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We must not omit to take notice of an objection, which Dr. Priestley here anticipates and answers, that may be made to the results which he deduced from fome of his former experiments on air. From these he inferred that vegetation was one of the means employed by nature in purifying the atmosphere, by depriving it of that noxious principle with which it is charged by animal refpiration, combuftion of inflammable substances, putrefaction, &c. From the foregoing experiments a fufpicion may arife that, as his trials were made with plants growing in water, the obferved melioration of the included air might be principally effected by the emiffion of dephlogisticated air from the water in which they grew. We fhall give what he says on this subject:

It will probably be imagined that the refult of the experiments recited in this fection throws fome uncertainty on the refult of former experiments, from which I have concluded that air is meliorated by the vegetation of plants; efpecially as the water by which they were confined was expofed to the open air,. and the fun, in a garden. To this I can only fay, that I was not then aware of the effect of these circumstances, and that I have represented the naked facts, as I obferved them; and having no great attachment to any particular hypothefis, I am very willing that my reader fhould draw his own conclufions for himself.

I muft inform him, however, that my experiments at Leeds were made in a north-east window of the houfe, where the influence of the light on the water could not be very confiderable; that fome of the proceffes were completed in two days, and generally in about a week; and that the water within the jars was fo fmall, in proportion to the quantity of air, that I do not at prefent imagine that the melioration of the air at that time could have been owing to it. Besides, as I have observed, I frequently kept air in the fame expofure, with respect to water, light, and every other circumstance that occurred to me to attend to, and the fame space of time, but without any plant vegetating in it, when there was no fenfible melioration of it.'

In an Appendix to this volume are contained several papers. communicated to the Author by his Correfpondents. No and 2, contain obfervations, by Sir William Lee, on the efficacy of

in the middle of a garden. One retort, and one vial, were covered with black filk; which, at the fame time that it excluded the fun's light, communicated more beat to the water than was tranfmitted to the other retort and vial. After they had ftood a month, a large quantity of pure air, amounting to about one-ninth part of the bulk of the water in each, had been separated in the naked retort and vial whereas on taking off the filk from the other two vessels, only a bubble of air, not exceeding the fize of a small nut, was found to have been separated from the water contained in them.

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water impregnated with fixed air, in preferving meat, washed with it, from putrefaction. No 3. An account of the cure of an inflammation of the breaft, by the topical application of fixed air; by Mr. Adam Walker. No 4 and 5. Two letters from Mr. Becket of Bristol, containing accounts of fome experiments made at the Author's requeft, on the water of the hot well, and on fea water; from both which he extracted, by means of a boiling heat, air fo far dephlogisticated, as to take exactly an equal quantity of nitrous air before it increased in bulk: whereas five parts of common air required only three parts of nitrous air, to produce the fame effect; the column of air in the gage tube increafing in length, exactly in proportion to any fubfequent addition of nitrous air. No 6, contains the refults of fome experiments made by Dr. Dobfon of Liverpool, on the expulfion of air better than common air from fea water. N° 7. A letter from Mr. Magellan, on the efficacy of fixed air, experienced in a putrid cafe, in Holland. The fixed air was exhibited according to Dr. Hulme's method; and likewise in two other fuccessful cafes, afterwards related-a quartan ague, and a dropfy, under the direction of Dr. Coopmans of Franeker in Frezeland.

In N° 8, Dr. Ingenhoufz defcribes an eafy and expeditious method of procuring a fpecies of inflammable air or vapour, from vitriolic æther. A fingle drop of this liquid put into an inflammable air pistol, containing about 10 cubic inches, communicates to the common air contained in it a very strong ex- ¦ plofive force. It is very remarkable that this inflammable air or vapour exceeds the inflammable air extracted from iron, in specific gravity fo much as in the ratio of 150 to 25. It is even heavier than common air, in the proportion of 150 to 138; fo that if too great a quantity of it contained in the air pistol (and the confequent exclufion of the proper quantity of common air) prevent it from taking fire; it will fall out, on holding the pistol inverted a few feconds with its mouth open; and, in confequence of the entrance of a proper quantity of common air, in its room, the explofion will take place. We have fhewn this circumftance in the best manner, by holding the open mouth of the inverted piftol, purpofely overcharged, at a fmall diftance from the conductor of an electrical machine, while the globe was kept in motion. During fome feconds, the fparks produced no effect; but as foon as the proper quantity of inflammable vapour had fallen out, the explofion enfued.

