quadrangular, like grains of salt; which made him suspect, that these petrifications contain, besides metalline, a great deal of saline particles, whose sides being strongly attracted to each other, and closely joined, hinders the fire from expanding the pores of these stones, and their being reduced to line. This black stone, when broken, appears through the microscope very beautiful, and like cloth of silver, the pores and vessels of the wood being filled with white minute crystals.

Of these stones Mr. S. had some with wood outwardly continuous; others with wood inwardly; one, the least, part is of stone, the rest wood; another vice versa; another entirely wood, except a thin coat of stone on one side, which appears to be the very bark; one stone which at one end distinctly shows the annual ringlets of the wood; one that shows the wood, before it was petrified, had been bent, and partly broken, the fissure being filled with a sparry matter, and appears plainly from the present appearance and position of the fibres of the stone. Some of these stones strike fire with a steel, and others by a strong collision, emit a train of sparks. Some of these stones show the grain of holly, ash, and fir. He had only one piece of oak petrified, easily distinguished by its grain; it shows the very knots of the wood where young twigs were cut; and has a hole made through it before it was petrified.

As for these stones being fit for sharpening or setting of razors, &c. the black ones are rather too hard, and the white ones too soft. The whetstones or hones, vulgarly so called, which are sold for Lough-Neagh stones, are none of these, but of a soft gritty kind, and found near Drogheda.

When these stones with wood continuous are taken out of the water, mud, or clay, the woody part dries, cracks, and falls away; which is the reason why few can be well preserved; and besides, every body, unwilling to trust their eyes, will touch and scrape the wood, aud thus destroy the most curious part of the stone.

[Phil. Trans. Abr. 1746.]

We have copied the preceding paper, not more for the curious and unquestionable fact it contains, than to exhibit a proof of the infant state of mineralogy not longer ago than the middle of the last century. The above paper is succeeded in the same excellent journal by another on the same subject, furnished by the justly ce

lebrated Dr. George Berkeley, Lord Bishop of Cloyne, who in the course of his theory to account for the petrifying property of the lake, gives us his opinion that stones are unorganized vegetables, formed by an accretion of salts; which he urges in opposition to those of his own age, who conceived stones to be organized vegetables produced from seeds. Waters impregnated with calcareous earth, and other petrifying materials, and productive of all the effects here spoken of with astonishment, are now known to be frequent iu most parts of the world: one of the most curious examples, in point of picturesque scenery, is perhaps the Dropping-well at Knares borough; and we have already noticed a similar property in several other waters, especially in the lake of Solfatara in Campagna. [EDITOR.]

SECTION XI.

Inundations.

We have already observed that many of the large rivers of the east, as the Nile, the Ganges, and the Indus, are subject to periodical exundations, and have pointed out some of the more ob vious causes of such an effect. There are others, however, that are subject to occasional overflows, and in many instances from causes that are altogether concealed. Among these we may perhaps enumerate the inundation of the Thames, about the year 1705, at Dagenham and Havering marches in Essex, which made an excavation nearly twenty feet deep, and laid open a great number of trees, mostly alder, buried under a soil obviously composed of the mud of the Thames, and which had, in all probability, been overthrown by some previous inundation of a similar kind.

The following, in the island of Mauritius, is to the same effect: On the 22d of March, 1696, observes Mr.Witsen, at half an hour after twelve o'clock, being calm but a little rainy, the river which passes by the plain ground of Noardwyek, in the space of a quarter of an hour swelled to such a height, that the sugar-mill, the sugar-work, and almost all the said ground was ruined, the most part of the sugar-canes being rooted or torn out of the ground by the violence of the torrent. It cannot be imagined what had caused so sudden a swelling of this river, for the rain was not very hard, and could not have produced that effect; for about twelve o'clock, when the com

pany's servants assembled for dinner, the water of the river was at its ordinary height, and before they had half dined all the country was flooded a foot higher than two years since, when there was a hurricane and a most violent storm. It is very remarkable, that at one o'clock all the extraordinary water was gone, and the river again at its ordinary height. There has been no earthquake that could cause it, neither was there any such thing in other rivers.

In other instances the cause is peculiarly clear, though the vio lence with which it operates, is most ruinous and astonishing. The following is a case of this kind that occurred in the valley of St. John's, near Keswick in Cumberland, August 22, 1749. We take the account as published in the Phil. Trans. for 1750, and com. municated by John Lock, Esq. F.R.S.

This remarkable fall of water happened at nine o'clock in the evening, in the midst of the most terrible thunder, and incessant lightning, ever known in that part in the memory of the oldest man living, the preceding afternoon having been extremely hot and sultry. And what seems very uncommon, and difficult to account for, the inhabitants of the vale, of good credit, affirm they heard a strange buzzing noise like that of a malt-mill, or the sound of wind in the tops of trees for two hours together before the clouds broke. From the havock it has made in so short a time, for it was all over in less than two hours, it must have far exceeded any thunder-shower that we have ever seen. Most probably it was a spout or large body of water, which, by the rarefaction of the air, occasioned by that incessant lightning, broke all at once on the tops of these mountains, and so came down in a sheet of water on the valley below.

This little valley of St. John's lies east and west, extending about three miles in length and half a mile broad, closed in on the south and north sides, with prodigious high, steep, rocky mountains: those on the north side, called Legburthet Fells, had almost the whole of this cataract. It appears also that this vast spout did not extend above a mile in length; for it had effect only on four small brooks, which came trickling down from the sides of the rocky mountains. But no person, that does not see it, can form any idea of the ruinous work occasioned by these rivulets at that time, and in the space of an hour and half. At the bottom of Catcheety