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whose spring, compressed in a little room, will not only shake the superior ground, but seek for passages whereby to extricate itself: such are the canals formed by subterraneous rivulets, where a furious wind will be formed, whose noise will be heard at the earth's surface; and this wind will throughout its whole extent cause an carthquake, more or less violent, in proportion as it is more or less remote from the new kindled 'fire, or rushes through passages more or less narrow.
This explication seems to agree with the several phenomena of earthquakes.
Chymistry furnishes a method of making artificial earthquakes, whose effects shall be in all respects similar to those of the natural ones; as it fully illustrates the process of nature upon the very principles I have advanced, I here give it, though pretty well known, from Boerhaave.
To 20 pounds of iron filings, add as many of sulphur; temper, mix, and knead the whole with a little water into a stiff mass, which bury some feet deep in the ground. In six or seven hours time this will produce a prodigious effect; for the earth will begin to tremble, crack, and smoak, and actual fire and fame will at length burst through. Such is the effect of two cold bodies in the cold ground, from the bare intermixture of a little water: there wants but a suificient quantity of the mass to produce a true volcano.
It has been observed for ages past, that places near the sea are the most exposed to the térrible disasters of earthquakes, on which account, doubtless, it was that Neptune was called by the ancients Σασίχθων, as also Κινοσίχθων, Εν σίgana and Tovcerdogoyaens, by all which epithets they denoted his power of shaking the earth. Cast your eyes to those parts of the globe where volcanos most abound, and you will find them all situated in islands, or near the sea coast, and where these are earthquakes are frequent. The Alps are not subject to them, but those parts of Italy which are farthest advanced into the Mediterranean are; and the like holds good in America.
The season of the year seems to have some share in these tremendous events. The first great overthrow of Liina was indeed in July 1586, but the other two of 1687 and 1740, fell out both in October, probably after the equinoctial high tides, in conjunction with the western winds, had introduced much water into the subterraneous cavities. Lima has been considerably shaken by two other earthquakes in 1630 and 1655, both which, like the late dreadful one at Lisboni, were in November.
XX. Account of a moving Hill.
MR. URBAN GIVE me leave, by your means, to communicate to the public what seems highly to deserve their notice, and what you may depend on tlie truth of, having been myself an eye witness.
At a place called Toys Hill, about three miles from Westran in Kent, about two acres and a half of ground (part ploughed and part turnips) has since Christmas last undergone a great and surprising alteration. The situation is on the side of a hill, inclining to the south, and the land has been continually moving in that direction, imperceptibly indeed at the time, but now the effect is very apparent. The upper or northern side, now planted with turnips, is sunk two or three feet, and is full of clefts or chasms, some of them a foot deep, and many of them filled with water. Two or three are as large as ponds, being six or eight feet deep, and ten or twelve square. Part of a hedge, which divided the fields is moved about three roods to the southward so as to form an angle with the two ends which it was upon a line with before. Another hedge is broke asunder, and there is now a gap of eight feet where before it was contiguous. Between the fields is a large coppice, which is also full of cracks and pits of water, and a large oak therein is apparently falling. The southern part which has been ploughed this winter, and was then on a level with the rest of the field, now overhangs it like a precipice about the height of twelve feet, and is rendered quite useless for the purpose of sowing, as is all the rest for pasture or tillage. That land on each side which has not moved, is covered by the rest, which folds over it at the height of six or seven feet.
Numbers of people daily resort to see it, and where it will end nobody knows, as in two or three days time, especially after great rains or snows, fresh alterations are still perceived. The History of England makes mention of a similar' case happening at Westran in the reign of Queen Elizabeth.
