Hour =2.265. But our author very justly remarks, that their computed distances fall very short of the real; and they seem to have counted too few steps to form their calculation on. Art. IX. On Infinite Series. By E. Waring, M.D.F.R.S.This article, as ufual, we fhall decline abridging.

Art. X. An Account of fome Appearances attending the Converfion of caft into malleable Iron. In a Letter from T. Beddoes, M.D. to Sir J. Banks, Bart. P. R. S.- Dr. Beddoes appears, from his reasoning on thefe appearances, to have abandoned the old, almoft forfaken, doctrine of Stahl *, and to have become an antiphlogiftian. It is impoffible to abridge the defcriptions, and of courfe the reafoning. The principal phænomena feem to be at a certain period of the process, the generation of an elastic fluid, and of a confiderable degree of heat.

Art. XI. On the Decompofition of fixed Air. By S. Tennant, Efq. F. R.S. -Our author's method of decompofing fixed air we fhall transcribe.

It has long been known, that when phofphoric acid is combined with calcareous earth, it cannot be decompofed by diftillation with charcoal for though vital air is more ftrongly attracted by charcoal than by phofphorus, yet in this compound it is retained by two attractions, by that which it has for phofphorus, and by that which the phosphoric acid has for lime; fince the vital air cannot be difengaged unless both thefe attractions are overcome. As these attractions are more powerful than that which charcoal has for vital air, if phofphorus is applied to fixed air and calcareous earth, the vital air will unite with the phofphorus, and the charcoal will be obtained pure. Thefe fubftances, in order to act upon each other, must be brought into contact when red-hot; and this may be eafily affected in the following manner. Into a glafs tube, clofed at one end, and coated with fand and clay to prevent the fudden action of the heat, a little phofphorus fhould be first introduced, and afterwards fome powdered marble. The expe riment fucceeds more readily if the marble is flightly calcined, probably becaufe that part which is reduced to lime, by immedi ately uniting with the phofphorus, detains it to act upon the fixed air in the other part. After the ingredients are introduced, the tube fhould be nearly, but not entirely clofed up: by which means fo free a circulation of air as might inflame the phofphorus is preyented, whilft the heated air within the tube is fuffered to escape. When the tube has remained red-hot for fome minutes, it may be

We perceive, in a late periodical work, the New London Medical Jourhal, of which we purpose to give fume account, that Dr. Black has joined the band of apoftates.

CRIT. REV. N. AR. (IV.) March, 1791.

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taken from the fire, and must be fuffered to grow cold before it is broken. It will be found to contain a black powder, confifting of charcoal intermixed with a compound of lime and phosphoric acid, and of lime united with phofphorus. The lime and phof phoric acid may be feparated by folution in an acid and by filtration, and the phosphorus by fublimation.'

The coal thus produced did not differ from the charcoal of vegetables. This double power of attraction did not change either the marine or the fluor acid.

Art. XII. Meteorological Journal, principally relating to Atmospheric Electricity; kept at Knightsbridge, from the 9th of May 1789, to the 8th of May 1790. By Mr. J. ReadThe journal is of the highest importance, though incapable of abridgment. The meteorological phænomena are little underftood, probably because we have not fufficiently attended to atmospheric electricity. At the fame time, it must be obvi ous, that more than one journal should be kept to render the obfervations applicable. Three fhould undoubtedly be kept on the different feas that furround the island, to examine the connection of the atmospheric electricity with the tides: perhaps as many in the inland parts, and fome in the neighbourhood of higher mountains. Our author's apparatus deferves

imitation.

Art. XIII. Farther Experiments relating to the Decompofition of dephlogisticated and inflammable Air. By J. Prieftley, LL. D. F.R.S.-Dr. Prieftley hangs with the eagerness of apprehenfion on his old opinions; but his candour, in carefully examining the different facts, and confeffing his errors, is highly fingular and commendable. He finds that the acid is not really owing to the azote, but to the proportion of the pure and inflammable airs inflamed in the production. If the former is in excefs, the acid appears. When there is not enough of the latter, the phlogisticated air is decompofed; when too much, fome is even produced. There is fill, however, reafon to fuppofe that the phlogisticated air is in fome measure connected with the acid, from the circumftances in the first of the following paragraphs; and we fhall copy the other, not only on account of the information which it contains, but to fhow how unwilling Dr. Prieftley is to resign his former opinions.

