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tion, but the author hesitates to pronounce any decisive opinion as to the question, whether it approximates most nearly to the former or the latter class ; considering its characters as in many respects intermediate, and the combination of those characters as constituting a whole entirely sui generis.

In the course of this detail, the structure of the temporal fossæ, the parts surrounding the meatus auditorius, the posterior bones of the head, and the palatal and pterygoidal parts of the roof of the mouth, are minutely investigated.

Of the new Saurian genus Plesiosaurus (the discovery of which is due to the present author), the bones of the head which had not been discovered when the former communication was published, have since been procured. The teeth in this genus are placed in distinct alveoli, and in all respects resemble those of the crocodile; but in almost every other respect, the analogies presented by the head of this animal are much more closely allied with the lacertian genera.

The nostrils are small, and placed as in the Icthyosaurus ; so that the olfactory organs must have been much less developed than in any recent Saurians.

The comparativeshortness of the snout in the Plesiosaurus gives to the whole head a general character entirely dissimilar to that of the Icthyosaurus, yet many of its separate parts offer strong analogies with this genus also.

May 17.-Notice on a Fossil Bone found in the neighbourhood of Cuckfield, Surrey, by Capt. Vetch, MGS.

The bone mentioned in this notice was obtained from a bed of ferruginous sandstone, a short way north of Cuckfield in Sussex; this bed is 6 feet thick, resting upon blue clay, about 3 feet from the surface; and within the sandstone is a bed of limestone, about a foot thick; and the bone, under examination, was found at the upper junction of the limestone and sandstone partly imbedded in both. The bed of sandstone varies considerably in its thickness and dip; and the beds of limestone which it contains also vary in thickness and number. These two rocks contain vegetable remains, shells, and numerous small fragments of bone. That under notice is, however, of considerable size, but was evidently at the period of its envelopement in the sandstone, very imperfect.

The fact of the bones in this bed being so much broken and dispersed, would seem to show that they had been subjected to the action of some considerable force, probably of water; and as the fragments have not the appearance of being water worn, it may have been, that the bed of sandstone is not their original repository, but they had been lodged in a previous bed of sand or mud, till so far decayed as to be easily broken by slight forces. From the

appearance and internal structure of the bone under consideration, it may, the author conceives, be inferred, that it belonged to an aquatic animal, and if compared with the osteology of the whale, it bears some resemblance to the jaw of a small subject of that tribe, and still more to the rib of a large one. It is not improbable, however, that it has belonged to a genus very distinct from any we are now acquainted with. A smaller bone, procured near the same place, resembles part of the spine of a large animal, and may have belonged to the bone of the same individual with that in question.

Observations on the Strata of Tilgate Forest, in Sussex. By Gideon Mantell, Esq. MGS.

This paper is an abstract of a more detailed account which has, since the last meeting of the Society, been published in the author's work on the Geology of Sussex, and is intended merely to illustrate a series of specimens now presented by him to the Society

Notice on the Stonesfield Slate Pits. By Henry Hakewill, Esq. MGS.

The quarries from whence the specimens referred to in this communication were obtained, are in the village of Stonesfield, situated about three miles north-west from Woodstock, in Oxfordshire, on the north bank of the valley, in which the river Evenlode runs, and at a considerable elevation above the river. The strata from which the Stonesfield slates are made, occur at about 60 feet from the surface of the earth, and are worked by means of shafts sunk to that level, and the vein (as the bed sought after is called) is followed in an excavated gallery : the pendle, which is the name given to the bed from which the slates are made, consists of two distinct strata, separated by a gravelly vein of about a foot and a half thick called race; the upper course of the slatestone is about 10 inches in thickness, with excrescences of a circular form attached to it, called by the workmen bolt downs, or whims.

