1. The fpecific gravity; that of white arfenic is as 3,750, of the earth of molybdæna as 3,460. It 2. Its powdery form, acefcency and folubility in water. has an acid and a metallic tafte, 570 parts of diftilled water, diffolve one in a middle temperature; the folution reddens tincture of turnfole, and precipitates fulpher from a folution of hepar, circumftances which fufficiently evince its acidity. 3. This folution affords a dark red precipitate, when phlogisticated alkali and tincture of galls is added to it. 4. When diftilled with a triple quantity of fulphur, it regenerates molybdena, which gives out volatile vitriolic acid: this indicates the decompofition of part of the fulphur and the union of the phlogifton with the calx, before the remaining fulphur could combine with it. 5. It tinges microcofmic falt of an elegant green colour on charcoal by the aid of the blow-pipe. Borax appears cineritious when viewed by a reflected light, and of a violet colour when feen by a refracted light. 6. This calx may be reduced by phlogifton to the state of a complete metal. By thele properties which plainly indicate a metallic earth of an acid nature, my conjecture concerning the radical acids of metals is greatly strengthened: this is the firft example of a structure analagous to that of arfenic. A perfect dephlogistication of the acid has not been yet accomplished. Lapis ponderofus noticed by Cronstedt, fhould be carefully diftinguished from the heavy par which confifts of the heavy earth and vitriolic acid. They agree in being both heavy, but are of a totally different nature. In 1779, I inveftigated the principles of the lapis ponderofus, and found them to be calcareous earth and a peculiar acid. Mr. Scheele unacquainted with my experiments, afterwards in 1781, defcribed this acid. It affords a white acid earth like that of molyb dæna, differing however in feveral refpects; the chief difference confifts in the acid of molybdæna, not recompofing lapis ponderofus when faturated with calcareous earth. I fhall foon point out other inftances of difagreement. The indications of its metallic nature and acidity are: 1. The fpecific gravity, which is, 3, 600. 2. Its powdery form and acid nature, 20 parts of boiling water take up 1; the folution has an acid taste, reddens tincture of turnfole, and precipitates the folution of hepar of a green colour. 3. The precipitate caused by phlogisticated alkali, is white and foluble in water. 4. Distilled with fulphur it acquires an afh-colour, but in other refpects is little changed. 5. It tinges microcofmic falt of a pure azure, and when the rays of light pafs through it, there appears no mixture of red; a larger dofe of earth produces a dark, and at length a black hue. Borax does not affume fuch a pure azure when treated with this earth. Lapis ponderofus is exceedingly fcarce in Sweden, on which account neither perfect dephlogistication nor reduction has yet been attempted. Of the acid of fiderum I have treated before.-As we have then three fubitances befide arfenic which refemble metallic calxes in their specific gravity, powdery appearance, property of tinging fluxes, in being precipitated by phlogifticated alkali, and being capable of being reduced, and thew an acid nature in being foluble in water, in their acid tafte and power of reddening tincture of turnfole, my opinion concerning radical acids does not reft on one but on four inftances, which render it highly probable. The white colour of thefe calxes is perhaps deferving of particular attention. I have elsewhere obferved that the white calx of zinc does not altogether elude the power of dephlogifticating fubftances, fince they turn it black. It is taken up by alkalis as well as that of antimony, which feems to be in fome meafure foluble. He who is defirous of labouring in the field of metals that yet remain to be dephlogifticated, fhould begin with thofe calxes, which are moft eafily foluble in alkalis, a property which would feem to fhew that the acid is not fo much involved." We must defer the remaining, which is the larger part of this volume to fome future number; in the mean time we fhall transcribe the titles of the effays, which we are obliged to leave for the prefent unnoticed; On the different quantity of phlogifton in metals; On fulphurated tin; On fulphurated (or crude) antimony; On the productions of vulcanos; On elective attractions with three plates, It is with regret we observe that a small number only of copies has been imported into this country; for we apprehend that this volume is not expofed to fale in any place in London. But we obferve with ftill greater regret that no chemift has yet offered to the public thefe admirable models for conducting experiments, and for deducing conclufions in an English drefs. Four years have almoft elapfed, fince a philofopher of high eminence