patic air, and the manner of obtaining it; the general characters of this air; the action of the hepatic and other aereal fluids. upon one another; the action of hepatic air, and of acid, alcaJine, and inflammable liquids upon each other; the properties of water faturated with this air; and the properties of alcaline Jiquors impregnated with it. Whoever peruses these experiments with moderate attention, cannot fail to agree with, or rather to anticipate the Author, in his conclufion from them, reSpecting the conftitution of hepatic air,-that it is no other than actual fulphur, kept in an aereal ftate by union with the matter of heat.

Such a multiplicity of diftinct facts, defcribed with as much brevity as is confiftent with the neceffary precifion, can admit of no abridgment. We fhall juft mention a few of them, to give our Readers fome idea of the grounds on which the abovementioned conclufion is built.

The most delicate teft of hepatic air, is a folution of filver in nitrous acid, which becomes black, brown, or reddish brown, from contact with this air, however mixed with any other air or fubftance. The precipitate is found to be fulphurated filver; and the fame general effect happens in other metallic folutions, though with fome differences in particular phenomena.

When this air is mixed with common, phlogifticated, dephlogifticated, inflammable, or marine-acid airs, no diminution of bulk is obferved, nor do the fluids appear to have any action on one another. But with vitriolic or nitrous air, the cafe is different; on mixing the hepatic air with either of thefe, a great diminution happens, and the containing jar becomes lined with fulphur.

During the combuftion of the hepatic air, a little fulphur is conftantly depofited.

Though foluble in water, it does not remain permanently diffolved; it renders the water turbid on ftanding for a few days, and at length is depofited in the form of fulphur. Spirit of wine abforbs more of it than water, about three times its own bulk; the liquor, in colour brown, is a true folution of fulphur; and this is the eafieft method known of combining fulphur with vinous fpirits.

One of the readieft methods of obtaining the hepatic air is, by precipitating a folution of hepar fulphuris, that is, fulphurated alcali, with marine acid. Acids contain the matter of beat, in a latent or combined ftate; and in uniting with earths or alcalies, they emit that principle, which then acts as fenfible heat. Now, in the union of the acid with the fulphurated alcali, the fenfible heat produced is much less than in its union with the alcali alone; and the quantity of heat by which the one falls fhort of the other, muft be prefumed to enter into the compofition of the hepatic air that is formed at the fame time.

And

And conversely, when the acid is previously combined with a foluble earth, though it ftill decompofes the hepar, no hepatic air is produced, for want of the matter of heat, which had before been expelled from it by the earth. The first of these curious facts is from Mr. Scheele, the other is Mr. Kirwan's.

The Paper concludes with fome experiments on phosphoric hepatic air; from which it appears, that this air is nothing else but phofphorus itself in an aereal ftate; differing from fulphur in this, among other points, that it requires much less latent heat to throw it into an aereal form, and hence may be disengaged from fixed alcalies without the affiftance of an acid.' Obfervations on the Sulphur Wells at Harrowgate, made in July and August, 1785. By the Right Reverend Richard Lord Bishop of Landaff, F. R. S.

His Lordship gives an account of the late difcovery of fome new fprings in this neighbourhood, fimilar to the old; of the nature and ftrata of the adjacent ground; of the temperature of the waters, which is found to differ in the different wells at the fame time, and in the fame well at different times, following the variations of the external heat or cold; whence it fhould feem that the springs do not lie deep, or that the water runs for a confiderable diftance in a channel fo near the furface of the earth, as to be affected by the temperature of the atmofphere. Their only mineral impregnation, befides the fulphur, is common falt, and of this alfo the quantity is very different even in the four wells at the village, though fo near to one another, that they might all be inclofed in a circle of feven or eight yards in diameter: the ftrongeft appears to contain one ounce of the falt in about four pints and a half, and the weakeft not quite one third fo much.

That these waters are impregnated with actual fulphur, his Lordship has established beyond a poffibility of doubt; for it appears from his obfervations, that fulphur is found sticking to the bafon into which the water fprings,-fublimed upon the ftones which compofe the edifice furrounding the well,-adhering to the fides of the tubs in which the water ftands,-subfiding to the bottom of the channel in which the water runs, -and covering the furface of the earth, and the blades of grafs over which it flows.

With regard to the nature or medium of the impregnation, bis Lordship fufpected it to be an aereal fluid, before he became acquainted with Bergman's obfervations on that fubject, to whom he readily gives up both the priority of the discovery, and the merit of profecuting it. He obferves, that the air feparable from Derbyshire lead ore, and from black-jack, by folution in vitriolic acid, impregnates common water with the fulphureous fmell of Harrowgate water; that fea wreck, cal

O 2

cined

cined to a certain point, does the fame ;-that on breaking into an old coal-work, in which fome wood had long been left rotting, a great quantity of water iffued out, fmelling like the Harrowgate, and leaving, as that water does, a white fcum on the earth which it paffed over ;-that on opening a well of common water, in which a log of rotten wood was found, a strong and distinct smell of Harrowgate water was perceived;-and that fulphureous waters found in fome bogs or moraffes feem to arife from rotten wood;-that fhale, of which there is a ftratum extended all over the country about Harrowgate, and from which the fulphur wells fpring out, contains both vitriolic acid and phlogifton, which are the conftituent parts of fulphur; and that fome pieces of the fhale, when calcined to a certain degree, have been found to communicate the fulphureous impregnation to

water,

Additional Obfervations on making a Thermometer for measuring the higher Degrees of Heat. By Mr. Jofiah Wedgwood, F. R.S. Of the Author's firft Paper concerning this excellent thermometer, we gave a pretty full account in a former volume *. In that Paper he communicated every thing that experience had then taught him, refpecting both the conftruction and use of this thermometer; but more extenfive practice has fince convinced him, that other managements and precautions are neceffary, in order to bring it to the perfection it is capable of receiving; for pieces made of the fame clay, and exactly of the fame dimenfions, have been found to differ in the degree of their diminution by fire, in confequence of fome circumftances in the mode of their formation, at that time unheeded, and very difficult to be developed.

