in the same places, and often mixed with it, so much resembling it in appearance, as not, without some attention, to be distinguished from it; which however greatly differs from it in sensible qualities. Great care therefore ought to be taken, that the one of these should be selected from the other. The plant so much resembling hemlock, is the Cicutaria vulgaris of the botanists, which in some parts of England is called cow-weed, in others wild cicely. Its greatest resemblance to hemlock is in the spring, before the stalks of the leaves of the hemlock are interspersed with purple spots; and therefore at that season more easily mistaken for it; though even then the leaves of the hemlock smell much stronger, are more minutely divided, and are of a deeper green colour, than those of the cow-weed. Afterwards indeed they are more easily distinguished, as the Cicutaria flowers at the end of April and beginning of May, and the Cicuta not till June, when the other is past; to say nothing of the flowering stalk of the cow-weed being furrowed, and somewhat downy; and that of the hemlock, smooth, even, and always spotted. These plants differ likewise very essentially in their seeds, which in the cow-weed are long, smooth, and black, when ripe; whereas those of the hemlock are small, channelled, and swelling towards the middle.

Besides the cow-weed, there is another plant in appearance very like the hemlock, though evidently differing from it in other respects; and it seems quantities of this have been collected, and sold in London for the hemlock. This is more likely to be taken for the hemlock in summer or autumn, as it is an annual plant, and is produced and flowers late in the season. The plant here meant is the Cicuta minor of Parkinson, or Cicutaria tenuifolia of Ray. This however is easily distinguished from hemlock, by its leaves being of the colour and shape of parsley, its flowering stalks having no purple or other spots, and not having the strong smell peculiar to hemlock.

To the two plants before-mentioned, may be added a third, which very frequently, more especially about London, grows along, and is mixed, with the hemlock. This plant is called, by the late excellent Mr. Ray, Small hemlockchervil with rough seeds; and is denominated by Caspar Bauhin, in his Pinax, Myrrhis sylvestris seminibus asperis. This, like the cow-weed before-mentioned, can only be mistaken for hemlock in the spring. It may be distinguished then from it, by the leaves of the myrrhis being more finely cut, of a paler green cclour, and, though they have somewhat of the hemlock smell, are far less strong, and have no spots. This plant flowers in April, and the seeds are ripe before the hemlock begins to flower; and these seeds are cylindrical, rough, and terminate in an oblong point.

The leaves of hemlock are more fit for medical purposes, as being in their greatest perfection, when collected in dry weather, from the middle of May to

the time that their flowering stems begin to shoot; as by that time the plants will have felt the effects of the warm sun, have acquired a highly virose smell, and the stems of the leaves are covered with purple spots, an argument of the exaltation of their juices: and we should be attentive here to give them all these advantages, as 3 degrces of latitude, and other circumstances of soil and situation, may occasion a very sensible difference in the qualities of the same plant; an instance of which occurs in the plant under consideration, and may be one of the causes, why the effects of the hemlock have not been such here, as we are assured they are at Vienna; viz. Dr. Storke says, that the root of hemlock, when cut into slices, pours forth a milky juice, which Dr. W. had never seen it do here in England.

There are several vegetables which, though they thrive apparently well, their productions are yet not the same as in other parts of the world, where the heat is more intense, and the summers are of longer continuance. It would be extremely difficult here, though the plants thrive very well, to produce from the white poppy, or Cistus ladanifera, either the opium or the labdanum, the known production of these vegetables in other parts of the world. No art can make here the tragacantha pour forth its gum, the lentiscus its mastic, or the candleberry myrtle of North America its sebaceous concrete. To these might be added many others, too tedious to mention.

In such mild winters as the last, the leaves of hemlock may be procured in any part of them; but they are not to be depended on, as their specific smell is then comparatively weak, their juices poor and watery, and they are wholly without spots.