in France gave the first volume to his countrymen; and the avidity with which the original has been fought in this country, affords a strong pre prefumption that a well executed tranflation would not fail to meet with a welcome reception. ART. XIV. Recherches Phyfiques fur l'Electricité. Par M. Marat, M. D. 8vo. Elmfly. W Enquiries concerning Electricity. E announce this work to the public, becaufe we believe it has never before been done. The reader, who is acquainted with the former productions of this author, will naturally expect to meet with fome new notions, and he will not be difappointed. Dr. Marat is certainly not destitute of scientifical courage; having formerly attempted to overturn the Newtonian doctrine of light, he now combats opinions that are very generally received. He denies the repulfive property, from which fo many phænomena have been explained, to the particles of the electrical fluid; he contends for the permeability of glass, at least of several kinds; he explains the Leyden phial in a manner different in feveral refpects from the common theory, and whatever topic he is treating, he quits the beaten track. ART. XV. De la Verité ou Meditations fur les Moyens de Parvenir á la Verité dans toutes les Connoiffances Humaines. Par J. F. Brillot de Warville. Concerning Truth, or Meditations on the Means of arriving at Truth in every Human Science. Svo. Walter. HIS enterprizing author, who has lately planned a magnificent fcheme for facilitating the correfpondence of the cultivators of fcience, and who publishes a periodical account of British literature in French, here enters upon an extenfive and arduous enquiry. This volume contains only fome general obfervations, and a difcuffion of fome preliminary propofitions. We cannot at prefent enter into a detail of particulars. We however recommend the work to our readers, as written in a lively manner, and containing many ingenious and fhrewd obfervations. Among other opinions he advances fome that are very repugnant to the practice of the present times; every city has now its academy, more especially on the continent, and in every street lecturers are pouring forth the treafures of knowledge, infomuch that there is reafon to apprehend left the world should overflow with wifdom, and while all men are in hafte to give inftruction, there fhould remain none to receive it. But M. de Warville contends, that thefe means are likely to produce very different effects, and are little calculated to add add to the fum of our knowledge. Let the reader confider his arguments. For the ENGLISH REVIEW. A Character of Dr. S WIFT: Embellished with a very fine Engraving of his Head, by Bafire. DR R. Jonathan Swift attained a very high reputation among his contemporaries; and his writings will defcend in triumph to a distant posterity. The times in which he lived were favourable to literature; and men of rank thought it an honour to affociate with the propagators of fcience, and with the poffeffors of wit and learning. This fashion which is reverfed in the prefent age, when politics are every thing, and when letters are neglected, was moft propitious to Dr. Swift. The facility with which it allowed him to mix with the great, advanced his fortune; and he was able to cultivate his faculties at eafe, and to indulge his propenfities and humour. : But his nature did not difpofe him to be happy; and during the greateft part of his life he was in the expectation of being promoted to a bishoprick in England. His noble friends, however, were not altogether certain of his steadinefs they did not with to be under the near inspection of too accurate an obferver; and they were fenfible that his difcretion and prudence were not fufficient to restrain his difpofition to morofenefs and fatire. They paid him, accordingly, a ceremonious deference; and when they confulted him in politicks, they generally gave way to affectation. Their fear of him was greater than their respect, and their attention more than their fincerity. He was often a dupe to the myfterious policy of Lord Oxford, and often offenfive to the oftentatious vanity of Lord Bolingbroke. His mind had taken a gloomy and perverfe direction, and he was too conftantly a prey to unhappy paffions. Difguft, hatred, indignation, contempt gave him a melancholy agitation; and he was apt to communicate to others the irkfomenefs of his feelings and mifery. His writings afford no examples of what is fublime, or elegant, or beautiful. The pictures he draws have a reference to whatever is moft difagreeable and loathfome. The deformities of human life fixed his notice; and he is never fo fupremely happy as in degrading the purfuits and employments of mankind. Yet with this faftidious elevation, he could himfelf defcend to the most trifling occupations, and find a pleafing paftime in puns, obfcenity, and folly The |