whiteness. Tartar and common falt may be added, if a little more polifh is required. This is nearly the fubftance of thefe memoirs, which we have fittered into chemical questions, left we might injure ingenious artists who now live by theie proceffes. We have given nothing which can, we think, materially hurt them, though to the chemists we have faid enough.

What was formerly called the Siberian fpar was fome time fince found to be a mineral of lead. It rites near Catherineburg, at Berefof, where there are alfo mines of iron containing gold, which is feparated from the cubical pyrites, by reducing the iron to a hepatifed ftate. The cryftals of the red lead are rhomboidal tetraedra, he the white and green ores, but lighter, and lofing about a quarter part of their weight when weighed in water. M. M. Marquart and Lehman have examined it in the moift way, and by means of the blow-pipe, as well as in the open air. The refult of M. Marquart's examination is, that it contains 36 parts of lead, 373 of vital air, 24% of iron, and 2 of alum. The little additional weight feems to have arifen from the product having acquired some moisture. The alum M. Lehman calls felenite.

M. Sage has alfo described an earthy ore of lead combined with arfenic and phofphoric acid: its cryftals are prismatic hexaedra; the colour of a yellow green; but this is not owing to any other metal different from the lead. The arfenic is in the proportion of about half, and the lead in about one tenth.

M. Hyelm has given a very scientific defcription of his method of reducing molybdena. It has been doubted in France, whether this was really a metal, or an earth diftinguished by peculiar appearances, in confequence of its union with the vitriolic acid. Our author has fhown how to feparate the acid, by repeatedly pouring olive oil over it, and burning them toge ther, which changes the acid into a fulphur, and diffipates it in vapour. He shows alfo how to reduce the molybdena, by uniting it with other metals, whofe volatility and inflammability are in this way increased, and by different fluxes, which produced the regulus defcribed by Scheele and Bergman. Thefe details we cannot eafily abridge: when melted alone or with powdered charcoal, and the nafs is afterwards triturated, the Imall particles feemed to fhow fome brilliancy, but did not appear to be decidedly metallic.

As we proceed in a retrograde courfe, we fhall next mention. the earths fo far as relates to their chemical history, or their artificial decompofition by heat and moisture. M. Sage has added fome farther obfervations on the fappare, a stone whose compofition we defcribed from M. Sauffure's analysis, in our last volume, p. 383. M. Sage has defcribed it in the fecond volume of his Analyte Chymique, p. 71. in the following terms. In the granites of Spain, and in thofe of St. Symphorien, near Lyons, we meet with a kind of an aigçe marine, of a

blue

Blue colour, in long flattened tetraedal prifms, foliated in a longitudinal direction, and fometimes united in bundles. He afterwards received, he tells us, fome of thefe foliated berils from mount St. Gothard. They are found in a white transparent quartz moulded on the crystals. They are alfo met with on white opaque felt fpar, mixed with fleatite: fometimes the quartz, and felt fpar are coloured by ccrc. The berils, from different countries, nearly refemble each other: in a group of crystals from Germany, a rhomboid was very diftinguishable. The foftnefs, described by M. Sauffure, is only in the direction of the lamella; in a contrary one it strikes fire with steel, when the crystals are not exfoliated, or the laminæ divided by fteatite. It does not lofe this property by calcination; and the furface, in confequence of the heat only, becomes of a pearly whiteness. The colouring iron may be extracted, we find, by powdering the stone and diftilling it with eight parts of fal ammoniac, which fublimes without decompofing, and the lixivium of this falt-work, with the phlogisticated alkali, depofits Pruffian blue. M. Sage, we perceive, continues to think the ting. ing principle of Pruffian blue an acid, and the neutrals formed by it, kept in his poffeffion fome years, are not, he obferves in another memoir, deliquefcent. Our author fufpects that the magnefia which M. de Sauffure found, came from the steatite.

