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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 some 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 de priving it of that noxious principle with which it is charged by animal respiration, combustion of inflammable substances, putrefaction, &c. From the foregoing experiments a suspicion may arise that, as his trials were made with plants growing in water, the observed melioration of the included air might be principally effected by the emission of dephlogisticated air from the water in which they grew. We shall give what he says on this subject :
• It will probably be imagined that the result of the experi, ments recited in this section throws some uncertainty on the result of former experiments, from which I have concluded that air is meliorated by the vegetation of plants; especially as the water by which they were confined was exposed to the open air, and the sun, in a garden. To this I can only say, that I was not then aware of the effect of these circumstances, and that I have represented the naked facts, as I observed them; and have ing no great attachment to any particular hypothesis, I am very willing that my reader should draw his own conclufions for himself.
"I must inform him, however, that my experiments at Leeds were made in a north-east window of the house, where the influence of the light on the water could not be very considerable; that some of the processes were completed in two days, and generally in about a week; and that the water within the jars was so small, in proportion to the quantity of air, that I do not at present imagine that the melioration of the air at that time could have been owing to it. Besides, as I have observed, I frequentiy kept air in the same exposure, with respect to water, light, and every other circumstance that occurred to me to attend to, and the same space of time, but without any plant vegetating in it, when there was no sensible melioration of it.'
In an Appendix to this volume are contained several papers communicated to the Author by his Correspondents. No 1 and 2, contain observations, by Sir William Lee, on the efficacy of water impregnated with fixed air, in preserving meat, washed with it, from putrefaction. No 3. An account of the cure of an inflammation of the breast, 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 some experiments made at the Author's request, on the water of the hot well, and on sea water; from both which he extracted, by means of a boiling heat, air so 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 same effect; the column of air in the gage tube increasing in length, exactly in proportion to any subsequent addition of nitrous air. No 6, contains the results of some experiments made by Dr. Dobson of Liverpool, on the expulsion of air better than common air from sea water. N° 7. A letter from Mr. Magellan, on the cfficacy of fixed air, expe. rienced in a putrid case, in Holland. The fixed air was ex. hibited according to Dr. Hulme's method ; and likewise in two other successful cases, afterwards related -a quartan ague, and a droply, under the direction of Dr. Coopmans of Franeker in Frezeland.
in the middle of a garden. One retort, and are vial, were covered with black silk; which, at the same time that it excluded the sun's Gobi, communicated more beat to the water than was transmitted to the other retort and vial. After they had stood a month, a large quantity of pure air, amounting to about one-ninth part of the bulk Sf the water in each, had been separated in the naked retort and lial : whereas on taking off the folk from the other two vessels, only | babble of air, not exceeding the size of a small nut, was found to lave been separated from the water contained in them,
In N° 8, Dr. Ingenhousz describes an easy and expeditious method of procuring a species of inflammable air or vapour, from vitriolic æther. A single 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 explosive 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; so that if too great a quantity of it contained in the air pistol (and the consequent exclusion of the proper quantity of common air) prevent it from taking fire; it will fall out, on holding the pistol inverted a few seconds with its mouth open ; and, in consequence of the entrance of a proper quantity of common air, in its room, the explofion will take place. We have shewn this circumstance in the best manner, by holding the open mouth of the inverted piftol, purposely overcharged, at a small distance from the conductor of an electrical machine, while the globe was kept in motion. During some feconds, the sparks produced no effect; but as soon as the proper quantity of inflammable vapour had fallen out, the explosion ensued.
It is, perhaps, a circumstance equally remarkable that, though æther itself is so very volatile, and evaporates so quickly: yet this elaftic vapour generated from it will remain some hours in an open glass, without such diminution from evaporation or its mixing with the atmosphere, as to destroy its inflammable quality.
No gth and lait, contains some further experiments on Pyrophori, by Mr. Bewly; who there describes at large the alcaline pyrophorus discovered 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 Observations on Air. From the present Article ít 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 presence of the vitriolic acid in any of these compositions ; to which last circumstance M. du Suvigny had ascribed the accension of all the pyrophori formed of the abovementioned substances combined with that acid.
The few specimens that we have given of the contents of this volume sufficiently characterise it: though we ought further to observe that, in our review of it, we have omitted even the mention of many other important observations contained in it. It does not require the spirit of divination to foretel that even such of the Author's experiments, as may appear the least fignificant, contain the germs of new discoveries. Indeed every new fact, related by so discerning an observer, is a valuable deposit thrown into the public stock; the worth of which will be best perceived by those who are best qualified to make a proper use of such facts: not only by attending to the lights thrown by them on old or known processes; but by prosecuting the new ideas which they suggest to those, who possess that spirit of combination, which is the most fruitful source of philosophical discoveries.