It is, perhaps, a circumftance equally remarkable that, though æther itself is fo very volatile, and evaporates so quickly yet this elaftic vapour generated from it will remain fome hours in an open glafs, without fuch diminution from evaporation or its mixing with the atmosphere, as to deftroy its inflammable quality.

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No 9th and laft, contains fome further experiments on Pyrophori, by Mr. Bewly; who there defcribes at large the alcaline pyrophorus difcovered by him; and of which he had only spoken in general terms, in a paper printed in the Appendix to the Author's third volume of Obfervations on Air. From the prefent Article it appears that pyrophori are produced from charcoal combined either with fixed alcali, calces of iron, copper, &c. or earth of alum, nearly pure, without the prefence of the vitriolic acid in any of these compofitions; to which laft circumftance M. du Suvigny had ascribed the accenfion of all the pyrophori formed of the abovementioned fubftances combined with that acid.

The few specimens that we have given of the contents of this volume fufficiently characterife it: though we ought further to obferve that, in our review of it, we have omitted even the mention of many other important obfervations contained in it. It does not require the fpirit of divination to foretel that even fuch of the Author's experiments, as may appear the leaft fignificant, contain the germs of new difcoveries. Indeed every new fact, related by fo difcerning an obferver, is a valuable deposit thrown into the public stock; the worth of which will be best perceived by those who are beft qualified to make a proper ufe of fuch facts: not only by attending to the lights thrown by them on old or known proceffes; but by profecuting the new ideas which they fuggeft to thofe, who poffefs that spirit of combination, which is the most fruitful fource of philofophical difcoveries.

ART. II. The Canadian Freeholder: In Three Dialogues between an Englishman and a Frenchman, fettled in Canada. Shewing the Sentiments of the Bulk of the Freeholders of Canada concerning the late Quebeck-Act; with fome Remarks on the Boston Charter A&t; and an Attempt to fhew the great Expediency of immediately repealing both thofe Acts of Parliament, and of making fome other ufeful Regulations and Conceffions to his Majefty's American Subjects, as a Ground for a Reconciliation with the United Colonies in America. 8vo. Vol. II. 5 s. bound. White. 1779.

HE fubject of the Dialogue now before us, was touched upon rather than confidered in the preceding Volume *. It is an inquiry concerning the King's fole legiflative authority over countries that are conquered by the British arms, and ceded to the British Crown. In the difcuffion of this important queftion, we wholly lofe fight of The Canadian Freeholder: or at least, this character is funk in the more extenfive one of an English lawyer and hiftorian. If the gravity of the subject did not overpower any fuch irregular ideas, we fhould fuspect that Our Author had formed a plot to furprise his readers, into the

For an account of which, fee Review, vol. 57 and 58.

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perufal of a laborious legal argument, and to plunge them at once, without notice, and without preparation, into all the depths and myfteries of jurifprudence. Who would expect to find, under the title prefixed to this work, an elaborate and mafterly confutation of certain pofitions advanced by the Lord Chief Juftice of the King's Bench, in giving judgment in the cafe of Campbell and Hallt. The event of this much agitated caufe is ftill fresh in the memory of the public. Lord Mansfield did indeed decide it against the crown; but, with a dexterity peculiar to himself, he took care to obviate any inferences which might be drawn from that judgment to its difadvantage; and by eftablishing, in the broadeft terms, the following doctrine, to heal the wound which had feemingly been given by it to the prerogative-royal. His Lordship's propofition was, "That upon the conqueft of any country by the British arms, and a fubfequent ceffion of it by its former fovereign to the crown of Great Britain, the King becomes the fole legiflator of such country, and has a right to make laws for, and impose taxes on the inhabitants of it by his fingle authority, without the concurrence of the Parliament; unless the faid authority shall have been previously limited or reftrained by an act of Parliament, antecedent to such conquest and ceffion."

