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tions of air were found to be as nearly as poffible of the fame dimenfions, and of the fame degree of purity.'

From these and other experiments the Author at first concluded, that mice would not live in dephlogifticated air till they had completely phlogifticated it, which happens when they die in common air; though they lived longer in the former than might be expected from its purity, as indicated by the nitrous teft. He neglected then, however, to put other mice into the remaining dephlogifticated air. Attending to this circumftance afterwards, he found that when the fecond moufe died in this remaining air, it was as completely phlogisticated, as common air is generally found to be, when mice have died in it; and that the death of the firft mouse, long before the complete phlogiftication of the air, was principally occafioned by its long continuance in the cold, after having paffed through water.

In a fubfequent fection the Author fatisfactorily fhews the fallacy of the new method of afcertaining the purity of common air by means of nitrous air, propofed by the Abbé Fontana, and defcribed by Dr. Ingenhoufz in the work above referred to *. From the Author's experiments and reafonings, it appears, that philofophers ought to be as attentive as ever to the strength of the nitrous air, employed as a teft of the purity of common

air.

Many new obfervations follow refpecting that peculiar modification of nitrous air, formerly discovered by the Author, which he is now induced to call dephlogisticated nitrous air; and which poffeffes the peculiar properties of admitting a candle to burn in it, though it still continues as fatal to animal life as any of the moft noxious fpecies of air; and fometimes will diminish common air as much as fresh made nitrous air, though at other times it is not poffeffed of this power. The Author has now found an eafy method of producing this fingular species of air in great abundance, merely by putting iron into a folution of copper in nitrous acid.

Some curious and fingular experiments are next related, in which the Author treats more particularly than he had before done, of the production of a genuine inflammable air; merely in confequence of repeatedly tranfmitting electric fparks, or explo❤ fions, through a given quantity of alcaline air confined by quickfilver. He carried on this procefs, as he fuppofed, to its maxinum; or till he judged that the electric explosions made no addition to the bulk of the air: and he found that the space finally Occupied by the air was, as nearly as poffible, three times as great as that which the alcaline air alone had originally occupied.

See the fame volume of our Review, pag. 349.
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This

This air exploded in the fame manner, and appeared in every other respect to be of the fame nature as that procured from iron or zinc, by means of the vitriolic or marine acids. And though water was admitted to it, and frequently agitated with it, during two whole days; no fenfible part of it was abforbed, nor had the water acquired a fmell of volatile alcali. When, however, this air was made to explode, the Author, on inftantly applying his noftrils to the mouth of the veffel, perceived a very evident alcaline fmell: from which he infers, that the whole of the volatile alcali had not been completely incorporated with this air; though the combination was iufficiently intimate, to deprive the volatile alcali of its property of being abforbed by water.

This curious experiment undoubtedly deferves to be repeated on a larger fcale, and the process to be carried on, till the ope rator be perfectly affured that no additional explosions will produce any further effect on the alcaline air. The water afterwards added to it fhould likewife be ftrictly examined. There appears here to be either an actual decompofition of the volatile alcali; or a new combination formed of it with some additional fublance. The questions, accordingly, that naturally occur here are-Is its own abundant phlogifton only feparated from the alcaline air, by the electric explotions, fo as to constitute inflammable air; and in that cafe, what becomes of its other principle or principles?-or does the electric matter conduct, from other fubftances, or itfelf furnish, more phlogifton, to the alcaline air; fo as to conftitute a kind of neutral compound, infoluble in water?-or laftly, is there, in this cafe, a difunion of principles, and an increafe of dimenfion, effected merely by the intense heat of the electric explofions; as is hinted at pag. 385-We ought to have premifed a conjecture of the Author's

that inflammable air in general confifts of phlogifton combined with fome basis, which is of an alcaline nature; and that the phlogifton of this inflammable air is principally fupplied by the electric matter.

The next fection contains an account of fome fingular experiments, thewing the remarkable volatility of that ponderous metallic fubítance, quickfilver, under certain circumstances. The evaporation of mercury in vacuo, or rather its fubfequent condenfation into globules, in the upper part of a barometer, had been before oblerved. The Author too had formerly taken notice of a black matter lining the cavity of the upper part of a glits fyphon, containing vitriolic acid air confined by mercury, when he tent decric explosions through it: but at that time he entertained no fufpicion that this matter came from the quickfilver; imagining that it was altogether formed from the vitrilic acid air.

Without

Without mentioning his previous experiments relative to this fubject, we fhall only obferve, that he made the electrical explosions, in vitriolic acid air, not from the furface of the mercury itfelf, but between two wires, placed at the great diftance of three feet above it; and he found that the black matter was, to all appearance, produced quite as readily, as when the explofions had been taken ever fo near to the furface of the mercury. As this black matter on applying heat to it, was found to be mercury; it feems that the mercurial vapour must have completely and previously pervaded the whole fpace, filled with vi triolic acid air; and that the electric matter found it already difperfed throughout this air, and did not produce any proper evaporation, or mechanical trufion, of the mercury, by its immediate action upon that fluid. It even appears, from other experiments of the Author's, that mercury exifts in the form of vapour, in common air: for here too the black matter is produced, though not fo plentifully, and only at a finall diftance above the furface of the mercury.

