poured into ammonia a white powder falls, which detonates feebly, and affords iodine and a gas not capable of supporting combustion. When the acid is coloured the precipitate formed is black, and detonates much more loudly.

Tin and iodine, when combined, form a body possessing acid properties, though no hydrionic acid could be detected in it. 4. On the action. of some compound gases on iodine. It absorbs sulphureted hydrogen and forms a reddish brown fluid. When iodine was sublimed in olefiant gas a little reddish brown fluid was formed. It produced no change on nitrous gas nor carbonic oxide; but when mixed with carbonic oxide in the gaseous state and exposed to the light of the sun, a combination seems to take place. 5. On the mode of detecting iodine in combinations, and on certain properties of its compound with sodium. The marine productions of the Mediterranean contain less of it than the sel de varec. Ashes of the ulva, that abounds on the coast of Languedoc, yielded traces of it. As did the ashes of the following plants: fucus cartilagineus, fucus membranaceus, fucus rubens, fucus filamentosus, ulva pavonia, ulva linza.

The ashes of corralines and sponges exhibited no traces of it. Its presence is detected by its property of tarnishing silver, and by the red fluid which alkaline leys containing it form with sulphuric acid.

Sir H. Davy conceives it possible that the superiority of bay salt in curing fish and meat, may depend upon the presence of this substance. He rubbed pieces of beef with iode and oxiode of sodium. They did not putrify. The piece rubbed with the iode became brown, soft, and tender; that rubbed with the oxiode hardened considerably and became paler.

XI. Observations respecting the natural Productions of Saltpetre on the Walls of subterraneous and other Buildings. By John Kidd, M.D. Professor of Chemistry in Oxford.-The formation of nitre upon calcareous stones in certain situations has been long known, and advantage has been taken of it to procure that important salt in great quantities; though no satisfactory theory of the formation of the salt itself has yet been offered to the public. The present paper contains a set of observations on the appearance of an efflorescence of saltpetre on the walls of the Ashmole laboratory at Oxford, a large ground room, sunk below the area of the street. The walls are built of Oxford lime-stone, a granular floetz limestone containing many fragments of shells, of vegetable bodies, and composed of 96 carbonate of lime, and 4 of ochrey sand. The salt formed was nearly pure, though it contained traces of lime and of sulphuric and muriatic acids. What was formed in winter contained most lime. The formation of this salt was most rapid in frosty weather; it formed slowly, and the quantity even diminished in moist weather after it had been deposited. Exclusion from the air did not preclude the deposition of the salt, though it diminished it considerably.

XII. On the Nature of the Salts called Triple Prussiates, and on Acids formed by the Union of certain Bodies with the Elements of the Prussic Acid. By Robert Porrett, jun. Esq.-I have already given a pretty full account of this important paper in the number of the Annals of Philosophy for January, 1815, to which I refer the readers. I intend to publish an abridgment of the paper in a future number of the Annals, as it contains some discoveries which I consider as important.

XIII. Some Experiments on the Combustion of the Diamond, and other Carbonaceous Substances. By Sir H. Davy.-Diamonds were put in a small glass globe filled with oxygen gas, and kindled by means of a burning-glass. When once set on fire, they were found to burn, though removed out of the focus of the lens. The result of the experiments was, that diamonds, when burnt, produced only carbonic acid gas, and no alteration took place in the bulk of the gas in which the combustion was performed. Hence it follows that the diamond consists of pure carbon. Plumbago and charcoal, besides carbonic acid, formed also a sensible portion of water when burnt, and the bulk of the oxygen gas was diminished. Hence these bodies contain hydrogen as a constituent, though only in a very minute proportion.

XIV. Some Account of the Fossil Remains of an Animal more nearly allied to Fishes than to any other Class of Animals. By Sir Everard Home, Bart. F.R.S.-These bones were found in a cliff on the sea coast of Dorsetshire. The skull was pretty perfect; most of the other bones were broken and crushed. The ribs were 60, and make the skeleton 17 feet long. These bones approach most nearly to those of fishes, though the author considers the animal as not having been a perfect fish, but as constituting one of those intermediate links so commonly observed in the animals of New South Wales.

