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It is evident, that, upon electrifying any light matter, • fuch as down, or the downy parts of feathers, their fpeci<fic gravity is much leffened; and that by holding another • electrified body under them, they may be driven upwards at pleasure. It is alfo evident, from experiment, that the. more you divide the parts of fuch bodies, the more of their fpecific gravity they will lofe by being electrified; and by. dividing them into very minute parts, I have found, that they afcended to a confiderable height after they were electrified. From whence I think it highly probable, that the • exceeding fmall particles of vapour and exhalation may be, and are fufficiently electrified to render them fpecifically lighter than the lower air; and that they do afcend by that means. And that they will afcend proportionably higher, as the furrounding fluid is proportionally greater than the • particle which is carried up.'

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Our Author next proceeds to fhew, that the afcent and defcent of vapour and exhalatioh, attended by this electrieal fire or fluid, is the caufe of all the regular and irregular motions we find in the atmofphere. And alfo, First, why it generally rains in winter while the wind is fouth, fouth-weft, and wefterly. Secondly, why north-weft winds. are generally attended by fhowers in the beginning, and be-come more dry as they are of longer continuance. Thirdly, ⚫ why north and north-eaft winds are generally dry. Fourthly, why the caft wind continues dry and dark for a confi<derable time together. Fifthly, why fqualls precede heavy and diftinct fhowers; and why a calm enfues for fome little. time after they are paffed. Sixthly, why forms and high, winds feldom happen in a ferene fky, without clouds. Seventhly, why the vapours, in warm feafons, coalefce to form thofe diftinct denfe clouds, which produce thunder and heavy fhowers. Eighthly, why the barometer falls loweft in • long continued rains, attended by winds; and why it rifes highest in long continued fair weather; and why the inter• mediate changes happen. Ninthly, of land-breezes, and fea-breezes, and water-fpouts."

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It would extend this article too far, to fhew in what manner Mr. Eeles has accounted for thefe phænomena; we fhall therefore only add the experiments by which our Author found all afcending vapours and exhalations to be electrified..

I extended,' fays he, a fine ftring of filk eight feet horizontally, and from the middle fufpended two pieces of fuch down as grows upon our turf-bogs, by two pieces of fine. filk, about twelve inches each in length; and then, by rub-.

bing a piece of fealing-wax on my waistcoat, over my fide, I • electrified the pieces of down; and then brought fundry burning things under them, fo as to let the fmoke pafs in great plenty thro' and about them, to try whether the electric fluid would run off with the fmoke; but I had the pleasure to fee, that the down was but a little affected by the paffage of the fmoke, and ftill remained electrified. I then brought fundry fteams from the fpout of a boiling tea-kettle, and other wife, in the fame manner, and ftill found that the down remained elec trified. I then breathed on them in great plenty, but found that the down ftill remained electrified. I then joined the palms of my hands together, with the fingers extended perpendicularly under the down, which still remained electrified, • altho' the fubtile effluvia, thrown off by perfpiration, paffed in great plenty through the down; as may appear by holding one or both the hands in the fame manner, under any light matter floating in the air, which will be driven upwards thereby, with as great velocity as an electrified feather is, by any electrified body held under it. In short, I tried all the vapours and exhalations I could think of, in the fame ⚫ manner, and with the fame fuccefs.

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I then warmed a wine-glafs, and with the fkirt of my coat held infide and outfide, the glafs between my fingers and thumb: I rubbed the glafs brifkly about, and electrified the down, and found all experiments anfwer in the fame manner as they did with the wax. I mention this particular becaufe fome writers on electricity have faid, that there were two kinds of electrical fire, the one refinous, and the other Vitreous; becaufe light bodies, electrified by glafs, are at⚫tracted by electrified wax, &c. and those electrified by refins are attracted by glass. But I think thefe different effects muft arife from fome differing qualities in the refin and glass, which have power to actuate this fire differently. For if there were really two diftinct fpecies of this fire, oppofite in <their nature, the aforementioned experiments would have a very different confequence from what appears. For if the vapours were impregnated by the vitreous fire, they must abforb, or fome way difturb the refinous fire, which electrifies the down, and fo vice verfa: but we find, that the ⚫ fame vapour, with its electric fire, paffes through the electrified down, in the fame manner, whether it be electrified by glafs or refin.

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The electricity remaining in the electrified down, after thefe experiments made it appear, that the fmoke and steams must be either electrics, or non-electrics electrified, it was eafy to fuppofe them non-electrics, as they arife from non

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• electric bodies; and the more, because the highest electrics, by a difcontinuity and comminution of their parts (long be*fore they come to be as minute as the particles of afcending vapour) become non-electrics, or conductors of electricity. For glafs, refin, wax, &c. all become non-electric, even in fufion. But to try whether the fteams, &c. were nonelectrics, I only bedewed the wax and glass with my breath, fteams, &c. from my hand, to the end of the wax and glafs; and then touching the electrified down with the end of the glafs or wax, I found that the electrical fire immediately paffed from the down into my hand, through the fteams, &c. which refted on the wax and glass. Which I think fufficiently proves the fteams, &c. to be non-electric; ⚫ and I think, that it as plainly appears, that they are all elec• trified while afcending, because the electrical fire in the down does not join with them in their paffage through it; which otherwise it would do with them, or any non-electric not • electrified.'

