The gentleman who observed it about Hartingfordbury, says, the noise preceded the shock. And this is a common observation, which at once both strengthens our opinion of electricity, and confutes that of subterraneous vapours; for, in the latter case, the concussion must precede the noise.
Agreeable to out second position, Mr. Flamsted writes, "That earthquakes are felt at sea, equally as on land. Our merchants say, that, tho' the water in the bay of Smyrna lies level and smooth as a pond; yet ships riding there feel the shocks very sensibly, but in a very different manner from the houses at land: For they heave not, but tremble; their masts shiver, as if they would fall to pieces and their guns start in their carriages, though the surface of the sea lies all the time calm and unmoved." In Dr. Hook's Philosophical Collections, No 6. p. 185. we are told, "That a ship felt a shock in the main ocean; that the passengers, who had been asleep in their cabins, came upon deck in a fright, fearing the ship had struck upon some rock; but, on heaving the lead, found themselves out of soundings."
All this is extremely agreeable to our assumption. The water receives the electrical touch, and vibratory intestine motion of its parts, as well as land. And the impression may be made solely on the writer a non-electric, by the touch of an electric fire-ball, or the like; and that seems to have been often the care. The proper vibratory motion is impress'd on the water without ruffling its surface; and so communicated to all the parts of the ship, gives the sense of a shock to the bottom, the shivering to the mast, and the rest of the symptoms: which sufficiently proclaim the cause of it to be an electrical impression upon the water. The president mentioned a relation of a waterman, that felt it in his boat upon the river; he thought it like a great thump at the bottom of the boat. And so the ships at sea fancy, they strike upon a rock.
This makes us apprehend, the reason of the fishes leaping up out of the canal in Southwark, of which we had an account. So in that of Oxford, 1683, one fishing in the Charwell felt his boat tremble under him, and the lesser fishes seem'd affrighted by an unusual skipping. That electricity is the cause sought for, seems deducible from this consideration. Several writers on earthquakes assimilate these vibrations of the earth to those of a musical string. Experiments have shown, that fishes in water may be killed by the particular tone of a musical string; and 'tis known, that electricity will kill animals. They assuredly felt the vibratory motion in the water, which they were absolutely strangers to before. No doubt it made them sick; as those of weak nerves on land. And this circumstance alone precludes any suspicion of subterraneous fires under the ocean. Or, if we were to admit of it, would the boiling of the water exhibit any appearance, like what we are speaking of, either to the water, or to the ship?
Mr. Flamsted likewise concurs in our eighth position, "That many people found themselves suddenly sick at stomach, and their heads dizzy and light; so that those that had formerly fits of apoplexies, dreaded their return; particularly, one gentleman, a surgeon, feeling himself so affected, and fearing a return of his apoplexy, resolved to be let blood, without suspecting the earthquake."
After these two shocks which we felt, many people had pains in their joints and back, as after electrifying; many had sickness, headakes, hysteric and nervous disorders, and colicks, for the whole day after, and some much longer, especially people of weak nerves, weak constitutions; some women miscarry'd upon it; to some it has prov'd fatal.
To this we must attribute, that relation we had, of the dog lying asleep before the fire; but upon the earthquake, he suddenly rose up, run about the room, whining, and endeavouring to get out.
Any solid matter is capable of being put into a state or electricity, such as iron guns; and the more so, by reason of their solidity. And in proportion to it, is the greatness of the snap, and of the shock; and a kind of lambent flame issues from the point of contact; and likewise somewhat of a sulphureous smell: So that if both flame and smell were discernible in an earthquake; 'tis to be found, without going to the bowels of the earth.
Dr. Hales mentions, that solid bodies are the best conductors of aereal lightning; whence oaks are rent, and iron melted. And in our earthquakes in London, the loudest noise was heard near such large stone buildings, as churches, with lofty steeples. From the top of these we must apprehend, that the electrical explosion goes off into the open air; as in our experiments, from the point of swords, and the like.
The electrical shock is proportionate to the solid electrified, agreeable to our seventh position. This fully accounts for earthquakes in general, and for many in particular. What can be imagin'd greater than a shock of the body of the earth? 'Tis greater, or less in proportion to the state of electrification. And now we can account for several appearances. In the first earthquake, the Lord Chancellor, Masters in Chancery, and several Judges, were sitting in Westminster-Hall, with their backs to the wall of the upper-end, which is of a vast thickness. They all relate the severity of the shock, from the wall seeming to push towards them with great violence.