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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 pass 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 see, 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 otherwife, in the fame manner, and still found that the down remained electrified. 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 ftill 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 up wards 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 because 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 attracted by electrified wax, &c. and thofe 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 smoke and steams must be either electrics, or non-electrics electrified, it was eafy to fuppofe them non-electrics, as they arife from nonelectric

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electric bodies; and the more, because the higheft 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 glafs 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 pafled 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 electrified 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-électric not electrified.'

Art. 27. The Abbè Sauvages, of the Royal Society of Montpelier having difcovered, 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 folio finuato pubefcente, T. 611. which is a native of Virginia, ftruck a finer and fpeedier 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 leaft 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 wafhings, 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 ftain all their utenfils, and that the Calicuts paint themselves, with it.-This varnish is obtained by wounding the tree (a). It is white, and clammy, at first, but foon turns black when expofed to the air; and needs no preparation, unless fome dirt fhould 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 fkin 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 poifon-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 those who handle it, unless they tie a handkerchief over their nofe and mouth.

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 themay not only felves, 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's 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 whole baptifm's no account is taken, Dr. Brackenridge justly observes, fenders the London bills of mortality very incompetent regifters of births: he alfo takes notice that, in computing the probability of life, there is no better dependence on the num bers 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 state. Hence he concludes, that thofe who have formed their calcu lations upon the London bills only, have been led into feveral mistakes and inconfiftencies.

Dr. Halley, whofe table has ever been efteemed the most exact, and ufeful, of any thing of this kind, founded his computations on the bills of mortality at Breflau; but the difference 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 propofes to rectify the errors that have arifen from the feparate confideration of thefe bills, by making use of ours, fo far as the age of twenty years, and those of Breslau for the fubfequent periods of life.

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 cafily 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 263. 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 baptifins known, 14626, taken likewife at a me

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 refpective periods at Breflau. From this table thefe nombers are taken.

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dium, for the fame ten years, from 1743 to 1753 inclufive, by the number 4935.

From which, by the way, we may fee, as this difference between the births and baptifms must be occafioned by diffenters, that the number of fuch, of all denominations, both proteftant, and popifh, with the Jews, do not make above one fourth of the whole of the people within the bills of mortality; and confequently that the proteftant diffenters, exclufive of Quakers and Jews, are not above an eighth. part of the whole. And we may alfo obferve, that as the difference between the births, 19561, and burials, 24867, is 5306, there must be a conftant fupply, yearly, of at least 5000 ftrangers, to keep up the people within the bills, to their prefent number: and the births are to the dead, yearly, about four to five.

Now, from the births found, 19561, and the numbers of the dead in the different periods known by our bills, it will be easy to form a table of the decrements of life; because the dead in the intermediate years may be found by what has been faid above. And accordingly I have computed the following, which is conftructed from the London and Breflau bills together; which I think is a furer method of computing for us at London, than from either of them alone. The first part, to the 21ft year, is done from our bills, and the other part from the Breflau; but it is formed in such a manner, that it goes on, as if from the bills of one place only. For after the age of twenty it is continued by proportion, by making the dead at London in the decennial periods, to have the fame ratio to one another, as the dead at Breflau. It fuppofes one thoufand perfons born in one year, and fhews the annual decrease of them by death till eighty-feven years of age, which may be confidered as the utmost period of life. The intermediate numbers marked d, fhew the dead in each year. The ufe of this table is well known to all who can compute the value of annuities for lives.

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Age Perf.:

16 386

3 d.

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127 d.

17. 383

9 d.

3 550 45 d.

4 d.

8

.4 d.

425

7 d.

13 398
4 d.

4

505 3.2 d.

9 418

14 394

6 d.

4 d.

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18 379 ..4.d.

19 375

3 d.

372
4 d.

Age

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