manufactured. Sir Benjamin Thompfon very properly attri butes the different effects excited from these different substances, when worn next the fkin, to their abforbing power; the one feels warm, because the moisture is immediately abforbed; the other cold and moift, fince it remains uncombined with the fubftance in contact with the fource of the fluid. The power of woollen, in promoting perfpiration, depends on the fame principle, rather than the warmth.

Art. XXIII. The Principles and Illustration of an advantageous Method of arranging the differences of logarithms, on Lines graduated for the purpose of Computation. By William Nicholfon.This is a feries of computation, and of defcriptions illuftrated by diagrams. The fcale is fimilar to Gunter's, or a circular one, compounded of Gunter's fcale, and a sector; and this improvement promifes to be convenient as well as ufeful.

Art. XXIV. Obfervations tending to fhew that the Wolf, Jackall, and Dog, are all of the fame fpecies. By John Hunter, Efq. F. R. S.-Though Buffon contended that the wolf and the dog would not breed together, yet there are actual inftances that the contrary is true, and that the progeny is prolific. Mr. Hunter has collected feveral of these instances; but we are not certain of the truth of his inferences, that they are of the fame fpecies. It is probable only, that they are of a fimilar kind,, for the inftances are taken from confined animals; and the final caufe can have no influence in the argument, fince the copulation would probably never have taken place in a ftate of nature, and of courfe the world could not readily have been peopled with monfters. The jackall is undoubtedly fimilar to both the wolf and dog and if we can allow that the dog is a wolf tamed,' it may be admitted, that the jackall may probably be the dog returned to his wild ftate.'

Art. XXV. Experiments on the Congelation of the Vitriolic Acid. By James Keir, Efq. F. R. S.—Mr. Keir thinks, that vitriolic acid, of a certain firength, may be frozen by a degree of cold equal to about 45° of Fahrenheit's fcale, and that this ftrength is 1780, at a medium, while water is fuppofed to be 1000. Acids of the ftrength of 1750 to 1814 freeze with greater cold; but, from 1846 to 1551, no congelation takes place in any degree of artificial cold. The acid, in freezing, remains fome time fluid, like water; its heat is ftationary; or, when cooled too much, the heat is alfo increased at the moment of concreting; but the ice is heavier than the strongest acid. As the ftrong oil of vitriol attracts water from the air, and in this operation produces heat, it is,

indeed, probable, that the freezing fhould be at that point where the power of attraction is fo weak as not to excite heat. Indeed, the acid, of which the ice is compofed, when separated and thawed, appears to be of the ftrength of easiest freezing; and our author's argument against this cause of the easiest freezing, is not conclufive.-Yet, on the whole, we think there may be fome other cause of the acid freezing at this determined point, or near it. The congelation was firft obferved in the fmoaking acid taken from martial vitriol; and we have now abundant reason to suspect, that acids drawn from metallic falts have peculiar properties: this confideration led ùs formerly to remark that, in count Lauraguais' experiment, the concretion might be owing to a combination of fome other body. We muft, however, obferve, that Mr. Keir's experiments are confirmed by fome late ones of M. Chaptal, a manufacturer of oil of vitriol, in France. His faleable oil is, however, 66, and the congealable oil 63: our faleable oil is 1846.-If, therefore, we fay 66:63:: 1846: 1762, we shall find the ftrength of the congealable oil in France fome what lower than our author found it. In M. Chaptal's experiments it was congealed at -3 to 1 of Fahrenheit, confiderably below the freezing point. It would be too long to engage in a detail of his experiments: we hope to do it very foon, and that we may even find room for it in this month's Intelligence.