XV. On an easier Mode of procuring Potassium than that which is now adopted. By Smithson Tennant, Esq. F. R.S. This method is to put the potash and iron turnings together into a gunbarrel about a foot and a half long, and covered with a lute composed of Stourbridge clay, partly in its natural state, and partly previously baked. Into the mouth of the gun-barrel another iron tube about eight inches long is to be put, perforated at the lower extremity, and having its upper end projecting about an inch beyond the gun-barrel. The mouth of the gun-barrel is shut by another tube which slips over it. The mouth of it is filled by a perforated cork, through which there passes a bent glass tube, having in it a drop of mercury. This apparatus being exposed to a strong heat for an hour in a smith's forge, the potassium is found perfectly pure in the upper perforated iron tube.

XVI. On the Influence of the Nerves upon the Action of the Arteries. By Sir Everard Home, Bart. F.R.S.-Our author accidentally observed that the application of stimulants to nerves produced a violent increase of the action of the blood-vessels connected

rock is for the most part a compact, sonorous, dark blue trap, nearly with them. He laid bare the carotid artery of a dog, and upon touching the intercostal nerve and par vagum with potash, a violent increase in the action of the artery took place. The same experiment succeeded equally in rabbits; so that the circulation of the blood is not wholly dependant upon the heart and the elasticity of the arteries, the action of the nerves is necessary to regulate the distribution of it to the different parts of the body.

XVII. On the Means of producing a double Distillation by the same Heat. By Smithson Tennant, Esq. F.R.S.-The method is to make the worm from the first still pass through a second, which is air-tight, and has attached to it a worm connecting it with an airtight receiver. Heat is applied to the second still till the liquid in it is made to boil; the cocks are then shut, and the distillation carried on by the heat communicated by the worm from the first still.

XVIII. An Account of some Experiments on Animal Heat. By John Davy, M.D. F.R.S.-From these experiments it appears that there is no material difference between the specific heats of veinous and arterial blood, except what arises from difference in the specific gravity; that of the former being 1·049, and of the latter Our author considers the relative specific heats as 0.913 and 0.903. The temperature of arterial blood is higher than that of venous, and the temperature of the left side of the heart than of the right. The temperature of parts diminishes as the distance of the parts from the heart. These results are incompatible with Dr. Crawford's theory of animal heat, but agree with the theory of Dr. Black.

ARTICLE X.

Proceedings of Philosophical Societies.

GEOLOGICAL SOCIETY.

May 19-A notice accompanying an additional drawing to the paper on Vegetable Remains in Chalcedony, by Dr. Macculloch, was read, describing a vegetable remain possessing decidedly the genuine characters of conferva.

June 2.-The Secretary reported that a communication on the Native Tellurium of Norway had been received from Professor Esmark, of Christiana.

Dr. Macculloch's paper on the Isle of Sky, begun at a former meeting, was concluded.

The principal group of mountains in Sky is the Cuchullin. This elevation probably exceeds 3000 feet, and the principal escarpments look east and north. It is remarkable for the spiry granitic form of its summits, and its naked barrenness, owing to the strong resistance which it opposes to the usual causes of decomposition. The

allied to green-stone, passing sometimes into syenite, sometimes containing glassy felspar and hyperstene, and sometimes composed merely of quartz and hornblende. It is traversed throughout by dykes of basalt, in some places approaching to pitch-stone, and appears to rest on a very compact grey quartzy sand-stone, which does not contain shells, and like the superincumbent trap, is tra versed by veins and dykes of basalt.

Adjacent to the Cuchullin is another group, called the Red Mountains, of lower elevation than the former, presenting rounded outlines, and so covered with fragments in a state of decomposition, that the massive rock can rarely be perceived. The chief constituent ingredient of these mountains is flesh-red felspar, passing into claystone, and containing a small and variable proportion of hornblende and quartz. This rock, like that of the Cuchullin, is also traversed by veins of trap, and probably by veins of granite.

