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tions of air were found to be as nearly as possible of the same di. mensions, and of the fame degree of purity.'

From these and other experiments the Author at first concluded, that mice would not live in dephlogisticated air till they had completely phlogisticated 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 teit. He neglected then, however, to put other mice into the remaining dephlogisticated air. Attending to this circumstance afterwards, he found that when the second mouse 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 first mouse, long before the complete phlogistication of the air, was principally occasioned by its long continuance in the cold, after having passed through water.

In a subsequent section the Author satisfactorily thews the fal. lacy of the new method of ascertaining the purity of common air by means of nitrous air, proposed by the Abbé Fontana, and described by Dr. Ingenhoulz in the work ahove referred to *. From the Author's experiments and reasonings, it appears, that philosopbers 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 observations follow respecting that peculiar modi. fication of nitrous air, formerly discovered by the Author, which he is now induced to call dephlogisticated nitrous air ; and which possesses the peculiar properties of admitting a candle to burn in it, though it still continues as fatal to animal life as any of the most noxious species of air ; and sometimes will diminish common air as much as fresh made nitrous air, though at ocher times it is no: pofleffed of this power. The Author has now found an easy method of producing this singular species of air in great abundance, merely by putting iron into a solution 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 infiammable air; merely in consequence of repeatedly transmitting electric sparks, or explofions, through a given quantity of alcaline air confined by quickfilver. He carried on this process, as he supposed, to its maxi. mum; 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 possible, three times as great as that which the alcaline air alone had originally occupied.

See the same volume of our Review, pag. 349.

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This

This air exploded in the same manner, and appeared in every other respect to be of the same nature as that procured from iron or zinc, by means of ihe vitriolic or marine acids. And though wat's was admitted to it, and frequently agitated with it, during two whole days; no sentible part of it was absorbed, nor had the water acquired a linell of volatile alcali. When, however, this air was made to explode, the Author, on instantly applying hii nostrils to the mouth of the veílel, perceived a very evident alcaline smell: from which he infers, that the whole of the volatile al ali had not becn completely incorporated with this air ; thou o che combination was lufficiendly intiniate, to deprive the volile alcali of its property of being absorbed by water.

This curious experiment undoubiedly deserves to be repeated on a larger fcale, and the process to be carried on, till the opesator be perfectly allured that no additional explosions will prom duce any further effect on the alcaline air. The water aftere wards added so it should likewise be strictly examined. There appears here to be either an actual decomposition of the volatile aicali; or a new combination formed of it with some addicional fubliance. The queitions, accordingly, that naturally occur here are-Is its own abundant phlogiston only separated from the alcaline air, by the electric explotions, so as to constitute inflammable air; and in that cale, what becomes of its other principle or principles?-or does the electric matter conduct, from other substances, or itself furnith, more phlogiston, to the alcaline air; so as to constitute a kind of neutral compound, infoluble in water?-or lastly, is there, in this case, a disunion of principles, and an increase of dimension, effected merely by the intense heat of the electric explosions; as is hinted at pag. 385?- We ought to have premised a conjecture of the Author's

that inflammable air in general consists of phlogiston combined with some basis, which is of an alcaline nature; and that the phlogiston of this inflammable air is principally supplied by the electric matter.

The next section contains an account of some singular experimenis, chewing the remarkable volatility of that ponderous metallic iubitance, quicksilver, under certain circumstances. The evaporation of mercury in vacuo, or rather its subsequent condensation into globules, in the upper part of a barometer, had been before observed. The Author too had formerly taken notice of a black matter lining the cavity of the upper part of a glois fyphon, containing vitriolic acid air confined by mercury, when he seat clearic explotions through it: but at that time he entertaines no fufpicion that this matter came from the quicksilver; imagining that it was altogether formed from the vitriplic acid air,

Without Wi'bout mentioning his previous experiments relative to this subject, we shall only obterve, that he made the electrical explosions, in vitriolic acid air, not from the surface of the mercury itself, but between two wires, placed at the great distance 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 so near to the surface of the mercury. As this black matter on applying heat to it, was found to be mercury; it seems that the mercurial vapour must have completely and previously pervaded the whole space, filled with vie triolic acid air ; and that the electric matter found it already dila persed throughout this air, and did not produce any proper evac poration, or mechanical trusion, of the mercury, by its immediate action upon that fluid. Il even appears, from other experiments of the Author's, that mercury exists in the form of vapour, in common air : for here too the black matter is produced, though not so plentifully, and only at a finall distance above the surface of che mercury.

