respect to the water spout, he adopts, as the most probable, the opinion of the celebrated BECCARIA, who confiders it as the effect of the electrical power of the atmosphere. The following reafons are alleged in fupport of this hypothefis. First, the fpouts are, for the most part, formed during thunder-ftorms, and confequently, when the clouds are the moft charged with electricity,-lightnings have been fometimes obferved flashing with prodigious celerity about the water-spout,-attractions and repulfions of drops of water or other corpufcles, have been obferved under the spout or the cloud whence it proceeded, which refembled electrical attractions and repulfions in a ftriking manner; and laftly, according to BECCARIA, there are obfervations which teftify, that these meteors have been averted or diffolved by the elevation of pointed conductors, which are faid, by the fame author, to be in general ufe among mariners, in those parts of the world where water-fpouts are frequent.-From thefe data M. VAN MARUM thinks, that fome progrefs may be made in the theory of the formation of this meteor, though they may not furnish a perfect explication of its nature. The earth, fays he, mult attract the electrical clouds that are at a small diftance from it; this attraction muft neceffarily exert its power on the lower part of the cloud, and hence that part approaches the earth in the form of a column or cone; but as the watry particles of the cloud are more powerfully attracted than the particles of air with which they are intermixed, the water muft, of confequence, be accumulated in the lower part of the column, and as the weight of the column is thus continually increafing, it at length falls of a fudden by its own gravity. He obferves farther, that if the water-fpout be an electrical phænomenon, or the effect of electricity, the rifing of the water under it, and the violence with which it carries up bodies from the furface of the earth, must be derived from the fame electrical power, and not from a gyration of clouds by contrary winds, meeting in a point or centre (as has been generally imagined), and falling down, where the greatest point of condenfation is, into a tube, somewhat like the fpiral fcrew of Archimedes, which abforbs and raifes the water by its whirling motion. The electrical production of whirlwinds has long fince been rendered probable, by the observations of M. Wilke, in a differtation concerning contrary electricities, publifhed at Roftock; and our Author adopts both the opinion and the arguments of that ingenious naturalift. He alfo locks upon it as highly probable, that the aurora borealis is nothing more than the electrical Auid, which diffufes itself in the higher and more rarefied parts of the atmosphere. On this head doctors differ, and fome doctors of note, fuch as the ingenious and learned profeffor of Franeker, M. VAN SWINDEN, are not of our Author's opi. пісп. ion. Great authorities, it is true, engaged M. VAN Marum to feek the explication of the Aurora in the principles of electricity, and, for aught we know, it may be the true method: His reafons contain nothing new they are a fummary of what Beccaria, Meffier, Canton, Franklin, and Hamilton, have offered on the fubject. The SECOND ARTICLE in this, volume, is a differtation on dephlogisticated air, and the manner of obtaining it, and rendering it ufeful in refpiration. By JOHN INGENHOUSZ, M. D. The ift part of this memoir contains general reflections on the falutary effects of dephlogisticated air in several diseases, occafioned or increafed by breathing an air more or lefs corrupted by putrid exhalations. The fubftances from which this air may be obtained, and its peculiar properties, when obtained from different bodies, and by different methods, are largely treated in the 2d part. In his Experiments on Vegetables, published in 1779, Dr.. INGENHOUSZ had fhewn an expeditious, cheap, and plain method of obtaining, during the fummer-feafon, large quantities of dephlogisticated air, by means of the most common plants. But in the winter it must be obtained from green vitriol, minium, red precipitate, and nitre. The method of procuring it from the laft of thefe fubftances, is the most expeditious and the leaft expenfive. But to obtain it in all its purity, and without any mixture of fixed air, care must be taken to shake it in water, in order to wash and purify it. Another precaution used by our Author is, to hold the wick of a candle, newly blown out, near the cock of the glafs-receiver; in which cafe, if the candle be re-lighted, and refumes a vivid flame, it may be concluded with certainty, that all the fixed air has paffed. It appears