Art. XXVI. An Account of fome new Experiments on the Production of artificial Cold. By Tho. Beddoes, M. D.Dr. Beddoes defcribes the experiments of Mr. Walker, apothecary to the Ratcliff infirmary. By adding, fucceffively, fal ammoniac, nitre, and Glauber's falts, while they held the water of cryftallization, to water, this gentleman funk the thermometer 46 degrees. By employing materials, previously -cooled, the diminution of heat was more confiderable: by adding cooled materials to cooled diluted fpirit of wine, the thermometer was funk to -4. Sal ammoniac, added to diluted fpirit of nitre, defcribed by Mr. Cavendish, at-3, funk the thermometer to 15. Nitrous acid, poured on Glauber's falt, (in crystals, we prefume), produced nearly the effects which it would have had on pounded ice'; while the cold is rendered ftill more intenfe, by adding fal ammoniac, in powder, to the mixture. The proportion of the ingredients is the following: of concentrated nitrous acid 12 ounces, of water 6 ounces: thefe materials must be cooled to the temperature of the atmofphere; and to them must be added a pound and a half (averdupois) of Glauber's falt, and of fal ammoniac 12 ounces. In this way the thermometer was funk full 60°; and, in Z 2 another

another inftance, 68°. By dividing the experiment into dif ferent parts, and fücceffively cooling the materials, Mr. Walker froze mercury, without a particle of ice and fnow, when the heat of the air was at 45; a fact almost beyond the reach of belief. Oil of vitriol, diluted with an equal weight of water, joined with Glauber's falt, produces about 46° of cold. If therefore, in fummer, the water from a deep well is at 52, in this cheap and eafy way it may be brought down to 12°; and wine, placed in it, would be chilled. A curious fact occurred in these experiments: in trying a mixture of two parts of oil of vitriol, and one of water, with the Glauber's falt at the temperature of 35, the mixture appeared to be frozen; and the thermometer was ftationary. This must have happened from the cryftallization of the falt, for the ftrength of the oil was below the point of eafieft freezing. It was plain that fome heat was produced, for the thermometer was stationary; and the heat, at the end of the experiment, not fo great as was expected. The cold produced, Dr. Beddoes thinks, is in confequence of the water of cryftallization from a folid becoming again fluid.

Art. XXVII. An Account of a Doubler of Electricity; or a Machine by which the leaft conceiveable Quantity of positive or negative Electricity, may be continually doubled, till it becomes perceptible by common Electrometers, or visible in Sparks. By the rev. Abraham Bennet, A. M.-This article contains an account of an ingenious method of rendering small quantities of eleârical fluid, in the air, fenfible. The small quantity, collected by a burning torch, a lanthorn, or even an infulated umbrella, by this doubler, became very fenfible. A journal is added of the electrical state of the air, from the 23d of January to the 2d of March: in general, the electricity was pofitive, except in rain; it was then univerfally negative, if we except the rain which arifes from the accumu lation of water in mifts, and is formed from the coalefcence of its particles, As the drops depend on a very different cause in this state of the air from that which produces rain in the ufual form, they cannot be expected to be followed by a change of electricity. The negative electricity feems to be connected with southerly winds, because they are connected with rain: when the rain occurred, as it did in two inftances, with the wind from the north-west and the weft, the electricity was ftill negative. We hope these observations will be pursued with

care.

Art. XXVIII. Some Particulars relative to the Production of Borax. By William Blane, Efq.

Art. XXIX. A Letter from Father Jofeph da Ravato, Prefect of the Miffion in Thibet, containing fome Obfervations

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relative to Borax.-Thefe accounts feem to meet only in one point; that borax is a natural, not an artificial production. In the first, fnow is faid to be requifite to the operation, and the fnow is mixed, for this purpose, with the hot water of the lake in the second, the borax is faid to be procured from rain both accounts agree in the circumftance that falt mines. are in the neighbourhood of the borax pits. The falt is covered with oil or butter, to prevent its deliquefcence. It is brought from Jumlate, a kingdom in the northern mountains, thirty days journey north from Betowle, which is zoo miles N. E. of Lucknow. Lucknow is, however, about 600 miles N. W. of Calcutta; fo that the real distance of the kingdom of Jumlate is increased by this mode of computation. The country cannot be found in the maps; yet, if it is in Thibet, it cannot exceed the 35th degree of north latitude. There are many pits of borax, to which the falt is brought by springs; the hot fprings, in the firft narrative, diffolve it probably in large quantities, and the fnow may be neceffary to cool the water, in order that the falt may cryftallize; while, in the fecond account, if by rain water is understood the rain collected in falling from the neighbouring hills, the evaporation by the fun is fufficient to exhale the fuperfluous fluid. The 29th article is in Italian, but it is tranflated very accurately at the end. The hiftory of borax is an object of commerce, and, as a chemical agent, is very curious and interefting, particu larly as it lies fcattered in various authors, and has never been collected.

