Philosophical transactions, Vol. L. Part I. For the year 1757. / Giving some account of the present undertakings, studies, and labours, of the ingenious, in many considerable parts of the world.

by Various; Royal Society

Reverend Sir,

Read Jan. 13, 1757.

I Beg leave to lay before you the best account I am able to give of the great earthquake, which shook New England, and the neighbouring parts of America, on Tuesday the 18th day of November 1755, about a quarter after four in the morning. I deferred writing till this time, in order to obtain the most distinct information of the several particulars relating to it, both here and in the other places where it was felt; and especially the extent of it.

The night, in which this earthquake happened, was perfectly calm and serene. In the evening there was a fog over the marshes bordering on the river Charles, which runs through this town: but this I found intirely dissipated at the time of the earthquake, the air being then quite clear, and the moon, which wanted but 36^h of the full, shining very bright. The earthquake began with a roaring noise in the N.W. like thunder at a distance; and this grew fiercer, as the earthquake drew nearer; which was almost a minute in coming to this place, as near as I can collect from one of my neighbours, who was then on the road in this town. He tells me, that, as soon as he heard the noise, he stopt, knowing, that it was an earthquake, and waiting for it; and he reckoned he had stood still about 2', when the noise seemed to overtake him, and the earth began to tremble under him: but, as I doubted, whether it were so long, I counted several numbers to him as slowly as a clock beats seconds; and then he said, he believed he could have counted half an hundred, at that rate, before the noise and shake came up to him. By his account, as well as that of others, the first motion of the earth was what may be called a pulse, or rather an undulation; and resembled (to use his own comparison) that of a long rolling, swelling sea; and the swell was so great, that he was obliged to run and catch hold of something, to prevent being thrown down. The tops of two trees close by him, one of which is 25, the other 30 feet high, he thinks waved at least ten feet (and I depend on his judgment in this particular, because he judged right of the height of the trees, as I found by actual mensuration); and there were two of these great wavings, succeeded by one, which was smaller. This sort of motion, after having continued, as has been conjectured, about a minute, abated a little; so that I, who was just then waked, and, I suppose, most others, imagined, that the height of the shock was past. But instantly, without a moment's intermission, the shock came on with redoubled noise and violence; though the species of it was altered to a tremor, or quick horizontal vibratory motion, with sudden jerks and wrenches. The bed, on which I lay, was now tossed from side to side; the whole house was prodigiously agitated; the windows rattled, the beams cracked, as if all would presently be shaken to pieces. When this had continued about 2', it began to abate, and gradually kept decreasing, as if it would be soon over: however, before it had quite ceased, there was a little revival of the trembling and noise, though no-ways comparable to what had been before: but this presently decreased, till all, by degrees, became still and quiet. Thus ended this great shock. It was followed by another about an hour and a quarter after, viz. at 5^h 29'. This, though comparatively small, was very generally perceived, both as to its noise and trembling, by those who were awake. On the Saturday evening following, viz. the 22d of November, at 27' after eight, there was a third, more considerable than the second, but not to be compared with the first. And on Friday the 19th of December in the evening, exactly at ten o' clock, there was a fourth shock, much smaller than either of the former, though, like them, preceded by the peculiar noise of an earthquake. The whole lasted but a few seconds; but the jarring was great enough to cause the window-shutters and door of the room, in which I then was, to clatter. The sky was perfectly clear, and there was a very gentle and scarcely-perceptible gale at S.W. These four are the only shocks, that I have been sensible of from the 18th of November last to this date; tho' more are said to have been felt in other parts of the country to the northward of us.