When I first prepared an account of my late experiments for the Royal Society, I entertained this idea; but I now confider it as a leaft uncertain, because when I mix the two kinds of air in fuch proportions as to produce water, I find in the refiduum much more phlogifticated air than I do when acid is produced, which af

fords

fords a fufpicion that, in this cafe, the principle of acidity goes wholly into the phlogisticated air, which, as my former experi ments fhew, actually contains it, though it is not easy to ascertain in what proportion.

Having exploded three ounce meafures of a mixture of fomething more than two parts inflammable air, and one of dephlogifticated, and another equal quantity in which the inflammable air bore a lefs proportion to the dephlogisticated, the former of which I knew would yield water, and the latter acid, I found the refiduum of the former to be 0.57 oz. m. not affected by nitrous air, and weakly inflammable; and in order to find how much phlogifticated air it contained, I mixed different proportions of phlogifticated and inflammable air, and concluded from the manner of firing them, and this refiduum, that it could not confift of less than one third of phlogisticated air, viz. o.19 oz. m. But the residuum of the mixture which would have produced acid was 0.62. oz. m. of the ftandard of 110, which I find by computation to contain not omre than 0.062 oz. m. of phlogisticated air. I repeated this experiment very many times, and never failed to have a fimilar refult; fo that it is very poffible that the pure-water we find may be nothing more than the bafis of the two kinds of air; and the principle of acidity in the dephlogiftated air, and the phlogiston in the inflammable air, may combine to form a fuperfluous acid in the one cafe, and the phlogisticated air in the other.

This fuppofition is ftrengthened by finding that whether the produce be acid, or pure water, the two kinds of air unite in nearly the fame proportions. But fince water has an affinity to almost every fubflance in nature, and a peculiarly ftrong one to the acid and alkaline principles, it may be impoffible that it fhould be wholly free from them; and if they be in proper proportions to faturate one another, and in the fame quantities, their prefence may never appear.'

Thus are we approaching nearer to the confirmation of the opinion refpecting the compofition of water, and ftill nearer to the downfall of the phlogistic system. It is held up almost by Dr. Priestley alone.

Art. XIV. Experiments on Human Calculi. In a Letter from Mr. T. Lane, F. R. S. to W. Pitcairn, M. D. F. R. S. -The fubftance of thefe experiments have been long before the public, and the detail is of little importance. They only fhow that calculi differ in their chemical qualities; and that volatility is connected with folubility in alkalis. Do these remarks, however, at all influence the doctrine of a peculiar acid? Why is our very able (unknown) correfpondent the author of the Treatise on the Stone and Gravel,' fo long filent?

Art. XV. Chermes Lacca. By W. Roxburgh, M. D. of Samulcotta.

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Samulcotta. Communicated by P. Ruffel, M. D. F. R.S.Dr. Roxburgh defcribes thefe little animals very carefullyThe number of males is not more in proportion to that of females than as one to gooo. The eggs, and glutinous liquor they are found in, is of a bright red colour; and our author thinks, if carefully preferved, would be as valuable as cochineal.

Art. XVI. The Longitudes of Dunkirk and Paris from Greenwich, deduced from the Triangular Measurement 1787, 1788, fuppofing the Earth to be an Elipfoid. By Mr. J. Dalby; communicated by C. Blagden, M. D. Sec. R. S.-The longitude of Dunkirk refpecting Greenwich has been hitherto computed by fpherics, fuppofing that the furface of a sphere nearly coincides with the furface of the earth from eaft to weft On an elipfoid it is about 1.5 more; on a more accurate calculation it fcarcely, perhaps, reaches 1".