also, from the experiments here defcribed (which Dr INGENHOUSZ made according to the method indicated in his Treatife on the property of vegetables to purify the air) that the firft air which fucceeds the fixed air is always the pureft, and that the purity diminishes in proportion as the operation draws near to its conclufion *. The 3d part of this differtation treats of the manner of obtaining dephlogisticated air from nitre. Our Author's method is ingenious, and by this time well known to the curious, as we fuppofe. The 4th part is employed in pointing out the manner of breathing with facility dephlogisticated air, and of disengaging it from the fixed air with which it is charged by paffing through the lungs Our Author does not approve of Fontana's method of ufing this air, becaufe, by obliging the breather to stop his Dr. Ingenhoufz gives, under this article, a curious and inftructive table of the different degrees of purity, announced by his eudiometer, in the examination of dephlogisticated air, drawn not only from nitre, but also from other fubftances, mineral and vegetable. Sf2 noftrils, noftrils, the acts of infpiration and exfpiration are rendered fatiguing. After having, therefore, tried the experiment in different ways, he prefers the following: take two large bladders, cleanfed from their fat, and well dried; rub them with fresh butter, or olive oil, that has no fmell, to render them foft and durable: prepare a copper tube, of three or four lines diameter; at one end of it place à cock, and fit to the other end the neck of a fmall bottle of caoutchouc, or elaftic gum, at least three inches' long, and as much in breadth. By feveral operations which our Author defcribes, and which may eafily be conceived, this piece" of elaftic gum may be fo fashioned, as to fit the nofe exaЯly,, and to fit fo clofely to the fkin, on all fides, as to prevent entirely the paffage of the air. When all this is done, one of the bladders, filled with dephlogifticated air, is to be fitted to the" tube above mentioned, with one hand, and the cock of the tube. must be opened with the other, while all poffible care is ufed to keep the elaftic refin fo close about the nofe, that the air may not be allowed to pafs. If the bladder contains nearly 250 cubic inches of dephlogifticated air, of a good quality, it may be used in 16, perhaps 20 inspirations and exfpirations, before it be so far diminished in its purity as to be of an equal quality with common air. Our Author made a great number of experiments, to a certain the degree of diminution in quality that dephlogifticated air suf-` fers by the action of the lungs. From thefe it appears, that the quantity of this air that is neceffary to a fingle infpiration, does not become inferior in quality to common air, until it has been four times expofed to the action of the lungs: the 5th inspiration can add little alteration, fince it is already overcharged with fixed air and phlogifton. How the dephlogifticated air, thus diminished in quality, may be restored to its former purity, by making it pafs through water, and more especially through lime-water, our Author fhews at great length; and the different proceffes he has employed for this purpose, are here as accurately defcribed as they are ingenioufly contrived. But for an account of them we must refer the curious to the work itself. M. INGENHOUSz is of opinion, that, to obtain any palpable advantage from this air in medical cafes, the quantity of it daily employed muft amount to at least 1000 or 1200 cubic inches. According to the method indicated above, this quantity may ferve for between 100 and 120 infpirations. In inflammatory, putrid, and other diforders, the dephlogifticated air may be fooner charged with phlogifton than in other cafes, and muft therefore be renewed more frequently. Our Author has found remarkable benefit from this air himfelf; after taking a certain quantity of it, his cheerfulnefs, ftrength, and appetite, were increafed, and his fleep was more calm and balmy than ufual.. In the 5th and laft part of this differtation, the Author lays down a compendious method of ascertaining the degrees of purity in dephlogifticated air. It is well known to what a high. degree of fimplicity and perfection M. de Fontana improved the eudiometer; neverthelefs, when dephlogisticated air is drawn from a great number of different plants, a fingle trial of its quality requires feveral operations: Our Author, therefore, after long endeavouring to find out a method of rendering this trial as expeditious as that of atmospherical air, hit upon one that fucceeded to his mind, and defcribes it here.circumftantially but for