eighteen inches diameter, he could charge a single jar of 160 inches of coated glafs fo highly as to make an inch of the fmalleft iron wire vanifh into fmoke, and three inches exhibit the phenomenon of filaments floating in the fmoke into which the wire was converted; which was mentioned in the description of Dr. Van Marum's great machine with nine, and, once, with only fix revolutions of the plates, he melted eight inches of wire: but this appears to be the greatest effect of fuch a jar, whatever be the fize of the machine with which it is charged. It is fomething remarkable that two, and even three, fuch jars required not more revolutions of the machine to pro. duce this effect, than a single jar; and that a jar, containing 5 fquare feet of coated glafs, demanded only one revolution more than a common fized one. It is alfo obfervable that jars will bear a much greater charge in fummer than in winter: the fame jar which, in fummer, could be charged fo high as to melt eight inches of wire, would not, in winter, melt more than five, and would break if the charge were increafed beyond this height. The standard jar will, in fummer, discharge itfelf, when the balls of the elerometer are half, or even three quarters, of an inch diftant from each other, before any flashing is perceived on the uncoated glafs: but, in winter, this flafhing is feen before it difcharges at half an inch. Batteries like wife may be charged much higher in fummer than in winter, and with much less danger of breaking the jars. Farther experiments are neceffary in order to account for this phenomenon in a fatisfactory manner: but, in the mean time, thofe of Mr. CUTHBERTSON have led to the difcovery that much greater effects may be produced by a fmall battery, if not wiped perfectly dry, than were formerly thought poffible. The fixing of a metallic ftain on paper, by tranfmitting the charge through pieces of wire laid over it, which was effected by Dr. Van Marum's grand machine with a battery of two hundred and twenty-five fquare feet of coated glafs, our author has effected with a furface of fixty fquare feet, charged by a machine of two plates of thirty-three inches. We have fince feen this experiment performed on all the metals, except Platina, with a battery of fifteen fquare feet, charged by a machine with a fingle plate, twenty-four inches in diameter, which was made by our author. With the battery, which Mr. CUTHBERTSON here mentions, fix inches of platina wire,

th of an inch in diameter, were melted to globules. On this occafion, he contrived a very ingenious apparatus, in order to confine the wire, through which the explofion was tranfmitted, in any kind of gas; the diminution of which, by af

Rev. vol. lxxiii. p. 556.

terward

terward opening a communication with a glass tube filled with water, and furnished with a fcale, might be accurately obferved.' The tube, which contained the gas, was 1 inch in diameter, and 15 inches long, and each of the divifions on the scale expreffed the volume of a drachm of water. The tube being filled with oxygene gas, the battery was discharged through two feet of iron wire, th of an inch in diameter, which was in part melted to globules, and the remainder reduced to a fine duft; the diminution of the gas amounted to a cubic inch: the experiment was then tried with fourteen inches of the platina wire above mentioned, which was reduced to a light-brown powder: but the gas was not at all diminished. Gold and filver wire were alfo reduced to powder, without the leaft abforption of oxygene. Fourteen inches of leaden wire were, by the explosion, changed into a fine white powder, which was revived by being expofed to the flame of a candle; the gas abforbed was about an ounce measure: the refult was nearly the fame when the experiment was tried in common air, only that the powder was lefs in quantity, inferior in whitenefs, and fo damp that it ran into lumps. With tin, the effect was exactly the fame; except that the powder was ftill whiter and in greater quantity. This experiment was repeated in air, in which a red hot coal had been extinguifhed: but then the wire was melted to globules, and no powder was produced; the diminution of this air was about two drachms.

Mr. CUTHBERTSON's removal to London has prevented him from purfuing thefe interefting experiments any farther:we hope that he will now be able to refume them, and will make the public acquainted with their refult, which may be of great ufe in illuftrating the theory of oxydation.

ART. IX. Correfpondence, c. i.e. The Correfpondence between General DU MOURIER and PACHE Minifter of War, during the Campaign in Flanders and Brabant in 1792. 8vo. pp. 166. Paris. 1793.

TH HESE letters have no other evidence of authenticity than what arifes from their contents, which feem to favour this fuppofition. They are introduced by the editor's dedication to his fellow-citizens, to which no name is fubfcribed: but, from the tenor, it seems to have been written by DUMOURIER; who informs his readers that his motive for publishing this small fpecimen of his correfpondence was to convince them of the many obstacles that he had to encounter, when entrusted with the command of the French army. This is indeed almost the only information that can be collected from thefe epittles,

which abound with complaints of a want of due attention, in the minifters and executive council, to furnish the troops with provifions, clothing, and the neceffaries of war; in confequence of this neglect, the General fays, he was often obliged to delay his operations, because the army was two much diftreffed to act, and he was hence difabled from purfuing advantages which, if well improved, might have totally ruined the enemy. He accufes the miniftry of thwarting his defigns, of removing from their employments thofe in whom he placed the greatest confidence, and of committing the care of fupplying the army to Jews and monopolifts, who had no other object than their own private fortune. Thefe complaints, frequently recurring, weary the reader, but they are expreffed with a temperate firmness; and the General's letters difplay fo much good fenfe and confiftency of character, that we cannot help deeming it a very fortunate circumftance for the allied powers that he was prevented from carrying his plans into immediate execution. In his conduct, while in the Netherlands, he appears to have been directed by a found policy, in wifhing to avoid every thing that might give offence to the inhabitants, and to purfue fuch measures as might conciliate their interefts with thofe of France. He repeatedly advifes the miniftry to purchase of them as much as poffible of the articles required for the use of the army, which, he obferves, would engage the merchants and manufacturers in their favour; he expreffes his difapprobation of the conduct of General La Bourdonnaye, who obliged the magiftrates of Ghent to iffue a proclamation commanding the inhabitants to furnish two hundred thousand facks of corn, a part of which was to be fent into France, and the remainder to fupply the army; and he pofitively refuses to compel the Flemmings to take affignats in payment. His plan with respect to the war appears to have been much more prudent than that which was actually adopted, and he frequently blames Cuftine for pufhing fo far into Germany, without having taken Coblentz and gotten poffeffion of the Rhine.

