long time after; or require a long time, if gradually it discharges itself. We see how immense a volume of smoke is produc'd