To thefe experiments fucceed others-on the nitrous acid exifting in metallic calces;-on the extraordinary volatility given to the nitrous acid, on its admixture with the vitriolic, from which it entirely efcapes;-and on the marine acid, dephlogisti cated by means of manganefe: a difcovery, we believe, of Mr. Scheele's, The experiments made with the acid in this new state (in which it will, fingly, diffolve gold) confirm the opinion which the Author had always entertained; that a certain portion of phlogifton is neceffary to all fubftances, and especially acids, affuming the form of air.' The marine acid, thus de-, prived of phlogifton, is actually brought into a state very nearly refembling that of the nitrous acid; being now, like it, incapable of affuming the form of a permanent air, that is, of an air that can be confined by quickfilver; which fubftance it immediately corrodes, forming probably with it a kind of corrofive fublimate. Mr. Watt, in a subsequent note, properly obferves that this is perhaps an eafier, as it certainly is a more direct, way of making that preparation, than the common process.

In the following fections are contained-Obfervations on the lateral electrical explofion, formerly printed in the Philofophical Tranfactions; and fome mifcellaneous experiments in electricity. These are fucceeded by others relative to found, in different kinds of air; and by a few experiments of a miscellaneous

nature.

Towards the end of this volume, the Author has added a methodical Index, or a fummary view of all the more important facts contained in this and the four preceding volumes, under diftinct heads; with references to thofe parts of the work in which they are more largely treated of. This recapitulation

will be found to be exceedingly useful and instructive. A fection is added too, containing explanations or corrections of various paffages in the four former volumes; fuggefted by fublequent experiments or obfervations. An Appendix to this volume contains-An Extract of a Letter from Mr. Arden, defcribing a very fingular appearance produced by artificial electricity;-some obfervations on different parts of this volume, by Mr. Watt, and Mr. Bewly ;-a defcription, accompanied with a drawing, of a new apparatus for impregnating water with fixed air, invented by Dr. Withering;-and an account, by Mr. Warltire, of a very curious experiment made by him; from which it seems to follow, that the latent heat in bodies adds to their weight, or that fire is actually beavy. At least, the fact is, that on firing inflammable air, by the electric fpark, in a copper flask holding three pints, perfectly clofed, and accurately weighed before the explofion; it was found, after the explosion, that the veffel weighed less (generally two grains) than before.

We fhall only add our wifhes, that the Author, now entering,' as he obferves, on a new period of life,' (at Birmingham) may have it in his power to realife the hopes, which he expreffes in his Preface, that, in his new fituation, he fhall be enabled to devote himself, as much as in any former period of his life, to philofophical purfuits.' In thefe wishes every friend to philofophy will, we doubt not, heartily concur with us.

B...y.

ART. IV. A Regifler of the Going of Mr. Mudge's firft Time-keeper, from April 18th, 1780, to May 7th, 1781: with two other Regifters of the fame Time-keeper. 4to. A S. Cadell. 1781.

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N our Review for September laft, we gave a very particular account of a watch of Mr. Arnold's making. Juftice to both artists requires, from the Reviewer, as particular an account of the going of this Time-keeper.

The publication before us contains, as the title expreffes, three feveral regifters of the going of the fame watch, at three (fomewhat diftant) periods of time.

The firft in point of time, though not placed fo in the pamphlet, was kept by the Rev. Profeffor Hornsby at Oxford, from June 20th to October 31ft. The year is not mentioned; but there are some reasons for fuppofing it was in 1776. In this trial, the greateft difference between the rates of the watch, on any two days in that time, was 4"35; namely between its rate. on July 4th, when it loft 257, and its rate on July 30th, when it gained 178. The difference between its rate on any one day and the next day to it, was 3"76; namely between July 30th, on which day it gained 178, and July the gift,

"

when

when it loft 1"98. In this time Fahrenheit's thermometer was never higher than 68, nor lower than 48.

"

When the watch was carried down to Oxford, in June, it gave the difference of longitude between that place and Greenwich 53 in time. When it was brought up from thence, the 1ft of November following, it made the difference of longitude between thofe two places 5' 1" 8 the mean of the two is 52"; and the true longitude of Oxford, as determined by aftronomical obfervations, is 5' 2" W.

It was next tried at Greenwich, under the infpection of the Rev. Dr. Mafkelyne, Aftronomer Royal, from November the 12th 1776, to November the 30th 1777. The watch appears under rather lefs favourable circumftances in this trial than it did in the laft; but its going here was by no means bad. For the first month, or more, its rate of going was very near mean time; but towards the latter end of February it began to acceJerate, and before the end of March gained rather more than 5" on a day but at the end of this month it fell off again to 3 conds and a fraction, and continued to go at that rate, with most amazing regularity until the latter end of September, when it began to accelerate again, and was gaining 5" nearly when the journal is closed.

fe

The greatest difference between its rates on any two days in these thirteen months was 72; namely, between its rates on January theft, on which day it loft 1" 46, and November the 30th, when it gained 5" 74. The greateft difference between its rates of going on any one day and the next following is 3" 06; namely, between its rate of going on January the 9th and its rate on January the roth. The greatest height of the thermometer during this trial was 70, and the least 26 degrees.

After this trial, we are told, that Mr. Mudge endeavoured to difcover and remove the cause of the irregularities which were obferved in the watch's going; and the fuccefs of his endea vours will be beft feen from the following account of the laft of the three trials which are here given.

It is to be observed, that the account before us is totally filent as to the place where, as well as the perfon by whom this laft trial was made *. It must also be acknowledged, that the comparer laboured under another difadvantage, in not being able to regulate his clock by aftronomical observations, but to be obliged to fetch the time from Dr. Heberden's clock, by means of watches.

On these two accounts, the authority of this trial may want weight with fome perfons, who will not be able to object to the

• We are told it was by Count Brubl.

two

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