Art. 27. The Abbè Sauvages, of the Royal Society of Montpelier having discovered, that the juice of the Toxicodendron Carolinianum foliis pinnatis, floribus minimis herbaceis tinged linen with a deeper black than any other known preparation, and without the leaft acrimony; the Abbè Mazeas, F. R. S. informs Dr. Hales, that it indeed is an excellent black, but that the juice of the Toxicodendron triphyllum folie finuato pubefcente, T. 611. which is a native of Virginia, ftruck a finer and speedier black than the former, which however was exceeded by the juice of the Toxicodendron triphyllum glabrum, T. 611. Neither boiling water with foap, nor a ftrong lye of the afhes of green wood, diminished in the least the depth and fplendor of these colours.

As the blacks of our painted cloths, prepared from iron and nut-galls, grow rufty after a certain number of washings, and in time wear out, this American, and more lafting, varnish, may be an improvement. Mr. Philip Miller, however, informs the fociety, that it is no difcovery of the Abbè's, as Kæmpfer mentions the black-tinging quality of the Carolina Toxicodendron; and we know, that the Japanese stain all their utenfils, and that the Calicuts paint themfelves, with it.This varnish is obtained by wounding the tree (a). It is white, and clammy, at first, but foon turns black when exposed to the air; and needs no preparation, unless fome dirt should mix with it, and

(a) When the fhrub is fufficiently drained of its juices, they cut it down to the ground: New ftems arife from the root, which in three years are again fit for wounding.

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then the Japanese ftrain it through a coarfe gaufe, and putting it into wooden veffels, doubly fecure it from evaporating, with oil, and a skin over it. A good varnith is alfo made of the juice of the Cafhew-nut-tree.

The firft fpecies, the inhabitants of Carolina, and the Bahama iflands, call poifon-tree, and poison-afh; and the other two forts are named poifon-oak, in Virginia and New England. Thefe appellations are expreffive of their properties; for the varnish emits a poifonous vapour, which occafions violent head-achs, and fwellings of the lips, of thofe who handle it, unless they tie a handkerchief over their nose and mouth.

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As the Toxicodendrons are common in our northern, and the Cafhew-nut-trees in our fouthern colonies of America, it were to be wifhed, concludes Mr. Miller, that the inhabitants of both would make fome experiments to collect this varnish, as it may not only produce much profit to themfelves, but also become a national advantage.

Art. 28. A Letter to the Right Hon. the Earl of Macclesfield Prefident of the Royal Society, concerning the method of conftructing a table for the Probabilities of Life, at London; from the Rev. William Brackenridge, D. D. and F. R. S.

The generally affumed data, employed by political arith-" meticians in their calculations, have, when feparately taken, been often found uncertain, and fometimes manifeftly erroneous; nevertheless, that, in conjunction, there is more than a probability of making fome ufeful deductions from them, this article pretty clearly evinces. The number of diffenters, of various denominations, as well foreigners as natives, of whofe baptifms no account is taken, Dr. Brackenridge juftly obferves, renders the London bills of mortality very incompetent regifters of births: he also takes notice that, in computing the probability of life, there is no better dependence on the numbers of burials therein delivered, efpecially above the age of twenty; as about that period there is a continual acceffion of multitudes of ftrangers to this metropolis, on different occafions: whereby our burials are always in a fluctuating ftate. Hence he concludes, that those who have formed their calcu lations upon the London bills only, have been led into feveral miftakes and inconfiftencies.

Dr. Halley, whofe table has ever been efteemed the most exact, and useful, of any thing of this kind, founded his com putations on the bills of mortality at Breflau; but the differ ence of country, and way of living, having been objected REVIEW, Oct. 1756.*

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against Dr. Halley's fcheme, with refpect to London, Dr. Brackenridge proposes to rectify the errors that have arifen from the feparate confideration of these bills, by making use of ours, fo far as the age of twenty years, and those of Breslau for the fubfequent periods of life.

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Upon this principle our learned calculator endeavours to determine the annual number of births here; in order to which, fays he, we must have the number of burials known, at least in the feveral periods, till the 20th year; viz. under two, • between two and five, between five and ten, and between ten and twenty. And it is evident, if we fuppofe no acceffion of ftrangers, that the number of the living, in any one year, will be equal to the difference between the births and ⚫ the fum of all the fubfequent burials at each age till that year. The number of the living in any one year is eafily known, if we fuppofe the probability of life to be the fame as at Breflau; for then the number of dead there, will be to the number of the living, as the dead at London to the living. • Thus in the 20th year, the dead and living at Breslau are as 6 and 598, and the dead at London are 73, or more exactly 72,88; therefore the living must be 7263. The dead in the intermediate years at London may likewife be found, by means of Dr. Halley's table. For, by proportion, if the dead at Breflau, from the age of ten to twenty complete, be 61, and in the 20th year 6, and the dead at London for the fame period be 741; then will the dead in the 20th year be 73. And therefore if the living at London, in the 20th year of their age be found to be 7263; this must be equal to the number of births, having substracted from them all the dead in each of the preceding nineteen years. And confequently, if we put for the number of births, we fhall have this fimple equation: x-8819-2006-805-741 * +73= 7263; and thence the number of births X=19561. And ⚫ the fame number would have been produced from any inter• mediate age, between twelve and twenty. So that, if we could be certain of the number of the dead, there could be no doubt, but that 19561, would nearly, at an average for ten years, be the whole of the births yearly. And this is greater than the ⚫ number of baptifms known, 14626, taken likewife at a me

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Dr. Brackenridge has, in the beginning of the article, given a table of the number of burials, at the feveral ages, taken upon an average, from the bills of mortality, for ten years, from 1743 to 1753 to which he has annexed the numbers of the dead at the respective periods at Biellau. From this table these numbers are taken.

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