As to the duration of the great shock, people have differed widely, viz. from 1' to 6 or 7. Our printed accounts have generally fixed it to about 2', or 3 at the most; but as these were only the uncertain guesses of persons, who had no rule to guess by, no dependence can be had on them. I am well satisfied, that with us it continued 4', or rather 4' 1-half; taking in the whole of the time, from the first agitation of the earth till it was become perfectly quiet; tho' the violence of the shock did not last above half so long. This I am assured of, partly from the observations of some gentlemen, who were up, and looked on their watches, when it began and ended; one of whom tells me it was 4', and another, that it was near 5; and partly from my own observations, which were as follow. The preceding noon I had adjusted both my clock and watch to the apparent time, by a meridian line; and the following noon I found, that the watch had kept time exactly. Being awaked by the earthquake, I lay till the violence of it seemed to be over for the second time, the first abatement happening just after I waked. Till then I forbore to rise, because the agitation was so vehement, that I concluded it would be difficult, if not impracticable, to go from the bed to the chimney, without being thrown down; and therefore thought it best not to attempt it. The space of time, in which I lay awake, I cannot think to be much, if any thing, less than 2'. This was the conjecture I formed at that time; though, it being but conjecture, I would not lay very great stress upon it, were it not supported by concurring observations. On the second abatement I rose, and lighting a candle, looked on my watch, and found it to be 15' after four. The shock then was not quite over, but the windows continued rattling for about a minute longer, as near as I can remember; for the shock went off very gradually. As soon as I had looked on the watch, I went directly to the clock, which was in another chamber, that I might see whether that agreed with the watch, and found that it was stopt at 4^h 11' 35''. Its stopping, however, was not immediately owing to the violence of the shock, though several clocks, and watches too, at Boston, are said to have been stopped by it, but to the following accident: Having some time before used a pretty long glass tube, in a particular experiment, I had shut it up in the clock-case for security; and this tube, being overthrown by the earthquake, lodged against the pendulum, and stopt its motion. By this accident, the beginning of the earthquake, I conceive, is determined with all the exactness, that can be desired; for, so far as I can learn, the first shake was violent enough to overset so tall, slender a body, and standing in a position so near a perpendicular, as that tube; and it was impossible for the pendulum to make one oscillation, after the tube had struck against it. But I am not able to fix the end, nor consequently the duration, with the same exactness: however, from the time, when the clock stopt, to my looking on the watch, it was about 3' 1-half; and the jarring was not quite over till about a minute after this: so that I think I speak within bounds, if I say, that this shock with us lasted at least 4'. In other places, its duration might possibly be different. I was careful to note the time, when we had it, as exactly as I could, in hopes, that, by comparing it with the like accounts from distant places, we might be able to judge, with a good degree of exactness, of the course of this earthquake, the place of its origin, and the velocity of its progress. But all the accounts of the time, which I have yet seen, are so very lax, that no just conclusions can be drawn from them, with respect to either of these points. What I have been able to collect with relation to them, I shall set down presently.

Those, who suppose the duration much shorter, as 1' 1-half, or 2', urge, that a minute is a longer space of time than most people are aware of; which is very true: but it should also be considered, that if we judge the length of any space of time by the number of ideas, which pass through our minds in that time; a very great fright,—a fright so great, as to take intire possession of the mind for a time, and shut out every idea except that of the present danger, will make us judge the time to be much shorter than it really is. And this, I make no doubt, was the case with many; the surprise, into which they were thrown, being such, as to keep out every idea, except that, which happened to strike their minds with the greatest force at the beginning. Thus, several perceived no noise distinct from that, which was occasioned by the crackling of their houses, and the disturbance of the moveables in them; while others, who were waked by the noise, and ran from one room to another, have told me, that they felt nothing at all of the shake. For this reason, the conjectures, which persons in these circumstances made, as to the duration of the shock, ought not to be put into the balance with the actual observations made by watches.

The course of this earthquake seems to have been nearly from N.W. to S.E. My neighbour before-mentioned, who was then abroad, and informed me, that the noise began about the N.W. told me at the same time, that it passed off towards the S.E. and that he heard the noise in that quarter gradually abating, as it became more distant, for about the same space of time after the shock was over here, as he heard it in the N.W. before the shock began here. Other accounts, which I have since met with, agree with this. Those, who were in such clear open places, could make the best judgment in this matter; for such, as were within doors, or surrounded with buildings, might easily be misled by the various reflections of the sound. I am induced to give the greater credit to this information by what I observed myself: for a key, which was thrown from off a shelf in my house, was found at a place on the floor, which bore very near N.W. of the place, from which it fell; though the situation of it before its fall was such, that it might have been thrown in any direction, except towards the S.E.