Art. II. Tbe Canadian Freeholder: In Three Dialogues between an
Englishman and a Frenchman, feriled in Canada. Shewing the Sentiments of the Bulk of the Freeholders of Canada concerning the late Quebeck-Act; with some Remarks on the Boston Charter AQ; and an Attempt to sew the great Expediency of immediately repealing both those Acts of Parliament, and of making some other useful Regulations and Concessions 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. THE fubject of the Dialogue now before us, was touched
upon rather than considered in the preceding Volume *. It is an inquiry concerning the King's sole legislative authority over countries that are conquered by the British arms, and ceded to the British Crown. In the discussion of this important question, we wholly lose fight of The Canadian Freeholder: or át least, this character is funk in the more extensive one of an English lawyer and historian. If the gravity of the subject did not overpower any such irregular ideas, we should suspect that our Author had formed a plot to surprise his readers, into the
• For an account of which, see Review, vol. 57 and 58.
perusal of a laborious legal argument, and to plunge them at once, without notice, and without preparation, into all the depths and mysteries of jurisprudence. Who would expect to find, under the title prefixed to this work, an elaborate and masterly confutation of certain positions advanced by the Lord Chief Justice of the King's Bench, in giving judgment in the case of Campbell and Hallt. The event of this much agitated cause is still freth 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 disadvantage ; and by establishing, in the broadest terins, the following doctrine, to heal the wound which had seemingly been given by it to the prerogative-royal. His Lordship's proposition was, “ That upon the conquest of any country by the British arms, and a subsequent ceffion of it by its former fovereign to the crown of Great Britain, the King becomes the fole legilator of such country, and has a right to make laws for, and impose taxes on the inhabitants of it by his single authority, without the concurrence of the Parliament; unless the said authority shall have been previously limited or restrained by an act of Parliament, antecedent to such conquest and ceffion.”
Though this supposed right should be allowed, we are not fure that the politician of the present day need be much alarmed at the consequences. Whatever terrors such 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 Majesty's faithful commons were less complaisant, or less dutiful than they are in our times : and it is hardly probable, that an odious branch of the prerogative will be exerted in any instance of sufficient magnitude to awaken the jealousy of the people, while the crown can attain all its purposes through the less obnoxious medium of an act of Parliament. But our Author thinks otherwise : and it must be confessed, he maintains his opinion with much ingenuity, and strength of argument. As he supposes a case, which falls, perhaps, within the bounds of probability, he assails the conviction of his readers where conviction is generally most accessible ;-by alarming their apprehensions. He conceives, that upon the event of this question concerning the power of the crown to
+ Beiter known out of Westminster-Hall by the name of The Granada Cause. Lord Mansfield was of opinion, that the Crowo bad by the Proclamation of 23d of Oct. 1763, precluded itself from exercising its right of imposing taxes on the inhabitants of Granada, and had transferred it to the future Governors, Councils, and As, semblies, of the said illand.
levy taxes in conquered countries, the fate and political situation of thousands, and (if we turn our eyes towards the East Indies) even of millions of people may depend ;' nay, he adds, ' that the fate of the inhabitants of Great Britain does likewise depend upon this question; for if the King should conquer and keep possession of some of the rich provinces of Indostan, and exercise this supposed right of levying taxes upon them without the concurrence of his Parliament, he might foon increase bis revenue to such a degree as to be able to pay his fleet and army, and carry on the government without the affiftance of Parliament. And in such an event, he might safely Tay aside the use of Parliaments, as their meetings depend entirely on his pleasure, there being no law now in force, that authorises the members of either House to meet at a certain time, of their own accord, without the King's summons or appointment. And if this should be done, it is easy to foresee, that in a few years, the very existence of the British Parliament might be forgot, or become a mere historical event, known only to the speculative inquirers into the English history, just as the existence of the States-General of France (who once were sharets 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 instance not to be strained, our Author has an undoubted claim to the gratitude of every friend to liberty, for combating a power fo dangerous as that which Lord Mans. field has ascribed to the Crown : but, unluckily, by starting chis formidable fuppofition, which the wealth of Indoftan arms with so many terrors, he has raised a ghost which he finds some difficulty in laying again. For whatever doubts may have been entertained concerning the authority of the King, to impose new taxes on the inhabitants of conquered countries, it is generally allowed, that he may collect all the taxes legally existing in fuch countries at the time of the conquest, and appropriate them to whatever uses he may think fit. The consequences of this acknowledged right are not less alarming than any that the usurpation of the supposed right, asserted by Lord Mansa field, can be attended, with. The well-imagined instance of the rich provinces of Ihdostan, is once more introduced by our Author: the wealth of this devoted country is not yet exbausted; and he seems unwilling to leave so dazzling a prize to the ambition of our monarchs. In pursuing this consideration, he is certainly guilty of digressing from his subject. We do not, in general, love digressions; but as he strongly contends, that this is a matter highly proper for parliamentary investigation, we cannot, in common decency, refuse to follow so in