XVI. Of an Anthelion observed near Oxford, by the Rev. John Swinton, B. D. of Christ-Church, Oxon. F. R. S. p. 94.

Near the top of Shotover-hill, about 12m past 7 o'clock in the evening, Mr. S. accidentally discovered a luminous appearance, not much unlike the sun when seen through clouds, about 4 or 5 times as large as the solar disk. [See fig. 1. pl. 14.] The sun was then pretty resplendent, though a full exertion of its rays was somewhat obstructed by a thin waterish cloud. Soon after a very distinguishable Mock-Sun, opposite to the true one, which he took to have been an anthelion, appeared. This was not however completely formed, that part of its disk remotest from the sun being indistinct and but ill defined. Nor could the figure of the lucid tract round it, though approaching a circle, be with any precision ascertained. This uncommon meteor was seated in the E, but the sun had a westerly situation. From 7h 12m to 7h 18m the phenomenon shone very conspicuously, though almost surrounded by dark thickish clouds. The disk of the spurious sun seemed as large and bright as that of the true one, but was not so well de

fined. Between 7h 18m and 7h 28m the meteor was more than once partially obscured, by the circumjacent clouds; a very thick black one, which had been visible from the moment he first perceived the phenomenon, then extending itself almost from the western limb or edge of it to the sun. From the beginning to the end of the mock-sun's appearance, about 18m, there was much clear sky above the sun, even up to the zenith, and thick dusky clouds below it; but the tract both above and beneath the meteor was, for the most part, covered with such clouds. When in its most refulgent state, the anthelion was as yellow as the sun, but the lucid tract surrounding it was of a paler yellow, or whitish cast, interspersed with a few reddish and subfuscous spots. The whole, when least affected by the neighbouring clouds, seemed in extent to be 4 or 5 times the space occupied by the disk of the sun. In fine, the phenomenon was sometimes, brighter, and sometimes more obscure; varying, through the whole course of its duration, according to the variation of the atmosphere and the clouds. At last, after several short successive intervals of brightness and partial obscurity, it was absorbed by the black cloud above-mentioned, nearly connecting it with the sun; and about 7h 30m totally disappeared.

Instances of anthelia are extremely rare. Mr. S. had hitherto been able to meet with only 2 of them, viz. that observed near Dantzic by Hevelius, Sep. 6th, N. s. 1661; and that seen at Wittemberg in Saxony, Jan. 18th, N. s. 1738, a description of which was soon after communicated to the Royal Society by J. Frid. Weidler, Professor of Mathematics there.

XVII. On a Production of Nature at Dunbar in Scotland, like that of the GiantsCauseway in Ireland. By the Right Rev. Richard Lord Bishop of Ossory, F.R.S. p. 98.

The passage into the harbour of Dunbar is very narrow, between two rocks: one of them is the east side of the harbour; the other is a promontory, stretching out about 100 yards to the north, and is about 20 yards wide, having the sea on each side of it, when the tide is in. This head is a most extraordinary natural curiosity: it is of a red stone, which is not a lime-stone, but appears rather like a very hard free-stone. It looks on both sides like the Giant's-causeway in Ireland: the stones on the west side are from a foot to 2 feet over; on the east side they are large, from 2 feet to 4 feet. The pillars from 3 to 8 sides; but only one or two of the first and last: they may be said to be in joints, but are strongly cemented together by a red and white sparry substance, which is formed in laminæ round the pillars, and between the joints, 2 or 3 inches in thickness. The interstices between the large pillars, which are but few, are filled with small pillars, without joints. The pillars consist of horizontal lamina: the joints are not concave and convex when separated, but uneven and irregular: they lie sloping from

east to west on the west side, towards the end, the pillars become very large and confused, as those to the east of the Giant's-causeway, and in the isle of Mull; except that these are divided by such a sparry substance into a great number of small figures, which seem to go down through them. There are spots and veins of a whitish stone in the pillars. There is no sign of any thing of this kind in any of the rocks near, that he could observe, or hear of.