To these experiments succeed others-on the nitrous acid existing in metallic calces;---on the extraordinary volatility given to the nitrous acid, on its admixture with the vitriolic, from which it entirely escapes ;-and on the marine acid, depblogisia cated by means of manganese : a discovery, we believe, of Mr. Scheele's. The experiments made with the acid in this new State (in which it will, singly, dissolve gold) confirm the opinion which the Author had always entertained ; that a certain portion of phlogiston is necessary to all substances, and especially acids, assuming the form of air.' The marine acid, thus deprived of phlogiston, is actually brought into a state very nearly resembling that of the nitrous acid; being now, like it, incapable of assuming the form of a permanent air, that is, of an air that can be confined by quickliver ; which substance it immediately corrodes, forming probably with it a kind of corrosive fublimate. · Mr. Watt, in a subsequent note, properly observes that this is perhaps an easier, as it certainly is a more direct, way of making that preparation, than the common process.

In the following sections are contained--Observations on the lateral electrical explosion, formerly printed in the Philosophical

Transactions, and some miscellaneous experiments in electric city. These are succeeded by others relative to sound, 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 summary view of all the more important facts contained in this and the four preceding volumes, under distinct heads; with relerences to those parts of the work in which they are more largely treated of. This recapitulation will be found to be exceedingly useful and instructive. A sec. tion is added too, containing explanations or corrections of various passages in the four former volumes ; suggested by subsequent experiments or observations. An Appendix to this volume contains - An Extract of a Letter from Mr. Arden, defcribing a very singular appearance produced by artiņcial electricity ;-some observations on different parts of this volume, by Mr. Watt, and Mr. Bewly ;-a description, 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 spark, in a copper fark holding three pints, perfectly closed, and accurately weighed before the explosion; it was found, after the explosion, that the vesiel weighed less (generally two grains) than before.

We shall only add our wishes, that the Author, ‘now entering,' as he observes, 'on a new period of life,' (at Birmingham) may have it in his power to realise the hopes, which he expresses in his Preface, that, in his new situation, he • Thall be enabled to devote bimself, as much as in any former period of his life, to philosophical pursuits.' In there withes every friend to philosophy will, we doubt not, heartily concur with us..

Art. IV. A Régifier of the Going of Mr. Mudge's first Time-keeper,

from April 18in, 1780, to May gih, 1781: with two or her Re

gilters of the fame Time-keeper, 460. s. Cadell. 1781. TN our Review for September last, we gave a very particular

account of a watch of Mr. Arnold's making. Justice 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 expresses, three several registers of the going of the same watch, at three (somewhat distant) periods of time.

The first in point of time, though not placed so in the pamphlet, was kept by the Rev. Professor Hornsby at Oxford, from June 20th to October 31st. The year is not mentioned; but there are some reasons for fupposing 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 4:h, when it loft 2" 57, 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 1"78, and July the 31st,

when

reasons for Puppeen the rates between its tib, the true places 5, made the coup from

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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 5' 3" { in time. When it was brought up from thence, the ist of November following, it made the difference of longitude between those two places 5' ," 8 the mean of the two is 5' 2" } ; and the true longitude of Oxford, as determined by. astronomical observations, is 5' 2" W.

It was next tried at Greenwich, under the inspection of the Rev. Dr. Maskelyne, Astronomer Royal, from November the 12th 1770, to November the 30th 1777. The watch appears under rather less favourable circumstances in this trial than it did in the last; 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 leconds and a fraction, and continued to go at that rare, with most amazing regularity until the latter end of Sep!ember, when it began to accelerate again, and was gaining s" nearly when the journal is closed.

The greatest difference between its rates on any two days in these thirteen months was 72; namely, between its rates on January the ist, on which day it loft 1' 46, and November the zoth, when it gained 5" 74. ' The greatest 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 gth and its rate on January the roub. 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 discover and remove the cause of the irregularities which were observed in the watch's going;, and the success of his endea, yours will be best seen from the following account of the last of the three triais 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 person by whom this last trial was made *. It must also be acknowledged, that the comparer laboured under another disadvantage, in not being able to regulate his clock by astronomical obiervations, 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 some períons, who will not be able to object to the

: We are cold it was by Count Bruhl.

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