A new felt fpar, ftyled the adularia, has been discovered on the Stella, near St. Gothard, by M. Spini. Of this family we were only acquainted with the common felt fpar, the Labrador ftone, and the pierre de lune. The adularia is, like the other fpecies, foliated; its fracture rhomboidal; its fragments rhomboids, four furfaces of which reflect the light, though the four other furfaces have not this property. Its colour (that of mother of pearl) diftinguishes it from the com mon felt fpar. It is cat's-eyed fometimes, like the Labrador ftone, but the colours have not the fame brilliancy or intensity, and feem owing to fome oblique imperceptible fiffures, fuch as occur in glafs alternately expofed to the rain and to the fun, when it is beginning to exfoliate. Betides, the Labrador flone is always of a greyish caft. It is more difficult to distinguish it from the moon-ftone, which appears of a clear fler colour, when the light is viewed through its thin laminæ, and is fomewhat tranfparent; circumstances not observed in the adularia. It is harder than common felt spar, and lefs hard than quartz: it is cold to the touch, with difficulty fcraped. with the knife, and generally strikes fire with fteel. Its weight varics, as, it is more or lefs transparent and friable; generally. between 2,550, and 2,600. It is not attacked by acids; it neither decrepitates or becomes phosphoric in the fire; it runs to a white glafs filled with little microfcopic globules; in the dry way it is diffolved with effervefcence by means of borax, and imperfectly, without effervefcence, by mineral alkali. In mountains, it forms firata between thofe of the faxum fornacum and

Kk3

veined

veined granite: it may, like other felt fpars, occur in threads or be a component part of other ftones. Our author, M. Struve, thinks it only a variety of common felt fpar and related to it, as the Iceland fpar is to the common calcareous fpar. Its analyfis has been given differently. M. Morell found in 100 grains, 13 grain of water; of fiint 627; of clay 1991; magnefia ; of felenite 1017; but he fpeaks, with diffidence, of his real fuccefs. The white felt fpar contains more flint, lefs clay, and terra ponderofa, inflead of lime.

M. Dodun has added to our knowledge of this fubftance, by deferibing the fpecies found in the black mountain in Languedoc. He thinks M. Struve too rafh in calling it a felt spar, because to the form of cryftallization the fame integrant parts fhould be added. The adularia of Languedoc is found in the fiffures of the black micacious granatoid rock, following its calcareous bands, which alternate with the granatoid. It is in thefe fiffures, which contain the elements of the matrix, and in which the adula ia feems a fecondary formation, that it must be chiefly fought; but it is by no means fo transparent as that deferibed by M. Struve. This fpecies is harder than felt fpar and lefs hard than quartz: it with difficulty ftrikes fire with feel, though fteel does not injure its folid angles. Its faces are veined with a dirty white, and with green, more or less deep; in fome places cats-eyed. The fracture is like that of quartz, but not very brilliant: it laminated structure is only afcertained by the help of the microfeope. Borax does not dif folve it with effervefcence, on a fupport of charcoal. A fire of half a hour's continuance is neceffary to fufe a piece not larger than the head of a pin; and it appears in borax as a white fpot, not unlike opaque quartz. The glafs is of a greyish white, with many fine microfcopic cellules. M. Dodun has not yet analyzed it in the moift way.

Another mineral, whofe nature we have lately underfood more accurately, is the Prehnite of Werner, fo called, because it was given him at the Cape of Good Hope, where it occurs, by colonel Prehn. This mode of denominating cryftals is justly reprehended by M. Sage, to whom we are indebted for our information refpecting its analyfis. The latter formerly called it the chryfolite of the Cape; but, on more accurate enquiry, found it to be a fchorl. It is the No. 81 of the cabinet of the royal fchool of minerals, thus defined: 'a green clear tranfparent fchorl. lamellated, firiking fire with feel.' In the fire, it foon lofes its transparency; when the heat is increafed, it fwells, and produces a greenifh brown cellular enamel, which does not concrete in maffes. The colouring matter is iron, and it is difcovered by the fame procefs as in the fap. pare. Werner would clafs this green tone of the Cape between the zeolite and the fchorls; M. Jacquet calls it a cryf tallifed prafos; M. Bruckman thinks it a felt fpar; M. Halfenfratz has defined it in the following manner; a flinty, cal

Carcous,

careous, aluminous, magnefian, iron-ftone, of a green colour in laminated males, femitransparent and crystallized in bundles on the furface.' On analyzing, he found it to contain of flint 50; lime 23.4; alum 20.4; calx of iron 4.9; water 9; magnefia 5. M. Klaproth's analyfis differs only in the proportions, and his not difcovering magnelia. It contains, according to this author, of flint 43; alum 30; lime 181; iron 53; water and air

M. Bournon formerly defcribed the pechtein of Menil montant, which has been found to contain magnesia; but, as other flones, apparently of the fame kind, produced no bitter falt, when treated with vitriolic acid, philofophers were inclined to exclude this fpecies from the clafs. Mr. Bournon, though he allows it to differ in this respect, yet thinks it agrees in fo many others, as to deferve the denomination. He retts, however, on its containing only a bituminous matter, which he connects with his own fyftem of lithology; but, in this part of his memoir, the proofs feem to be defective. He calls that oily fubftance which in the mother water prevents cryftallization, the mineral fat. Onfimilar grounds, he connects the hydrophanous ftone with the pechftein, calcedony, fardonix, opal, agate, jafper, filex, and petro filex.