XVIII. Of a remarkable Meteor seen at Oxford. By the Rev. John Swinton, B.D., of Christ-Church, Oxon. F.R.S. p. 99.

On Sunday, Sept. 21, 1760, from 6h 49m to 7h 25m P. M. such a meteor appeared at Oxford as Mr. S. had never seen before. [See fig. 2. pl. 14.] A dark cloud, like a pillar or column of thick black smoke, and perpendicular to the horizon, appeared in the N. w. pushing gradually forward towards the zenith, and at last extending itself almost to the opposite part of the heavens. It was at first several degrees broad, but grew broader and broader, as it approached the zenith; through which it passed, and nearly bissected the hemisphere, in a wonderful manner. At 7h this surprising arch, falling little short of a semicircle, that would have resembled an iris, had not the colours of it been different, seemed to be completely formed. He says, "had not the colours of it been different;' because the lower part was exceedingly black, but the other subfuscus only and white. The exterior limb of this arch as far as the vertex was tinged with a pale yellow, that gave it no disagreeable appearance. The edges of it were at first tolerably smooth, and pretty well defined, but afterwards became rugged and irregular. The whole moved with the wind, from the first to the last moment of its existence. For a few minutes, it rendered the moon absolutely invisible. That planet had, for a considerable time before its approach, been somewhat darkened by the thick hazy air; which however did not totally obscure it. The tract near the northern part of the horizon, contiguous to the meteor, was interspersed with fuscous caliginous clouds, and that near the zenith with some of a whitish colour. All of them were very distinguishable from the phenomenon itself. They became gradually paler and paler, till they were entirely dispersed. About 7h 25m P. M. all remains of the meteor were so perfectly dissipated, that not the faintest traces of them were to be seen. That this phenomenon was a water-spout, or rather the first appearance of one, though the proper spout itself was not visible, will perhaps not be denied, Mr. S. says, by any person moderately versed in natural history. The weather was mild, or rather warm, the whole day. The wind, during the continuance of the phenomenon, and almost ever since, was w. s. w. though it did not then exceed a very gentle gale. Indeed the weather for 3 months before was, with very little intermission, hot and exceedingly dry, such as generally precedes meteors of this kind. As the phe

nomenon was seen by the Rev. Dr. Neve, Fellow of Corpus-Christi College, at Middleton-Stoney, 12 miles from hence, and at Sandford, N. w. of that village, a few miles farther from this place, at the very time that Mr. S. observed it, and attended by circumstances nearly the same with those that occurred to him; it must have been of a pretty considerable height. Mr. S. adds, that a most terrible storm of rain and hail followed it, which continued from a little past 3 to near 5 o'clock the next morning; and that they had much of such stormy weather there, and in the neighbourhood of that city long after.

XIX. On some Productions of Nature in Scotland resembling the Giant's-causeway in Ireland. By Emanuel Mendez Dacosta, F.R.S. p. 103. Mr. Murdoch Mackenzie, who, by order of the Lords of the Admiralty, surveyed the coasts of Scotland, communicated to Mr. D. the following. In Cana island, which is 4 English miles long, to the southward of Skye, and near the island of Rum, the rocks, about a quarter of a mile above the harbour, rise into polygon pillars southward. About 2 miles from the west end of Cana, is a low rock, or small island, where is a very regular pavement of hexagon stones, each about a foot deep, and about 9 inches over. They form a smooth uniform pavement; and the sides of all the stones lie extremely contiguous, or close. Immediately below this upper pavement, lies another exactly like it. The pillars are jointed exactly like those of the Giant's-causeway, and are laid with their concavities downward, and their convexities upward; and their hollows are as much in proportion to these pillars, which are smaller, as they are in those of the Giant's-causeway. These places are about 200 miles northward distant from the Giant's-causeway.

XX. Elements of New Tables of the Motions of Jupiter's Satellites. By Mr. Richard Dunthorne. Dated Cambridge, March 3, 1761. p. 105.

The public employment*, wherein I am at present, and for several years past have been engaged, not permitting me to make new tables of the motions of Jupiter's satellites, according to the last corrections I had (from a comparison of more than 800 observations) made in the places and orbits of those planets, I am at last persuaded to communicate to the Royal Society, the elements of those tables, hoping they will prove no unacceptable present to astronomers.

The tables are designed on the plan of those of Mr. Pound for the first satellite, published in the Philos. Trans. N° 361; except that I have not deducted the greatest equations from the epochs, as is done by Mr Pound. The epochs of the conjunctions of the several satellites with Jupiter, fitted to the Julian year (before

That of Surveyor to the Corporation of the great level of the fens.-Orig.

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