Art. XXX. Sur les Gas Hépatiques: par Monf. Haffenfratz. On Hepatic Air: by M. Haffenfratz.-Mr. Kirwan taught us that hepatic air was only fulphur in an aerial state; but M. Haffenfratz found that he could hepatize many different kinds of air, and that the hepatic gas was only fulphurated air of different kinds. M. Mongez had already made fulphurated fixed air: M. Haffenfratz fulphurated also nitrous air, atmospherical mephitis, vital, and atmospherical air. What has been called hepatic gas was the inflammable air fulphurated.

Art. XXXI. Botanical Defcription of the Benjamin Tree of Sumatra. By Jonas Dryander, M. A.-It is fomewhat remarkable, that this tree fhould have been so often mistaken; Ray looked for the origin of an East Indian drug in a Virginian plant: it was then a laurus. Linnæus thought it belonged to the croton; and the croton benzoe flood in one mantiffa, and the thirteenth edition of the Syftema Vegetabilium, p. 721. In the Supplementum Plantarum, it was a fpecies of terminalia, afcertained only by the fimilar appear.

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ance of the barks of these trees (434). Mr. Marsden gave a better account of it; but Houttuyn brought it back again to a laurus (Act. Harlem, vol. xxi. p. 265.) It is now pretty diflinctly afcertained, from a dried fpecimen, to be a species of ftyrax. A good outline of its habit and appearance is fubjoined in a plate.

Art. XXXII. An Account of an Experiment on Heat. By George Fordyce, M. D. F. R. S.-This is an experiment on the communication of heat. We do not well know for what purpose it was tried, or what good confequence will follow from it. The fact is, that iron will communicate heat not fo fast, at first, as air; but afterwards fafter, and in greater quantities. Surely it was well known, that air was a bad conductor of heat: Dr. Fordyce might have learned it from his own experiments in a heated room. In the horizontal part of the chimney of a reverberatory furnace he could not expect to find any very great heat.

Art. XXXIII. An Account of an Observation of the Right Afcenfion and Declination of Mercury out of the Meridian, wear his greateft Elongation, Sept. 1786. By Mr. John Smeaton, F. R. S.-It is not easy to abridge a series of observations and calculations; the refult was, that on the 23d of September, 1786, A. M. at 51 22′ 35′′ mean time, Mercury's right afcenfion was 163° 59′ 21′′, and his declination 7° 44′ 25" north.

Art. XXXIV. A remarkable Cafe of numerous Births, with Obfervations. By Maxwell Garthshore, M. D. F. R. S. and A. S.—The cafe before us is a well authenticated one of five female children at a birth. The woman had been delivered of a fingle child before; and the husband had been in an infirm ftate for fome years, and was, at the time of this prolific birth, dying in a confirmed phthifis; two of the children were born alive, and the whole number were born within fifty minutes, Dr. Garthshore adds fome reflections on numerous births. In the British lying-in hofpitals, the proportion of twins has been 91 births in 18.300 deliveries. In the Westminster dispensary, of 1897 women delivered, the proportion has been one in 80. But in the Dublin lying-in hofpital, it has been one in 62; the average in these kingdoms is 1 in 78. The proportion of twins to fingle children, in Germany, is from about 1 in 65, to in 70; in Paris, about one in 96. The general average is about one in 8o. In this variety there is fome or der; but in triplets, quadruplets, and quintuplets, there is no confiftency, all feems to be accidental. In one inftance, at Paris, where a woman had three children, the husband was a painter, and had been paralytic two years previous to the