Thefe circumftances are here inveftigated and afcertained in a manner which does equal honour to the fagacity of the philofopher, and the ingenuity of the artift; and we regret that we cannot give our Readers a fatisfactory account of them, in any compass that can be allowed in our work for a fingle article in fuch a volume. The Paper itfelf is manifeftly a condenfed abstract (if we may be allowed the expreflion) of the refults of experiments, which muft have been amazingly numerous and embarraffing.

When a method had at length been ascertained, of forming any given quantity of clay into pieces that fhall correspond with fufficient accuracy, a more formidable difficulty presented itself, refpecting the quality of the clay; for, contrary to all expectation, clays taken even from contiguous fpots in the fame ftratum, though alike in all other fenfible properties, were found to differ from one another in their degree of diminution; and

* See Rev. vol. lxix. p. 386.

none

none could now be procured that diminished fo much as the parcel originally made ufe of. After various researches and experiments, dictated by a thorough knowledge of the fubject, and which have discovered many curious particulars refpecting the properties of this clafs of earths, he has recourse to an admixture of the earth of alum, the ingredient on which the diminution by fire and all the argillaceous properties depend; and by a due proportion of which the common porcelain clays of Cornwall are made to correfpond in all degrees of heat with the original clay, receiving from it at the fame time fome other important advantages. Coincidence with the original,' he obferves, was not indeed effential; but as many degrees of heat were already before the public, meafured by thermometer-pieces made of the first clay, and as the correfpondence of the firft with Fahrenheit's fcale, had likewife been in fome measure afcertained *, it was defirable that the fame degrees of heat fhould continue to be expreffed by the fame numbers.'

Of the embarraffing properties of fome of the natural clays, we shall mention one, on account of what appears to us a very important confequence refulting from it. Though they continued diminishing with tolerable regularity, up to a certain period of heat, about that in which caft iron melts, yet many of the pieces, urged with a heat known to be greater than that, were found not to be diminished fo much as those which had fuffered only that lower heat. Further experiments fhewed, that after diminishing to a certain point, they begin, upon an increase of the heat beyond that point, to fwell again and as this effect is conftant in certain clays, and begins earliest in those which are most vitrifcible, and as clays are found to fwell upon the approach of vitrification, I look upon this enlargement of bulk, however inconfiderable, as a fure indication of the clay having gone beyond the true porcelain ftate, and of a difpofition taking place towards vitrification.-The degree of heat, therefore, at which this enlargement begins, may be confidered as a criterion of the degree of vitrifcibility of the compofition; which points out a new use of this thermometer, enabling us to afcertain the degree of vitrifcibility of bodies that cannot actually be vitrified by any fires which our furnaces are capable of producing.'

Obfervations on the Affinities of Subftances in Spirit of Wine. By John Elliot, M. D.

This Paper, in the form of a letter to Mr. Kirwan, contains fome experiments in confirmation of a pofition which the Author had advanced in a former publication, that certain decompofitions will take place in fpirit of wine, which will not at

* See Rev. vol. lxxii. p. 250.

all in water, nor in the dry way.' The particular decompofition here treated of, is that of diachylum plafter (a compound of litharge and oil) with fea-falt, by boiling them in spirit of wine the acid of the fea falt unites with the litharge, and its alcali with the oil, the two latter forming together a true foap, which diffolves in the fpirit, and may be obtained in its proper form by evaporation. As no feparation takes place in water, it follows, that the apparent affinities depend, not folely upon the attractions of the ingredients to one another, but in part upon their attractions to the liquid employed as an intermedium. In fpirit of turpentine, the affinities were ftill further diverfified; the diachylum diffolved, and the common falt remained at the bottom.

New Experiments upon Heat. By Colonel Sir Benjamin Thompfon, Knt. F. R. S.

From the ftriking analogy between the electric fluid and heat, in refpect to their conductors and non-conductors (bodies which are good conductors of the one being generally fo of the other alfo), it was natural to imagine that the Torricellian vacuum, which affords fo ready a paffage to the electric fluid *, would do the fame to heat. But a feries of curious, and admirably wellcontrived experiments, detailed in this Paper, prove, without leaving a fhadow of doubt, that the vacuum conducts heat far more fluggishly than air;-that, nevertheless, air of different denfities differs little in this refpect;-but that the conducting power of air is very greatly increafed by humidity. On this remarkable effect of moisture in the air, the Author remarks, with what infinite wifdom and good nefs Providence appears to have guarded us against the ill-confequences of exceffive heat and cold in the atmosphere: for were it poffible for the air to be as damp during the fevere colds of the winter months, as it fometimes is in fummer, its power of conducting the heat from our bodies, and of courfe its apparent coldness to us, would be intolerable; but happily its power of holding water in folution, and therewith its power of robbing us of our animal heat, diminishes in proportion as its coldness is increased. If colds or catarrhs are occafioned by our bodies being robbed of heat, the reafon is plain why thofe diforders prevail moft during the cold autumnal rains, and on the breaking up of the froft in fpring. It is hence alfo plain, why damp houfes, and damp beds, are

Though it has lately been difcovered, that the perfect vacuum does not conduct electricity, this does not affect the Author's comparifons; for the vacuum, in his experiments, was fuch as may be prefumed to have been a conductor; and in either cafe, the difference, in that refpect, between the electric fluid and heat is equally ftriking.

fo