however, in a great measure prevented, by combining acids with the oxyds; because, in this cafe, there is a change effected in the elective attractions: the influence of this alteration will be evident to those who try the experiment with the different oxyds of mercury. The reciprocal decompofition of metallic oxyds and ammoniac is fo greatly accelerated by heat, that in fome cafes it takes place inftantaneously with a violent detonation; as in the fulmination of the ammoniacal oxyds of gold and filver, either by fire, or by a flight degree of friction. All these various phenomena depend on the attraction of the principles of the oxyds by thofe of ammoniac, and on that of acids by both thefe compounds. It is M. FOURCROY'S intention more particularly to investigate these attractions with refpect to each metallic oxyd; and, for this purpose, he has already performed a number of experiments on the decompofition of mercurial falts, which will be the fubject of a future - memoir. Memoir on the Detonation of Salt of Glass, when thrown inte Water while in fufion. By M. FOUGEROUX DE BONDAROY.. This substance is known among our workmen by the name of glass gall: if any of it happen to adhere to the ladle, when dipped in water, it will explode with great violence; and dreadful accidents have fometimes refulted from not taking care to dry the ladle before it touches the metal. The prefent academician obferves, that this detonation never takes place, except when the flux has been prepared from fuch plants as contain fea-falt; of this kind is the Fucus maritimus vefic. hab. of Tournefort, which is much ufed for this purpofe in the glasshoufes of Normandy and Bretagne. The falt of glass, made with foda of Alicant, contains only vitriolated tartar and magnefia, and never explodes. Memoir on the Art of Eliquation, or feparating Silver frem Copper by Means of Lead. By M. DUHAMEL. We have here a very minute account of every part of this process, with a defcription of a new furnace invented by the author of the memoir. As it cannot easily be abridged, without tranfgreffing the limits to which we are confined, we must refer those who wish for information on this fubject to the work itself. Obfervations on the Process of making Alum by an immediate Combination of its conflituent Principles. By M. CHAPTAL. This memoir is the ufual annual contribution of the Royal Academy of Sciences of Montpellier, and contains some useful bints. It is well known that the procefs in queftion confifts in exposing the alumine to the action of the fulphuric acid: but as this acid is only a combination of water with the vapour arifing from the combuftion of fulphur, and is much more active in its elastic, than in its condenfed ftate, M. CHAPTAL has found that much expence may be faved by expofing the calcined alumine to this vapour, inftead of the concentrated acid. The lead, with which the apartment, or, as the workmen call it, the house, is lined, in which the process is carried on, is another expenfive article; and this ingenious academician, after many trials, difcovered a varnish which anfwers the purpofe equally well: it is made of equal parts of pitch, turpentine, and wax, melted together, and must be applied boiling hot. He defcribes the house, in his alum works, as 48 feet long, 44 feet broad, and 27 feet high; to line this with lead would not coft lefs than 800,000 livres; whereas, by using the varnish, which has now ftood above two years, the expence was not feven thousand. This varnish is impenetrable by water, and is not liable to crack; it is lefs viscous than tar, makes a smoother furface, and may be thickened, when neceffary, by the addition of brick duft. Memoir on the Combination of Metallic Oxyds with Alcalies and Lime. By M. BERTHOLLET. It was formerly fuppofed that all thofe bodies which, by combining with acids, form a new substance, were of an alcaline nature: but M. BERTHOLLET has here fhewn, by a variety of experiments, that metals, combined with oxygen, form compounds which will eafily unite with alcaline fubftances, and, with thefe, conftitute falts; fo that those metals, which are foluble in acids, and, in this combination, have acquired in fome measure the nature and action of alcalies, become, when oxygenated, a fpecies of acids, and, as fuch, contribute to the formation of faline fubftances. NATURAL HISTORY. Memoir concerning the Nutmeg Tree, or Myristica. By M. DE LA MARCK. We have already given an account of fome microscopical obfervations on the flowers of the nutmeg, by which they were found to be hermaphrodites*: but M. DE LA MARCK, on the authority of M. CERE, director of the King's gardens in the Ifle of France, defcribes them as belonging to the clafs of dioecia, and has given feparate plates of the male and female flowers; which have a monopetalous trifid calix, without any See vol. iii. of the New Series of the Monthly Review, p. 502. corolla. No lefs than eight species are here described; and we are informed that the myristica aromatica is cultivated with great fuccefs in the Iflands of France and Bourbon, and produces fruit not inferior to the nutmegs of the Moluccas. Obfervations on the Species of Fucus that grows on the Coaft of Normandy. By M. LE GENTIL. This gentleman found that the ftem of the Fucus Palmatus has generally an elliptic cavity, about five or fix lines deep, near the root, which is the abode of a kind of petella of an olive colour, like that of the plant. Inquiry concerning the Shrub known among the Ancients by the Name of the Lotos of Lybia. By M. DESFONTAINES. It is here maintained that this vegetable, which is very different from