An account, which we have lately received from the West-Indies, agrees very well with the supposition, that our earthquake proceeded south-eastward. The account is, that 'on the 18th of November, about two o'clock in the afternoon, the sea withdrew from the harbour of St. Martin's, leaving the vessels dry, and fish on the banks, where there used to be three or four fathom water; and continued out a considerable time; so that the people retired to the high land, fearing the consequence of its return; and when it came in, it arose six feet higher than usual, so as to overflow the low lands. There was no shock felt at the above time.' As this extraordinary motion of the sea happened about 9^h after our great shock, it seems very likely to have been occasioned by the same convulsion of the earth. Now if this earthquake went off south-eastward into the Atlantic, it must have passed considerably to the eastward of St. Martin's; and, in fact, it did not reach that island, there being no shock felt there. The motion of the sea then was owing to a great agitation raised at a considerable distance in some part or other of the ocean, where the earthquake passed, and from thence propagated to that island. Nor is the length of time greater than what seems to be necessary for this effect. The earthquake itself, at the rate it moved with us, would be some hours in going from hence to the distance of St. Martin's: for sound would be about 2¼^h in moving to such a distance; and the progress of the earthquake was slower than that of sound, as appears from hence, that the roar of this earthquake arrived here near a minute before the shake. The rest of the 9^h might well be spent in conveying the motion excited in the water, from the place where it was excited, to St. Martin's; for the waves raised thereby could not move with near the velocity of sound.

It is worthy of remark, that, of the five great earthquakes, which this country has felt since its settlement by the English, two have gone nearly in the same track as this last did. The first, which was on June 2. 1638, 'came from the northward, and passed southward.' By the description given of it, it was very much like our late earthquake, only perhaps not quite so violent. 'The noise and shakes of the earthquake, October 29. 1727, seemed,' it is said, 'to come from the north-westward, and to go off south-easterly; and so the houses seemed to reel.' As to the great earthquakes of 1658 and 1662, we have no account of the courses, which they went in. But, from the other three, it may be reasonably conjectured, that the source of our earthquakes, or the place in which they originate, is in some part of Canada, or perhaps beyond it.

The extent of this earthquake seems to have been greater than that of any of our former earthquakes. This province of the Massachusetts-bay, or rather the province of New Hampshire, about the latitude of 43° north on the sea-coast, seems to have been the center of it, or the place of its greatest violence, and the shake to have been less considerable each way from hence towards the S.W. and N.E. By the accounts we have from the S.W. the shock was less at New York than it was with us; and still less at Philadelphia, which is farther towards the S.W. By the best information I can procure, the limit toward the S.W. was Chesopeak-bay in Maryland, the shock having been felt on the eastern side of that bay, and not on the western. For the other limit toward the N.E. we are informed, that the earthquake was felt at Annapolis Royal in Nova Scotia, though in a much less degree than with us. It shook off a few bricks from the tops of some chimnies, but was not perceived by vessels on the water. And a letter from Halifax says, 'The earthquake, which happened in the W. extended itself to this place, tho' scarcely perceivable here.' But it was not at all felt by our army, which lay encamped at Seganecto, about 100 miles N. from Halifax. Thus Halifax seems to have been very near the N.E. limit. I am not able to ascertain its eastern and western limits; but it extended to all our back inland settlements; and was perceived, though in a very small degree, by our army at Lake George, distant from hence about 130 miles N. W. by W. But it was not felt at all at the British fort of Oswego, situate on the south-eastern shore of Lake Ontario, and distant from hence about 230 miles W. by N. So great was the shock in the Atlantic, 70 leagues to the E. of Cape Anne, that the people on board a vessel there were suddenly surprised, just at the time of our earthquake, supposing they had run a-ground; till, on throwing over the lead, they found they had more than 50 fathom water. The extent of the earthquake E. and W. from Halifax to Lake George was about 550 miles; and its extent along the sea-coast, from N.E. to S.W. at least 800 miles. But if the agitation of the water at St. Martin's was occasioned by our earthquake continued into the Atlantic, as was conjectured above, its extent, in a direction toward the S. S. E. must have been at last 1900 miles.