an account of this method, and fome anatomical memoirs that follow this differtation, we muft refer our Readers to the work. ART. X. Recueil des Memoires fur la Mechanique et la Phyfique, i. e. A Collection of Memoirs, relative to Mechanics and Phylics. By the Abbé. ROCHON. Member of the Royal Academy of Sciences at Paris, and of the Marine Academy. Svo. 284 Pages, with nine Plates. Paris, 1783. THE HESE Memoirs have every kind of merit that can be ex-. pected in a publication. of this fort. Their Author is a man of eminence in the sphere of practical philofophy. They were all read either in the public or private affemblies of the Academy of Sciences, and they met with the univerfal approbation and applaufe of that learned body. They are all commendable on account of their utility, and most of them are fo from their novelty. In one of the fe memoirs, the author gives, the construction of an inftrument that may be of great ufe in abridging the calculations requifite for the determination of the, longitude in voyages. In another he gives an account of thofe inftruments of his invention, which he calls prifmatic telescopes. (lunettes à prifme) which are defigned to meafure angles, and may be usefully employed, in aftronomy and topography. The experiments and obfervations by which he proves, in another very curious memoir, that the light of the fixed stars, and that of the fun, are of the fame nature, feem as conclufive as they are entertaining. The method he indicates, in another piece, of diftilling in vacuo, is commodious, and adapted to diminish. confiderably the expence of that operation. He has alfo invented a machine, by which beautiful plates for printing may be engraven with great celerity, at a very moderate expence, and to as to unite all the advantages of the Chinese method of printing. The optical memoirs contained in this volume, are peculiarly interesting, and exhibit feveral new experiments and obfervations relative to vifion. ART. XI. Voyages, autour du Monde, et vers les deux Poles, par terre et par mer, &c. i. e. Travels round the World, and towards the two Po'es, by land and fea, from the year 1767 to 1776 inclufive. By M. PAGES, Knight of the Ro, al and Military Order of St. Louis, and Correfpondent of the Academy of Sciences at Paris. 2 Vols. 8vo. Containing 704 pages, enriched with Maps. Paris 1782. Price 12 Livres, bound. HE TERE we have a Traveller who will command attention, even after the great number of those that have been running about the world in the prefent age. M. PAGES followed a method of coming at the knowledge of men and things, in which he had few examples to imitate : he had fufficient refolution of mind, and strength of body, to live long in countries, and among people, whofe fociety would be more than irksome to our rapid travellers, who love their eafe, and would fatisfy their curiofity with as little fatigue and felf-denial as poffible. He was more especially defirous to contemplate, attentively, human nature, in thofe places where it feems to have departed leaft from its primitive fimplicity; and it appears alfo to have been his opinion, that he would find it more benevolent in its rude ftate, than amidft the refinements of civil fociety. This opinion, be it juft or erroneous, does honour to the heart of the man who entertained it; and a multitude of things in thefe travels unite to give us the most favourable idea of the feelings and character of M. PAGES. His relations of what he obferved or difcovered, have been received with high approbation; they are published with the privilege of the Academy of Sciences, and every thing announces, that the three voyages contained in this work, were undertaken, by our Traveller, from a laudable curiofity after knowledge, and a defire to be useful to his country and to humanity. 3 His firft voyage was the tour of the globe, by the way of North America, the South Sea, the Indies, and Arabia. In 1767, he fet out from St Domingo for New Orleans, from whence he failed up the M ffiffippi and the Red River, where he had many obftacles to encounter, from the rapidity of the current, and the trunks and bodies of trees that obftructed its paffage. Here he made an excurfion of above three hundred French leagues, into the country of thofe, fays he, whom the Europeans call favages; and verified, by an attentive observation of their characters and feelings, his favourable opinion of human nature. He relates affecting inftances of their fentibility and fympathy, of their parental and conjugal tenderness, of their refpect for the aged, of the tears they fhed upon the tombs of their departed friends. Among others, he tells us a story of |