the lotos of Egypt, is that fpecies of jujube which Linné calls the ramnus lotus: its fruit refembles that of the common jujube, but is larger, and of a more agreeable flavour. ASTRONOMY AND GEOGRAPHY. Concerning the Solar Eclipfe, June 15th, 1787. By M. MON NIER. From his obfervation of this eclipfe, which, in Paris, commenced at 4 27′ 25′′ true time, on the western limb of the fun's difk, about five degrees below its horizontal diameter, M. MONNIER infers that, in the lunar tables ufed by the Board of Longitude in London, the moon's place is ftated as too forward by 421". Comparative Obfervations of the Solftitial Altitudes of the Sun. By the fame. In the year 1738, M. MONNIER obferved, by means of a gnomon which he had conftructed in the church of St. Sulpice in Paris, the difference of the fun's altitudes in the fummer and winter folftice: from fimilar obfervations made in 1788, he concludes that the obliquity of the ecliptic is now ten feconds less than it was half a century ago. Extract from the Aftronomical and Phyfical Obfervations, made at the Royal Obfervatory, during the Year 1788. By Meffrs. CASSINI, NOUET, DE VILLENEUVE, and RUELLE. This memoir confifts of aftronomical and meteorological tables, to which we must refer our aftronomical readers. On the Inferior Conjunction of Venus, August 7th, 1788. By M. DE LA LANDE. From the observations made by the Duke of Marlborough, Dr. Hornsby, and Dr. Mafkelyne, M. DE LA LANde, who was was at that time in England, computes the place of the aphelion of Venus to be ro figns 8° 26. Fourth Memoir on the Parallax of the Moon. By M. DE LA LANDE. On the apparent Diameter of the Moon. By the fame. The former memoirs on the moon's parallax were published in the tranfactions of the academy for the years 1752, 1753, and 1756. M. DE LA LANDE had then adopted M. Bouguer's hypothefis relative to the figure of the earth, and hence calculated the conftant parallax for Paris to be 57′ 3′′: but being convinced, by a number of experiments and obfervations made fince, that the fpheroidism of the earth is not more than Jooth, he computes the conftant parallax to be 56′ 58′′. 3 for the latitude of Paris; 57' 5" under the equator; 56′ 53′′,2 at the pole, and, taking the mean radius of the earth, he reckons it 57' 1". Hence the moon's diameter is 32" 47", 3, when the parallax at Paris is 60'. Concerning the Diameter and Light of the Fourth Satellite of Jupiter. By the fame. As objects become imperceptible when their diameters are viewed under too fmall an angle, it is obvious that the apparent will be greater than the real duration of eclipfes of Jupiter's fatellites this difference is variable, and depends on the diftances of Jupiter from the fun and earth, on the brightness of the planet arifing not only from its afpect, but also from its elevation above the horizon, and on the aperture of the telescope through which it is viewed. M. De Fouchy proposed a very ingenious method of afcertaining this difference, by applying diaphragms to the telescopes. M. Bailly put this idea into practice with refpect to the three firft fatellites, and pubblished a memoir on the fubject in the hiftory of the academy for the year 1771. M. DE LA LANDE has here applied the fame principles to the fourth fatellite, and has given formulæ by which the inftant of immerfion, the diameter of the fatellite, and the proportion of its invifible fegment to the whole disk, may always be found. In the fixty-third volume of the Philofophical Tranfactions, is a letter from M. Bailly to Dr. Mafkelyne, communicating the particulars of M. De Fouchy's invention *. On the Satellites of Saturn. By the fame. This memoir contains the obfervations and elements from which its ingenious author calculated the new tables of thefe *See Monthly Review, vol. 1. p. 353, and vol. li. p. 628. fatellites, published in the Connoiffance des Temps for the years 1791 and 1792. Memoir on Solar Eclipfes and Occultations of Stars obferved in the Years 1787 and 1768. By M. De la Lande. Memoir on the Eclipfe of the Sun, August 16th, 1765, obferved in Rome. By the fame. The defign of thefe two memoirs is to afcertain the longitude of the feveral places where the obfervations were made. The following are the principal results: Difference of meridian between Paris and Verona, Gotha, 34′ 42′′ 33 33 Bagdad, Leuenthal, Leyden, Perinaldo, Warsaw, St. Peter's, Rome, Gothaab, on the west coast of Memoir concerning the Variation of Light 2h Ꮒ 47′ 58′′ 26' 8' 21' 30% 1h 14′ 30′′ 3 36′ 26′′ in the Star Algol. M. DE LA LANDE, in confequence of comparing his own obfervations of this phenomenon with thofe of M. Goodrick and of M. Wurms of Nurtingen, determines its period of variation to be 2d 20h 49′ 2′′. Theory of the Satellites of Tupiter. By M. DE LA PLACE. This memoir contains a complete theory of the feveral perturbations of Jupiter's moons, with the analytical calculations neceflary for correcting the tables of their motions. Obfervations on feveral Monuments of ancient Gothic Architecture in Paris, on which are carved the Signs of the Zodiac, together with fome Egyptian Hieroglyphics relative to the Worship of Ifis. By M. LE GENTIL. Defcription of the Signs of the Zodiac in the Benedictine Abbey at Saint Denys. By the fame. Obfervations on a Differtation written by M. De la Lande, inferted in the Journal des Sçavans for July 1788. By the fame. M. LE GENTIL obferves, that the figns of the zodiac here defcribed have a great refemblance to those which have been difcovered in India: hence, and from the fimilarity between the ancient Gothic and the Indian ftyle of architecture, he con jectures |