and at the same time the pure barytes be found not to contain them, the question at issue would be decided: if otherwise an account of the experiments should be published, which would show that the metallic lustre was derived from no foreign or adventitious ingredient." Thus far Dr. Paris; from all which it appears, that the presence of a metal is admitted; the only doubt consists in the nature of this metallic body. I am therefore to consider the question as at rest respecting the metallic lustre; and am only called upon to decide, to what metal this lustre ought to be attributed.

I might discuss this question at once, by saying that if this were really a metal, held in solution by hydrogen gas, and deposited during its combustion "as a metallic film upon the substance held in contact with the burning stream of gas," how comes it to pass, that it is not similarly deposited during the fusion of other refractory bodies, such as rock crystal, corundum, zircon, cyanite, &c.? Would not a similar deposition always take place under similar circumstances? The experiments, however, which have been proposed by Dr. Paris, have been all duly performed; and the following account of them will show, that the metal which he confesses having seen in barytes, is owing to "no foreign or adventitious ingredient."

Monday, July 7.-Having reduced pure barytes to the metallic state, a portion of the substance exhibiting metallic lustre, was exposed to the action of distilled water, containing a few drops of pure nitric acid. Its solution was accompanied with effervescence. Tincture of galls was then added; but there was not the slightest alteration of colour to denote the presence of iron, nor any precipitation of this metal. Afterwards the same experiment was repeated, adding only sulphureted hydrogen as a test for zinc, instead of the tincture of galls, but without effect. Prussiate of potash was also added, but there was no precipitation of zinc. A green colour appeared; from which appearance, iron might be supposed present; but it was observed that the same hue was manifested to prussiate of potash when pure barytes was dissolved in distilled water. These experiments were renewed in the presence of several persons, but always with the same negative results. Upon the addition of sulphuric acid a precipitation took place of the sulphate of barytes. Hence it is proved that the metallic lustre exhibited by the barytes cannot be owing either to iron or to zinc used in the preparation of the hydrogen gas necessary for effecting its fusion; because the most minute portions of these metals would have been detected by the re-agents here mentioned.

Having thus replied, and I hope satisfactorily, to the observations made by Dr. Paris, I will now conclude this letter by noticing a few other experiments which may contribute to the amusement of your readers :

EXPER. I. Corundum.-If during the fusion of this substance it be allowed to fall, while hot, upon a deal board, it will become

coated over with a film of carbon, exhibiting the highest pseudometallic lustre, which however disappears upon the action of the file. The same happens in the fusion of rock crystal, of pure alumine, magnesia, and many other refractory bodies. The appearance of this pseudo-metallic lustre might deceive any person; but it is distinguished from reguline lustre in this circumstance, that the file removes it.

EXPER. II. Crystallized Phosphate of Lime, found near Bovey, in Devonshire.-No decrepitation. Phosphorescence. Fuses into a black shining slag; depositing on iron forceps a cupreous-coloured powder. Scintillation-reddish coloured flame. Upon filing the slag we observed a globule of white metal, resembling silver, which does not alter by exposure to air.

EXPER. III. Crystals deposited during the Fusion of Wood Tin. -In many recent experiments for the reduction of wood tin to the metallic state, when fused, per se, before the ignited gas, we have observed a deposit of white shining vitreous crystals in quadrangular tables, the nature of which has not been ascertained. These crystals are formed upon the white oxide which results from the combustion of the metal.

EXPER. IV.-Hydrogen gas prepared by the action of zinc on water with muriatic acid, when condensed alone in the reservoir of the gas blow-pipe, and ignited, was found to have heat enough for the fusion of platinum foil, and for the combustion of iron wire.

EXPER. V. Protoxide of Chromium.-Mixed with oil it was easily fused, and white fumes were disengaged, but the metal did not appear to be revived by this process.

EXPER. VI. Metalloidal Oxide of Manganese.-Admitted of easy fusion. Afterwards the file disclosed a metal white as silver, on which the teeth of the instrument were visible. This metal proved to be a conductor of electricity.

EXPER. VII. Alloy of Platinum and Gold.-When fused in equal parts by bulk, a bead was obtained so highly malleable that it was extended by a hammer without separation at the edges. Colour nearly the same as gold. When two parts of platinum* were fused with one of gold, the alloy proved brittle.

Cambridge, July 19, 1817.

I remain, Sir, yours, &c.

EDWARD DANIEL CLARKE.

* In all experiments where platinum is fused before the ignited gas, a vivid scintillation may be observed, like that exhibited by iron wire during its combustion: but it has not yet been ascertained whether this scintillation be owing to the dispersion of minute globules of the platinum in a state of ebullition; or to the combustion of the metal; or of any impurities it may contain. It takes place after repeated fusion.

ARTICLE XII.

Proceedings of Philosophical Societies.

ROYAL SOCIETY.

On Thursday, June 26, the following papers were read :Some Account of the Nests of the Java Swallow, and of the Glands that secrete the Mucus of which they are composed. By Sir Everard Home, Bart.

Observations on the Hirudo Complanata and the Hirudo Stagnalis, now formed into a distinct Genus, under the name of Glossiphonia, by Dr. J. R. Johnson. Communicated by Sir Everard Home, Bart.

Account of the Cure of a diseased Foot, arising from an Injury to the Coffin Bone. By Wm. Sewell, Esq. Communicated by the President.

On the Parallax of the fixed Stars. By John Pond, Esq. Astronomer Royal. Mr. Pond found that when his observations were made with the precautions indicated in a former paper, there was no evidence whatever of any parallax in the stars examined.