As the best verbal description must be inadequate, if this imperfect one should induce some of your ingenious correspondents to visit the place, and take a sketch of it in its present form (and I assure him the strangeness of the sight will highly reward his trouble) it might further contribute to the satisfaction of your readers, and thereby answer the design of your constant purchaser,
Though a physical solution of the appearance at 'í'oy's Hill, as described by you in last Magazine, mirznt come more plausibly from one that had had an opporcunity of inspecting it, and that something perhaps might be gathered from the nature of the stratum in the part described; yet I shall venture to offer you a hint concerning the cause of the ambulation of this portion of solid earth, not only not inadequate to the tact, but also confirmed, as I think, by experience. I suppose then there must be an even and smooth layer of some kind, probably of clay, underneath this floating field, to the North at the depth of three feet, and to the South at the depth of twelve, with a small rein of water upon its surface, just enough to moisten it. Now as the last summer was remarkably wet, and the winter rather so than otherwise, and the declivity of the hill would give a propensity to slide, a very small matter, it is apprehended, in such circumstances, might serve to put the mass in motion; and when I consider, that an earthquake was felt in the South of England, on the 1st of November last, I incline to believe, that the concussion of this island, though so slight, might be sufficient to set this ground in motion. This is my conception of the matter; and I think it greatly supported by an incident at Pillingmoss, in Lancashire, and the reason commonly assigned for that; 'In February 1745, on the East side of Corlew Hill, a part of Pillingmoss floated down Danson's, or Wild boars dales, and drove before it a vast quantity of mud, loose turfs, and black water, and covered with that kind of matter near 50 acres of ground (almost 20 of which was improved ground) to a great thickness; and sliding on, it reached as far as Dr. Danson’s house, and pressed it down.' This account I have from a pamphlet published on the occasion, where it is observed there had happened two such slips of the same moss hefore, one that the author had seen about the year 1708 or 1709, and another which he had heard of from old people. The fluxion of the moss was very slow, on account of the thickness of the matter, though the said matter was in a liquid
state ; but the matter floating at Toy's Hill, being more fixed, one has reason to expect it would be stili sio.er, as we find it was, to wit imperceptible. There wis a declivity in both cases, and in both much rain had fallen, to facilitate the defluxion; for as to the cause of the motion at Pillingmoss, it is entirely attributed to the abundance of rain and snow that had fallen, and had softened st, upon which it was very natural for the liquified matter to descend and slide, upon the clay underneath, from a higher to a lower place; I see no difference in the two cases, only that here the sliding matter was liquid, whereas at Toy's Hill it is fixed; but this will make no alteration in
other respect, but in the beginning of the motion; the moss would slide in its own nature, as a fluid, but the field at Toy's Hill would require a first mover, and this, as was mentioned, I take to have been the earthquake.
Yours, &c. 1756, March and April.
40orum sonim toto Germania cælo
Virg. Georg. i. 474, MR. URBAN, IT is a vulgar opinion, that the Aurora Borealis, or the northern lights, were never seen in England till the 6th of March, 1715. Indeed the lights that appeared then were very extraordinary, and happened at a very critical time, which occasioned their being much taken notice of, as also their being mentioned by our historians, * to which I may well add, that none so copious or remarkable had probably happened for many years before. It is not my present business to inquire into the cause of this phenonienon, which may be learned from other authors, + but for the rectifying this mistaken notion of their first appearance, which can tend to nothing but superstition, as generally all philosophical errors do, I shall recite a few examples of their being observed in this nation long before the date abovementioned, even before the Norman Conquest, to which period I shall at this time confine myself.
* Salmon's Chronolog. Hi-torian. Whiston's Memoirs, p. 608. &c. + Dr. Hailcy, in Phil. Trans. Dr. Gawin Knight, on attraction and repule sion.
The first example I meet with is A. D. 555, when as Matth. of Westminster relates it; quasi species lancearum in aëre visæ sunt a Septentrione usque ad Occidentem,' that is, certain appearances of lances were seen in the air from the north to the west. * Whereupon you will please to observe, that these coruscations were in the northern parts of the world, I presume, chiefly in the north-west, and that the people called the streamers lances, as they did in the year 1715.
The same author tells us, that in 567 ' Hastæ ignea in aëre visæ sunt, portendentes irruptionem Longobardorum in Italiam,' that is, that fiery spears were seen in the air, portending the incursion of the Lombarys into Italy. The notion of arms still prevails, the radiations being here called spears; and moreover they are supposed to be predictive of a grand future event, as on other occasions these lights are generally supposed to be, which calls to my mind that line in the first Georgic of Virgil, which I have chosen for the motto of this paper, where the poet enumerating the seve, ral prodigies that preceded and betokened the death of Julius Cæsar, mentions a sound of arms in the sky,
Armorum sonitum toto Germania cælo
which noise or clashing of arms was heard, you observe, not in Italy, but in the more northern regions of Europe.
Matth. of Westm. remarks again on the year 74%, Visi sunt in aëre ictus ignei, quales nunquam mortales illius ævi viderunt, Kal. Jan.' that on the first of January, certain fiery streamers were seen in the air, such as the men then living had never beheld before :t and then he immediately subjoins, that the same year Wilfred, Archbishop of York, died, as if he intended it to be understood, that these lights then portended his death.
In the year 776, Matthew writes, “Visa sunt in cælo rubra signa, post occasum solis, et horrenda,' that in the evening red signs, and horrible to behold, were seen in the
* Matth. Westm. p. 101.
f Ibid. p. 140.