Art. XVII. On the Method of determining, from the real Probabilities of Life, the Values of contingent Reverfions in which three Lives are involved in the Survivorship. By Mr. W. Morgan, F. R. S.-This is a very correct and valuable article; but it is impoffible to abridge it. The calculations are accurate, and the method clear and ingenious..

Art. XVIII. Abstract of a Register of the Barometer, Thermometer, and Rain, at Lyndon in Rutland; by T. Barker, Efq. with the Rain in Surrey and Hampfhire, for the Year 1790. Communicated by T. White, Efq. F. R.S-The thermometer was from 85 to 251: but the former number was evidently from reflected fun, fince the thermometer within doors was never above 75 in the fame month. The barometer was from 30.13 to 28.32. The rain at Lyndon 21.629 inches; at South Lambeth, 22.31; at Selbourn 32.27; at Fy field 22.05. The winter was mild; the fummer cold and fhowery; the autumn warm.-Mr. Barker adds an account of chalk found at Redlington in Rutland, and at Stukeley in Huntingdon, out of the ufual direction of the chalk beds.-But that these have the fixed direction which he fuppofes, we fufpect to be without foundation.

Art. XIX. Defcription of a fimple Micrometer for measuring fmall Angles with the Telescope. By Mr. T. Cavallo, F.R.S.

The micrometer confifts of a piece of mother of pearl, minutely divided, and fituated in the focus of the eye-glafs of a telescope. It is eafily conftructed; and its ufe, by means of the table fubjoined, will be found very convenient.

Art. XX. A new Method of Inveftigating the Sums of Infinite Series. By the Rev. S. Vince, A. M. F. R. S.-An ingenious paper, incapable of being given in an abstract.

Art

Art. XXI. Experiments and Obfervations to investigate the Compofition of James's Powders. By G. Pearfon, M. D. F.R.S.-We have feen nothing more clear and fatisfactory than the investigation before us. The peculiar preparation of antimony, fold as Dr. James' invention, is a very convenient and useful one. Our author firft examines this preparation with that minute and scientific chemical acumen, that scarcely leaves room for doubt or fufpicion: nothing of the flightest practical importance feems to have remained without investigation. From 240 grains, he procured 100 of phofphorated lime; 57.15 of algaroth powder, a foluble calx of antimony; 19.85 of an infoluble antimonial calx, with a little phosphorated lime; 55 of the fame calx, with a fufpicion only of the mixture of lime. The deficiency amounted but to 8 grains. The following facts are curious and little known.

The above analyfis fhewed no effential ingredients of James's powder but antimonial calces, phosphoric acid, and calcareous earth, which two laft fubftances appeared to be united together; but it would have been vain and unneceffary labour to have attempted to make this powder by mixtures of any of the commonly known calces of antimony and phofphorated time; because none of them, from their well known qualities, could form a powder of the fame colour and specific gravity as James's powder, and like it partially foluble in acids. From the above experiments, however, the probability was evident, that this fubftance might be made by calcining together antimony and bone-afhes; which operation produces a powder called Lile's and Schawanberg's feverpowder; a preparation defcribed by Schroder and other chemists 150 years ago. The receipts for this preparation differed in the proportion of the antimony to the bone-afhes, and in the state of the bone; fome directing bone-fhavings to be previously boiled in water; others ordered them to be burnt to afhes before calcining them with antimony; and in other prescriptions the bone-shavings were directed to be burnt with the antimony. According to the receipt in the poffeffion of Mr. Bromfield, by which this powder was prepared forty-five years ago, and before any medicine was known by the name of James's powder, two pounds of hart's-horn fhavings must be boiled to diffolve all the mucilage, and then, being dried, be calcined with one pound of crude antimony, till the fmell of fulphur ceafes, and a light grey powder is produced. The fame prefcription was given to Mr. Willis, about forty years ago, by Dr. John Eaton, of the college of phyficians, with the material addition, however, of ordering the calcined mixture to be exposed to a great heat in a clofe veffel to render it white. Mr. Turner made this powder above thirty years ago by calcining together equal weights of burnt hart's-horn and antimony in an open

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veffel