Observations on the Gastric Glands of the Human Stomach, and the Contraction which takes place in that Viscus. By Sir Everard Home, Bart.

The Society adjourned during the interval of the long vacation.

GEOLOGICAL SOCIETY.

May 16, 1817.-A paper by Dr. Berger, entitled, Note on the Specific Gravity and Temperature of Sea Water in different Places, was read.

The temperature and degree of softness of sea water are considered by the author as circumstances of considerable importance to geologists, and he has communicated to the Society, in the form of a table, such observations as he has been able to make.

The mean of five experiments on the water of the Irish Sea and the North Sea gives a specific gravity of 1.01875, which is less than the results given in Kirwan's table.

The mean temperature, according to the observations which were taken at various times, both of the day and of the year, is

Of the sea water of the surface...

Of the atmosphere in the shade

Ditto in the sun

....

57.07 Fahr. 55.87

62.90

In passing over from Dublin to Holyhead, on Dec. 27, 1812, the

observations made were as follows:

Air in shade.

At before ten, a. m. six miles from Howth 44
14
Noon, seven leagues from Howth

Two o'clock, p. m. 12 or 14 leagues from
Howth

Four o'clock, six or seven leagues from
Holyhead

50

...

Sea at surface.

......

45...... 50+

45..... 531

The author considers that these circumstances confirm an idea formerly entertained, that the agitation of the sea by a storm increases its temperature.

Dr. Berger has also given a table of the temperature at the surface of several lakes in the North of Ireland, of which the mean is, that of the air in the shade being 58.352, that of the water at the surface was 59.224. These results accord with those of Dr. Irving's observations made in the North Sea, and of Dr. Wollaston's on the River Thames, in showing the temperature of the water at the surface to be above that of the atmosphere; but in Dr. Wollaston's experiments the difference is more considerable.

June 6.-Mr. Bigge's paper was read, entitled, Observations on the Cheviot Hills and the North-Western Boundary of Northumberland.

The chain of hills extending from Thirlemoor, near the head of the Coquet, to the plain on the south side of the Tweed, is composed chiefly of porphyry and syenite of various modifications. In several parts large craggy rocks, having the appearance of cairns, arise above the surface. These are composed principally of whinstone or petrosiliceous porphyry with hornblende; but Mr. Bigge has not in any instance been able to observe their junction with the main rock.

The Coquet and the Bremish rivers rise in these hills, and the author traces their courses as a guide to future inquirers. The course of the Coquet is at the extreme point of the porphyritic range to the south. It passes over a considerable extent of slate, rising to the NNE, though nearly vertical, and curved in some places.

Further on its bed is porphyry, interrupted in some instances by whinstone dykes. At Limshiels the porphyry is succeeded by a shistose lime-stone dipping SSW, and alternating with a coarse sand-stone, and the river continues its course to the sea through various beds of lime-stone and sand-stone, but which meet with an interruption from a whin dyke at Brainsaugh, below Felton.

The Bremish rises on the south side of Cheviot, and passes for several miles between high hills of porphyry. On the summit of one of them, Shilmoor, the author observed a vein of quartz traversing the hill from SE to NW. At Branton the river quits the porphyry, and passes along a plain of sand with hillocks of gravel. * Wind NW. + The wind having greatly increased. Wind still higher.

Turning to the north, it soon afterwards takes the name of the Till, and passes into the Tweed through beds of sand-stone, having on the east beds of lime-stone and coal. At Roddam Dean a bed of sand-stone occurs covered with a coarse breccia.

Blocks of granite, of a grey colour and fine grain, are found in the hillocks on the plain of Bewick.

June 20. Concluding Meeting.-The following communications were received since the last meeting:

Observations on certain Sand-stones. By A. Aikin, Esq.

Notice on the Physical Constitution of the Passage of Mount St. Gothard. By Dr. Berger.

Account of the Place where some Specimens presented to the Society by Mr. Swedenstierna were found. By S. Solly, Esq.

Sweden does not present that appearance of regular stratification which is observable in this country. Its face is covered with crags and fragments; but some of the larger basins into which its surface is indented contain insulated series of horizontal strata. Many ridges of granite gravel running from north to south cover its surface. In one of these ridges near Finbo a quarry was opened by M. Gahn, jun. and in the subjacent rock the pyrophysalite was first discovered, and subsequently various other new and rare minerals. The rock in which these substances are found has the character of a large grained granite.

ROYAL ACADEMY OF SCIENCES.

Analysis of the Labours of the Royal Academy of Sciences of the Institute of France during the Year 1816.

PHYSICAL PART.-By M. le Chevalier Cuvier, Perpetual Secretary. (Continued from vol. ix. p. 479.)

MINERALOGY AND GEOLOGY.

Greenland furnished some years ago a mineral in small dodeca hedral crystals of a celadon-green colour, to which the name of sodalite has been given, because it contains nearly the fourth of its weight of soda united to silica and alumina.

M. Count Dunin-Barkowskig, a Gallician gentleman, and a zealous and well-informed mineralogist, has discovered a colourless variety of this stone in large prisms in that part of Vesuvius called Fosso Grande, so celebrated for the number and variety of minerals which it has given to collectors. The composition of this mineral, very similar to that of glass, might have appeared striking among crystals thrown out of a volcano, if it were not accompanied by a number of other species which have nothing in common with glass, and if the sodalites of Greenland did not occur in a place which exhibits no traces of subterraneous fires.

Geology, in the scientific form to which it has been lately eles