Though this fuppofed right should be allowed, we are not fure that the politician of the present day need be much alarmed at the confequences. Whatever terrors fuch a doctrine might have excited a century ago, we are inclined to think, that the danger to our political liberties does not grow out of this quarter. His Majefty's faithful commons were lefs complaifant, or lefs dutiful than they are in our times: and it is hardly probable, that an odious branch of the prerogative will be exerted in any inftance of fufficient magnitude to awaken the jealousy of the people, while the crown can attain all its purposes through the lefs obnoxious medium of an act of Parliament. But our Author thinks otherwife: and it must be confeffed, he maintains his opinion with much ingenuity, and ftrength of argument. As he fuppofes a cafe, which falls, perhaps, within the bounds of probability, he affails the conviction of his readers where conviction is generally moft acceffible;-by alarming their apprehenfions. He conceives, that upon the event of this question concerning the power of the crown to

+ Beiter known out of Weftminster-Hall by the name of The Granada Caufe. Lord Mansfield was of opinion, that the Crown had by the Proclamation of 23d of Oct. 1763, precluded itself from exercifing its right of impofing taxes on the inhabitants of Granada, and had transferred it to the future Governors, Councils, and Af femblies, of the said island.

levy taxes in conquered countries, the fate and political fituation of thousands, and (if we turn our eyes towards the Eaft Indies) even of millions of people may depend;' nay, he adds, that the fate of the inhabitants of Great Britain does likewife depend upon this question; for if the King should conquer and keep poffeffion of fome of the rich provinces of Indoftan, and exercife this fuppofed right of levying taxes upon them without the concurrence of his Parliament, he might foon increase his revenue to fuch a degree as to be able to pay his fleet and army, and carry on the government without the affiftance of Parliament. And in fuch an event, he might fafely Tay afide the ufe of Parliaments, as their meetings depend entirely on his pleasure, there being no law now in force, that authorises the members of either Houfe to meet at a certain time, of their own accord, without the King's fummons or appointment. And if this fhould be done, it is easy to foresee, that in a few years, the very existence of the British Parlia ment might be forgot, or become a mere historical event, known only to the fpeculative inquirers into the English history, juft as the existence of the States-General of France (who once were sharers with the Kings of that country, in the exercise of the legislative authority over it) is now known only to the lawyers and other learned men who inquire into the history of that kingdom.'

Admitting this inftance not to be ftrained, our Author has an undoubted claim to the gratitude of every friend to liberty, for combating a power fo dangerous as that which Lord Mansfield has afcribed to the Crown: but, unluckily, by starting this formidable fuppofition, which the wealth of Indoftan arms with fo many terrors, he has raised a ghoft which he finds fome difficulty in laying again. For whatever doubts may have been entertained concerning the authority of the King, to impofe new taxes on the inhabitants of conquered countries, it is generally allowed, that he may collect all the taxes legally exifting in fuch countries at the time of the conqueft, and appropriate them to whatever ufes he may think fit. The confequences of this acknowledged right are not lefs alarming than any that the ufurpation of the fuppofed right, afferted by Lord Mansfield, can be attended with. The well-imagined inftance of the rich provinces of Indoftan, is once more introduced by our Author: the wealth of this devoted country is not yet exhaufted; and he seems unwilling to leave fo dazzling a prize to the ambition of our monarchs. In pursuing this confideration, he is certainly guilty of digreffing from his fubject. We do not, in general, love digreffions; but as he ftrongly contends, that this is a matter highly proper for parliamentary investigation, we cannot, in common decency, refufe to follow fo in

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