The lower stratum of the pendle is one foot thick, and upon its upper surface are excrescences of a similar form, called

caps. In the race are found numerous spherical nodules, flattened at the sides, six inches to four feet in diameter, but most commonly about two feet. Immediately above the pendle, there is occasionally a coarse stone, and in the pendle itself are found those interesting remains of animals, which have drawn the attention of geologists to this spot.

The slates are made from the stone dug in the summer, and brought to the surface, and spread out with the grain exposed to the weather; and, during the winter, it is frequently watered; the frost assists materially in dividing it into slates.

June 7.-A letter was read, accompanying specimens from Dr. Wallich of the Residency of Napal.

These specimens were brought from Mucktinath, a place at a distance of about 20 days' journey north-west from the valley of Napal, and probably at a very considerable elevation above it. They are said to occur always in the form of rolled pebbles, and to constitute almost entirely the bed of the river called Salagrami. The specimens themselves are of that sort which the Hindoos worship under the name of Salagrams; the present kind being called Shesha Kundala. They consist of

very

firm variety of a blackish argillaceous rock, and their form is that of ammonites in which they seem to have been moulded.

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ARTICLE XV.

SCIENTIFIC INTELLIGENCE, AND NOTICES OF SUBJECTS

CONNECTED WITH SCIENCE.

I. Definition of a Straight Line. A correspondent states that he shall feel obliged by any objection to the following definition of a straight line :

A straight line is such as being divided or produced to any extent, is still directed towards the same points.

II. Black Urine.

It appears from Dr. Marcet's paper in the Medico-Chirurgical Transactions, that he has met with some cases in which black urine had been voided. At the request of Dr. Marcet, some was examined by Dr. Prout, who gives the following account of its che:nical properties :

The residuum obtained from this urine by evaporation not only does not contain any lithic acid, as was observed by Dr. Marcet, but no urea can be detected in it by the tests which indicates its presence.

Although the addition of dilute acids produced no immediate change of colour in the urine, yet, on standing for some time, a black precipitate slowly subsided, leaving the supernatant fluid transparent, and but slightly coloured.

The black precipitate thus obtained was found to be nearly insoluluble either in water or alcohol, whether hot or cold. It readily dissolved in cold concentrated sulphuric and nitric acid, forming a deep brownish-black solution ; but, on diluting the acids with water, the black substance appeared to be again precipitated unaltered. These acids, however, by the assistance of heat, apparently decomposed it. The black substance readily dissolved in the fixed alkalies and in the alkaline subcarbonates, forming very dark solutions. The addition of water did not affect these solutions ; but acids re-precipitated the substance apparently unchanged. When ammonia was employed as the solvent, and the excess expelled by evaporation to dryness, a black or deep brown residuum was obtained, which appeared to be a compound of the black substance with ammonia, and possessed the following properties :

It was very soluble in water; and, on being heated with caustic. potash, it gave off the smell of ammonia. The black compound, however, did not appear to have any tendency to assume the crystalline form.

In evaporating to dryness, on a piece of glass, the ammoniacal solution in which the black substance had been dissolved, the residuum split into most minute fragments, having a regular and very peculiar appearance, especially when examined with a magnifier.

From the solutions of this compound in water, muriate of barytes and nitrate of silver produced copious brown precipitates, as did also protonitrate of mercury and nitrate of lead; but oxymuriate of mercury produced no immediate precipitate, and that obtained from acetate of zinc was of a paler vrown colour.

From these experiments Dr. Prout concludes that the remarkable specimen of urine in question owes its black colour to a compound of a peculiar principle with ammonia, as Dr. Marcet had inferred from his own trials; but he is moreover inclined to think that the black principle itself, such as obtained from the urine by the action of dilute acids, may be considered as a new body possessed of acid properties. From the small quantity of the specimen, however, which could be spared for Dr. Prout's experiments, it was impossible to obtain complete and decisive evidence on the nature of this substance; but it appears to be sufficiently characterized as a peculiar acid, and to bear a closer analogy to the lithic acid, or rather to some of the compounds which it forms when acted upon by the nitric acid, than to any other principle usually found in the urine.

