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son to suppose, that the urn contains the ashes of some lady, ilJuftrious in her time and day. The two last plates of this Number represent two tombs or sarcophagi, of noble workmanship, and a fingular capital of the Corinthian order, with cornucopias instead of volutes, and in the middle a medallion exhibiting a female head, with Aowing tresses, and some very elegant figures on the base of the column. These antiquities were observed by our Author in the episcopal palace of Monreale.
ART. IX. Verbandelingen van het Bataafsch Genootschap, &c. Transactions of
ibe Batavian Society at Rotterdam. Vol. VI. HE first piece we find in this volume is the differtation of
Dr. VAN MARUM (a very ingenious and learned phyfician at Haarlem, and known with diftinction in the walk of experimental philosophy), which obtained the gold medal, as the best discourse on the following question: To shew by proofs, what meteors depend upon the operation of natural electricity, how such meteors are produced by it, and what are the best means of preserving houses, tips, and persons, from their pernicious effects. This dissertation is divided into fix parts,
In the first the author News that lightning is an effea of the natural electricity of the atmosphere, and may be considered as the discharge of the electrical force of the clouds, by seven properties, which lightning has in common with electricity, such as its serpentine motion ; its direction to those bodies, which are the best conductors, such as metals; its kindling a Aame in combustible substances ; melting metals ; penetrating, splitting, and bruising bodies; killing animals; and ladly, iis influence on the magnetic needle. Our author confirms, farther, this important truth, by experiments made with a new apparatus of his own invention, which is very ingeniously contrived for the purpose. It is not possible to render this invention intelligible by description without the aflistance of the figures with which it is accompanied; but we can affirm, that the experiments made with it are fully satisfactory and decisive, though not new.
In the second part, Dr. Van MARUM hews how the lightning is produced by the natural clectricity of the atmosphere. Franklin, Beccaria, and others, who have made observations on the electrical force of the clouds in thunder-storms, tell us that some of these clouds have a positive and others a negative electricity. Two bodies, differently electrified, are known to attract each other; and as that, which is overcharged, or posi
For an account of the preceding volumes of the memoirs of this fociety, see the appendix to our 67th volume, p.511. 9
fively electrified, communicates its overplus to that which is undercharged or negatively electrified, it is natural to conclude, that different electrical states of the clouds in a thunder-storm give rise to this attraction and communication, and that the undercharged cloud receives an additional quantity of electric Kuid from that which is overcharged or positively electrified, But the thunder-clouds discharge the , electrical fiuid, on the earth, against eleyated bodies, such as houses, ftceples, and ships, This, however, says our author, is not to be considered merely as a communication of the electrical fluid to the surface of the earth, since it is proved by repeated experiments, that there can be no diffusion or discharge of the Auid of an electrified bodys unless that part of the body, to which it is communicated, has previously acquired an opposite force or power by the action of that famé electrified body near which, it is placed. So that before a thunder-cloud, positively electrifieds can diffuse its Auid upon any body; it must previously produce in that body, sub, jected to its action, a negative electricity; and vice versa, if the thunder-cloud be negatively electrified. This truth author proves by an experiment, in wbich be employs two plates, coated on one side: the one he suspends on a conductor, and insulates the other under it: the result is, that the electris cities and their effects differ, according as the second plate re: mains insulated, or is made to communicate with the earth by á chain or any other contrivance..
The third part of this dissertation contains an inquiry into the best methods of preserving our edifices, thips, and persons from the fatal effects of thunder-storms. Here M. Van MARUM naturally treats on conductors : he approves the pointed ones; evinces, by new experiments, that they are not dangerous, and thews that those with several points placed at considerable distances from each other, are more adapted to answer their purpose, than those which have only one. And here his expe. riments seem highly decisive, notwithstanding what is affirmed to the contrary in the third volume of the Memoirs of the Academy of Brusels, p. 11. 25. M. VAN MARUM difcufles the questions, that have been proposed relative to the height and thickness of conductors, the manner of compofing and placing them, the number that ought to be employed in an edifices with many other questions of this kind, which have been treated before him by able hands, to whose inventive labours he has added little or nothing, though he has placed them in a very useful light to the view of his countrynien.