Such is the chief information contained in these letters, which give us high ideas of DUMOURIER's abilities, both as a General and a ftatefman: whatever may be thought of the merits of the cause in which he was engaged, it appears that, at the period in which this correfpondence took place, he was one of its most powerful fupporters. We are forry that we have no fatisfactory account of his reafons for deferting the republic; and it cannot be afcribed to that venality of which the French accuse him. It was more probably occafioned by his difguft and refentment at the ungrateful manner in which he was treated by the Jacobin faction; and this might make him

wish to leave a fituation in which his plans were defeated and his life threatened by the intrigues of his enemies in the government. Had he totally deferted his principles, and fold himself to the combined powers, we think that he would have met with better treatment from them than he has experienced; for it is not the honesty, but the utility, of men, which recommends them to the notice and favour of politicians.

ART. X. Recherches Phyfico-Chemiques, &c. i.e. Phyfico-Chemical Inquiries Memoir III. 4to. pp. 26. Amfterdam. 1794. N this memoir, Dr. DEIMAN, and his coadjutors Meffrs. TROOSTWYK, BONDT, NIEUWLAND, and LAUWRENBURG, have given an account of fome phenomena which, we believe, have never been obferved before, but which well deserve the attention of chemifts; as they fhew that conclufions, though founded on many experiments, may fometimes be made too general; and that new facts may arife which may render it neceflary to modify even thofe opinions that have been long received, and appear to be most firmly established. Nothing, for instance, was more univerfally believed than that the prefence of oxygene gas, or dephlogisticated air, was abfolutely neceffary to the production of flame; and thefe philofophers were not a little aftonifhed when, on exposing a mixture of copper-filings and fulphur, in a fmall narrow-necked vial, to the heat of a fire of charked turf, they faw that, after the fulphur was melted, the mafs exhaled vapours, fwelled up, and fuddenly flamed with great brightness, very different from that pale light which fulphur generally yields when burning. These phenomena they refolved to investigate, and to inquire how the oxygene gas was produced, to the prefence of which they naturally afcribed them; for they justly concluded that the heat and the vapours of the fulphur muft have expelled the atmofpherical air from the vial. Finding that fulphur alone, when heated in a vial like the former, could not be made to flame, they fufpected that what they had mixed with the copper might have imbibed fome acid, or at least that it contained fome water, from which oxygene gas might be produced. From thefe accidental imperfections they purified it, by fprinkling it with ammoniac, washing it repeatedly with boiling water, and then carefully drying it: but the fulphur, after being thus purified, when mixed with the copper, exhibited the fame phenomena, and flamed as before. In order to be equally certain with regard to the copper, they took, as the pureft they could get, that which the goldfmiths ufe for the alloy of filver; and, in order to be fure that this contained no

oxyd, they heated it in clofe veffels, but could obtain no oxy. gene gas from it; they then let it digeft in ammoniac, to which it gave not the leaft tinge. Hence it appeared that both the ingredients, which they ufed, were free from oxygene; and that their flaming, when mixed, could not be attributed to the generation of gas from this principle.

After feveral trials, in order to afcertain what proportion of copper and fulphur is moft advantageous for the exhibition of this phenomenon, thefe ingenious chemifts found that three parts of the former, and one of the latter, flamed with the greatest brightnefs; and that the experiment was lefs fuccessful, which ever way they varied from this proportion, which appeared to be the most favourable also, when other metals were fubftituted inftead of copper. Iron filings required a greater degree of heat, nor was the flame fo bright as that with which the copper burned; tin and lead required ftill more heat, and zinc the most of all: but thefe metals yielded a very bright flame; especially the laft, which, in this respect, exceeded all the reft. With antimony, bifmuth, mercury, and cobalt, the experiment did not fucceed.

Thefe gentlemen next tried the experiment in vacuo; and, for this purpofe, they inclofed a mixture of 45 grains of copper with 15 of fulphur, in an exhaufted glafs tube, 15 inches in length, and three quarters of an inch in diameter; after the inflammation, they found that the tube contained an inch and a half of gas; of this an inch was abforbed by water, which thence acquired the flavour and fmell of fulphurous acid, and reddened the tincture of turnfole; the remaining half inch appeared, by the fmell, to be fulphurated hydrogene. This gas, they juftly obferve, must be afcribed to a latent refiduum of water, from which it is extremely difficult to purify the fulphur.

The experiment was then performed in gas azote, in hydrogene, and in carbonic acid gas; the mixture flamed exactly as before, nor was the gas, in which the procefs had taken place, found to have undergone any alteration; when oxygene gas was used, the explofion was fo violent as to burft the tube.

A mixture of zinc and fulphur, confined in hydrogene gas, burned with a much redder flame than it had exhibited in the vial; and all the gas in the tube was completely fulphurated: to produce this phenomenon, a very great heat was required; for, as the authors obferved in their first memoir, the combination of fulphur with hydrogene gas cannot be formed, except in a high degree of temperature; and, in this experiment,

• See Review, New Series, vol. viii. p. 53.