Should this view of the subject be confirmed by farther observations, Dr. Prout would propose to distinguish this new substance, on account of its black colour by the name of Melanic acid. III. Details of a remarkable Phenomenon, which occurred in the Commune

of Juvinas, June 15, 1821. The following extract from the Register of the Civil Department of Juvinas appears worthy of notice, not merely from the fact which is there recorded, though it is curious, but from the nature of the recital. It is astonishing, that in the 19th century the narration of a well-known meteorological phenomenon should be accompanied by the relation of circumstances which recall the ignorance of past ages; that five hundred devils should be named as the presumed agents of the fall of an aerolite; and that to discover this stone, it was judged more proper to carry holy water than mattocks and levers.

That a proces-verbal, in which all these absurdities are recorded, should be signed by magistrates, filling important offices, is still more surprising

The frequent fall of aerolites, during the last fifty years, has fixed the attention of naturalists to the subject. It is generally in calm weather, observes M. Leman, under a cloudless sky, that these phenomena are observed: a ball of fire is perceived, which traverses a certain space, variable in its direction, and which soon bursts with a

noise resembling fire-works, or a battery of cannon at a distance. When it is extinguished, a small white cloud is seen in the same spot, which is quickly dissipated, and it falls upon the ground, sometimes, in large fragments, but more frequently in small quantities, and even single stones. In falling, the stone pierces the. ground for a considerable distance, according to its size and hardness. At the time of its fall, it is hot, and gives out a sulphurous smell ; it is covered entirely with a black crust, without it has struck, in its fall, against a rock or very hard substance; then it flies into a thousand pieces, and shows no crust.

With these preliminary observations, persons the least instructed in meteorological phenomena, will be able to form an exact idea of the facts contained in the following account, of which the copy is duly certified

We, Mayor of the Commune of Juvinas, Canton d'Antraigues, Arrondissement de Privas, departement de l'Ardêche, report, that on the 15th of this present June, warned by a frightful noise, which was heard in our commune, and those which surround it: about three o'clock in the afternoon, we apprehended that some great and extraordinary event was about to effect a general destruction in nature, which obliged us successively to adopt regulations to satisfy us, that no one in our jurisdiction had been the victim of the phenomenon which at first appeared to be inexplicable.

At length, after some days had elapsed, we were informed that a meteor, of which history furnishes no similar account, had burst upon the mountain de l'Oulétte, in the hamlet of Cros du Libonez, forming a part of our commune; and, according to Delmas, who is seventy years of age,

its appearance was preceded and announced by two strong explosions, occurring nearly together, resembling the discharges of two large cannons, and followed by a frightful noise, that continued for more than twenty minutes, which spread alarm and consternation amongst the inhabitants, who believed they should be immediately swallowed up by some abyss ready to open under their feet: the flocks fled, and the goats and sheep collected in groupes. At the same time a black mass was seen coming from behind the mountain de l'Oulétte, describing, as it descended in the air, a quarter of a circle, and sinking into the hollow of the valley of Libonez.

This remarkable circumstance was scarcely perceived by any but children, who, less alarmed than more competent persons would have been, followed the direction, and have since pointed out the exact spot where this mass was swallowed up. Delmas adds that he heard in the air a confusion of voices, which he thought were, at least, five hundred devils, and whom he considers as the agents that transported this alarming phenomenon: at the moment he said to Claude Vaisse, one of his neighbours (who, like himself, was in the fields) “Do you hear; do you understand the language of all these people ?" This person replied frankly,—" I do not comprehend them;" but they were both persuaded that this mass was carried by infernal spirits. Delmas, for the latter reason, said to Vaisse, have

only tinie for one act of contrition,” cast his eyes on the ground, bowed his head, and tranquilly waited for death. Such was the consternation of all the witnesses of this terrible event that, according to their con

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