In the fourth part of this dissertation the author describes the water-spout, the whirlwind, and the aurora borealis, meteors fufficiently known; and he inquires into their causes, which are, as yet, a subject of investigation and controversy. With APP, REY, Vol. LXVHI, SI
respect respect to the water spout, he adopts, as the moft probable, the opinion of the celebrated BECCARIA, who considers it as the effect of the electrical power of the atmosphere. The following reasons are alleged in support of this hypothefis. First, the spouts are, for the most part, formed during thunder-storms, and consequently, when the clouds are the most charged with electricity,-lightnings have been sometimes observed flashing with prodigious celerity about the water-spout,-attractions and repulfions of drops of water or other corpuscles, have been observed under the spout or the cloud whence it proceeded, which resembled electrical attractions and repulfions in a ftriking manner ;-and lastly, according to Beccaria, there are cbfervations which testify, that these meteors have been averted or diffolved by the elevation of pointed conductors, which are said, by the fame author, to be in general use among mariners, in those parts of the world where water-spouts are frequent. From these data M. VAN MARUM thinks, that some progress may be made in the theory of the formation of this meteor, though they may not furnish a perfe&t explication of its nature. The earth, Says he, must attract the electrical clouds that are at a small dia ftance from it; this attraction must necessarily exert ics 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 consequence, be accumulated in the lower part of the column, and as the weight of the column is thus continually increasing, it at length falls of a sudden by its own gravity. He observes farther, that if the water-spout be an electrical phænomenon, or the effect of electricity, the rising of the water under it, and the violence with which it carries up bodies from the surface of the earth, must be derived from the same 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 condensation is, into a tube, fomewhat like the fpiral screw of Archimedes, which absorbs and saises 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 dira sertation concerning contrary cleEtricities, publifhed at Roftock; and our Author adopts both the opinion and the arguments of that ingenious naturalist. He also looks upon it as highly probable, that the aurora borealis is nothing more than the electrical Auid, which diffuses itself in the higher and more rarefied parts of the atmosphere. On this head doctors differ, and some doctors of note, such as the ingenious and learned profeffor of Franeker, M. VAN SWINDEN, are not of our Author's opi. Hion. Great authorities, it is true, engaged M. VAN MARUM to seek the explication of the Aurora in the principles of electricity, and, for aught we know, it may be the true method: His reasons contain
nothing new : they are a summary of what Beccaria, Medier, Canton, Franklin, and Hamilton, have of fered on the subject.
The Second ARTICLE in this volume, is a differtation on dephlogisticated air, and the manner of obtaining it, and rendering it useful in respiration. By John IngenHỌUSZ, M. D. The ift part of this memoir contains general reflections on the salutary effe&s of dephlogisticated air in several diseases, occasioned or increased by breathing an air more or less corrupted by putrid ex. halations. The substances from which this air may be obtained, and its peculiar properties, when obrained 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 thewn an expeditious, cheap, and plain method of obtaining, during the summer- season, large quantities of dephlogisticated air, by means of the moft 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 last of these substances, is the most expeditious and the least expensive. But to obtain it in all its purity, and without any mixture of fixed air, care must be taken to Thake it in water, in order to walh 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 glass-receiver ; in which case, if the candle be re-lighted, and resumes a vivid Aame, it may be concluded with certainty, that all the fixed air has passed. It appears also, from the experiments here described (which Dr INGINHOUSZ made according to the method indicated in his Treatise on the property of vegetables to purify the air) that the first air which succeeds the fixed air is always the purest, and that the purity diminilhes in proportion as the operation draws near to its conclufion *.
The 3d part of this dissertation treats of the manner of obsaining dephlogisticated air from nitre. Our Author's method is in. genious, and by this time well known to the curious, as we suppose. The sth 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 passing through the lùngs Our Author does not approve of Fontana's method of using this air, because, by obliging the breather to stop his
Dr. Ingen housz gives, under this article, a curious and instructive table of the different degrees of puri:y, announced by his eudiometer, in the examination of dephlogisticated air, drawn not only frora aitre, but also from other substances, mineral and vegetable. SI 2
nostrils, noftrils, the acts of inspiration and exspiration are' rendered fa.' tiguing. After having, therefore, tried the experiment in different ways, he prefers the following: tåke two large bladder's, cleansed from their fat, and well dried ; rub them with fresh butter, or olive oil, that has no smell, to render them fofe 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 crd' ché rieck of a small bottle of caoutchouc, or elastic gun, at least three inches long, and as much in breadthi By several operations which our Author describes, and which may easily be conceiveit, this piece of elastic gum may be so fahioned, as to fit the note exactly, and to fit fo closely to the skiri, on all sides, as to preven't entirely the passage of the air. When all this is done, one of the bladders, filled with dcphlogisticated 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 posible care is used to keep the elastic refin so close about the nose, that the air may not be allowed to pass. If the bladder contains nearly 250 cubic inches of dephlogisticated air, of a good quality, it may be used in 16, perhaps 20 inspirations and exfpirations, hefore it be fu fardiminished 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 dephlogisticated air suffers by the action of the lungs. From thefe it appears, that the quantity of this air that is necessary to a single inspiration, does not become inferior in quality to common air, unul it has been four times exposed to the action of the lungs: the sth inspiration can add little alteration, since it is already overcharged with fixed air and phlogiston. How the dephlogisticated air, thus diminished in quality, may be restored to its former purity, by making it pass through water, and more especially through lime-water, our Author shews at great length; and the different proceffes he bas employed for this purpose, are here as accurately described as they are ingeniously contrived. But for an account of them we must refer the curious to the work itself.
M. INGENHOUSZ is of opinion, chat, to obtain any palpable advantage fiom this air in medical cases, 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 109 and 120 inspirations. In inflammatory, putrid, and other disorders, the dephlogisticated air may be sooner charged with phlogilton than in other cafes, and muft therefore be renewed more frequently. Our Author has found remarkable benefit from this air himself; afier taking a certain quantity of it, his cheerfulness, strength, and appet te, were increased, and his sleep was more calm and balmy chan usual..