M. Afzelius Arvidfon has defcribed the different kinds of heavy fpar found in Sweden, and added an analysis of each. The fpecific gravity varies from 4.583 to 3.892. They contain a pretty large proportion of pure heavy fpar, from 93 to 55 parts in 100; but the average proportion is about 65, fome pure felenite, a little pure vitrifiable earth, fome ocrous clay, a very little water, and occafionally fome aerial fubftance of an uncertain nature. One kind does not contain the felenite, and another, with the felenite, has about .08 of aerated calcareous earth.

We fhall conclude our sketch, fince an account of the other objects of chemistry would at prefent lead us too far, with a tranflation of one or two of M. Crell's letters to M. D'Arcet and M. de la Matherie: they are as ufual, interefting and inftructive, though concife and abrupt. The firft is to M. D'Ar

cet.

Sir, M. Schiller wrote me, fome days fince, that, by mixing one part of fal ammoniac, three parts of potash, with one part and a half of water, difilling thefe ingredients, till all the cryftallizable falt had paffed over, and then changing the receiver, he obtained a liquid, which appeared, in every refpect, like the beft phlogiflicated alkali. I have a curiolity to examine, if this happens with every kind of fal ammoniac, or is peculiar to that of Egypt, which fill contains fome particles of the foot unmixed. M. Weftrumb has analyzed the calculus from the bladder of a horfe, and the incrullations of chamber pots, without finding the acid difcovered by Scheele, Bergman, and Brugnatelli. But, befides a confiderable quantity of oily

Kk4

phlu

phlogion, he found fome volatile alkali, calcareous earth, and phosphoric acid. This chemist has alfo analyzed different fpecimens of fulphur from the fhops, and has difcovered in it fome arfenic and a little calcareous earth. The prefence of arfe. nic is calily explained; but the calcareous earth, which is found even in the flowers of fulphur, is it a constituent part, or even the base of phlogifton? the quetion is yet undecided. The next is to M. de la Metherie.

M. Weftrumb has proved by new experiments that all the vegetable acids, when the analyfis is carried to the utmost point, yield plofphoric and aerial acids. These are obtained by employing nitrous and dephlogifticated muriatic acids. If the vegetable acids are treated with pure nitre, he finds the phofphoric acid alone: he will foon publifh the proofs of this very new difcovery. I have feen with pleasure, from your letter, that the antiphlogistic theory makes no progrefs in foreign countries; that, on the contrary, it feems to lose ground, If Dr. Priestley's new experiments be farther confirmed, of which I entertain no doubt, this theory will lofe its fupport; and we fall only find the numerous difficulties which have been already objected to it.

MONTHLY CATALOGUE.

FRENCH AFFAIRS.

The Speech of Mr. Necker, Director General of the Finances, at the Meeting of the Affembly of Notables, held at Verfailles, November 6, 1788. To which is added, the King's and the Kerp er's Speeches. 8vo. 15. Debrett.

HE Speech contains in embryo the future organization of Tthe of the the affembly of the ftates-general. It rather propofes fub. jects of deliberation, than offers any decided opinion. It is flight, pompous, and unimportant.

Mr. Necker's Report to his moft Chriftian Majefiy in Council, an nouncing important Changes in the French Government. Tranf lated from the French. 8vo. 15. Debrett.

In the Report before us, the comptroller of the finances fpeaks more openly; but his advice of increafing the number of commons, and of admitting at least of a thousand deputies, has laid the foundation of the liberties, perhaps of the continued anarchy of France. Each propofal was equally injudicious. Extrait de la Requête Addreffe au Roi par M. de Calonne, Miniftre a'Etat. 8vo. 25. Robfon.

In the struggle with clamorous authors, and numerous important English publication, M. Caloune's Requête au Roi efcaped us; and, when we turned to it, we had little tempta tion to enlarge on a political debate, which, at that time, ap

peared