The northern portion of the island consists for the most part of floetz trap in beds approaching to horizontal, alternating with sand-stone, and presenting seams of basaltic coal generally broken, imperfect, and of little extent. This trap offers the usual varieties, namely, basalt, either perfect, or approaching to wacke, green-stone, and amygdaloid. This latter variety contains nodules of steatite, balls of filamentous mesotype, crystallized mesotype, chabasite, and occasionally stilbite and ichthyophthalmite. In some parts the shale and sand-stone adjoining the trap are indurated, and more or less altered, the former in particular being converted into lydian-stone and botryoidal schist. The whole of the eastern shore of Strathaird exhibits one continuous cliff of blue compact lime-stone, split by numerous fissures, and hollowed out into caves.

At Kilbride, near Loch Clapin, another lime-stone district occurs, the connections of which it is very difficult to ascertain. This limestone is unstratified, contains no organic remains, is of a granular structure, and is in many places a perfect marble, more or less coarse in its grain, of a white, blue, and yellowish-green colour (this latter from an intermixture of serpentine), and applicable to various uses in ornamental architecture. This lime-stone ceases a mile or two short of Bradford; and on the shores of this latter water another formation of lime-stone, totally distinct from the other, makes its appearance. This forms thin beds, alternating with sand-stone and shale, is highly bituminous, and contains annoniæ, ammonitæ, and other shells, and is traversed by trap veins.

Between Loch Oransa and the northern part of the shore near Bradford is a tract of quartz rock, which also occurs in other parts of the district of Clate, accompanied by various primary schistose rocks, and intersected by veins of trap.

A paper by J. Williams, jun. Esq. of Scorvier, describing the mine of Huel Peever, was read.

The tin vein of Huel Peever, in the parish of Redruth, in consequence of its intersection by cross veins, by the underlie of a

parallel copper vein, and by the oblique course of a channel of porphyry, was lost, and exercised the skill of the ablest Cornish miners for more than 40 years before it was recovered. A description of the particular deviations produced in the course of the vein by each of these disturbing causes is given in this paper, and its accompanying plans and sections.

WERNERIAN SOCIETY.

At the meeting on 21st January, Mr. P. Syme laid before the Society an account of some remarkable atmospheric appearances observed by him during a thunder-storm on the 29th of July 1814, accompanied with several beautiful drawings executed by him from sketches which he took at the moment.

At the meeting on 4th February was read an essay on the germination and physical economy of ferns, by Dr. Yule.-At the same meeting there was read an account of the mineralogy of the Red Head, by Dr. Fleming. The Red Head is a well known promontory in the county of Forfar. The rocks consist of sand-stone and gravel-stone. The author seemed inclined to consider these rocks as mechanical deposits, as they bear the closest resemblance in all respects, except in being cemented, to beds of sand and gravel in the neighbourhood. The sand-stone belongs to the old red sandstone formation, in which many trap-rocks rising into hills, such as the Ochils, and hills of Kinnoul and Perth, occur in the form of great beds.

At the meeting on 25th February, Professor Jameson read a short account of the places where fossil remains of elephants have been found, and exhibited the tooth of a mammoth discovered by William Auld, Esq. in Hudson's Bay, this being the first time that such remains have been observed so far to the northward in America. Professor Jameson also read a notice concerning the indurated talc which occurs in quantity in the island of Unet, one of the Zetlands, and which, he stated, might be profitably brought to market, the article being in demand for removing stains from silks, &c. and selling at a considerable price.

At the meeting on the 11th of March, Professor Jameson read the continuation of his mineralogy of the Lothians.

At the meeting on 25th March was read a description of a new species of water ouzel or dipper, found in this country by James Wilson, Esq. A specimen of the young bird and a drawing of the bird in full plumage were exhibited. It differs from the common ouzel chiefly in the deep rufous band on the lower breast being wanting, and in the breast feathers being marked with transverse waved lines, from which last circumstance Mr. Wilson proposes to call it Aquatilis undulatus.

At different meetings of the Wernerian Society in January, February and March, a paper by Mr. Scoresby junior of Whitby, on Polar Ice, and the Practicability of a Journey to the Pole, excited much interest.