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tempted to mark them, as they occurred in Mrs. Yates's pronunciation of Mr. Sheridan's Monody in Memory of Mr. Garrick. The horizontal line expresses that monotone, or sameness of voice, which, he says, good pronouncers of verse often introduce to the greatest advantage.
This monotone, he adds, generally falls into a lower key, and, as it is naturally expressive of awe, amazement, and admiration, is exceedingly suitable to solemn, grand, and magnificent subjects.'
• If dying excellence' deserves a tear",
His fame' requires we act a tenderer' part;'
Thē gēneral voice, the need of mournful verse',
As on this spot'-one tear' beftow'd by you." It is impossible, as our author observes, to convey that juftness of pause, that melody of voice, and that dignity of manner, which diftinguish a good speaker. These are among the perishable beauties described in the Monody. But there are beauties of an inferior kind, which are not so incommunicable; and they, who attentively peruse what is said on the subject in this work, will not think that notation, which conveys to us a variety of just and pleasing inflexions, though unaccompanied with every other excellence, either an incurious or a useless discovery.
Experiments and Observations relating to be various Branches of
Natural Philofophy; with a Continuation of the Observations on Air. The Second Volume. By Joseph Priestley, LL. D.
F. R. S. &c. 8vo. 6s. Johnson. WE inform the public, with great pleasure, that this,
though the fifth, is not likely to be the last volume, of Dr. Priestley's philofophical productions. In his preface he K3
feeds our expe&tation with the most flattering promises-He teils us, that in consequence of some happy revolution in his circumstances, he may be considered as entering upon a new period of life ; and that the volume before us is the result of an inclination to close his philosophical accounts, as they stand at present, and to open a nezu one. We feel warm in the hope that the success of his fingular toil and ingenuity may be in proportion to the advantageous change by which they are favoured. We shall, however, be amply satisfied if he proceeds with the rapidity and splendour which have hitherto crowned his exertions.
In the numerous catalogue of Dr. Priestley's discoveries there is not one more curious, or better supported by the evidence of experiments, than that which evinces the great use of vegetables, in purifying the atmosphere after it has been corrupted by the respiration of animals, and other circumstances which render it noxious.' The firit section of this vclume confirms what he has before said on this subject: his preceding volume informed the public of a singular property, by which the willow plant abforbed air of different kinds, but inflammable air in the greatest abundance: he has since made a variety of experiments, from which we learn the following particulars, 1. Inflammable air, after the absorption of the willow plant, is discharged purified from its phlogiston by the plant, which had retained this noxious principle for its own nourishment. He confirms an hypothesis which he had formerly supported, viz. that nitrous air is noxious as well to vegetable as to animal life.
from this section that in fome instances 'the willow plant may really absorb a greater quantity of inflammable air than it can digeft. In this case, the air, which it discharges after absorption, is a mixture of pure and inflammable air; for, by applying a candle to this mixture, it goes off with a loud explosion. 4. The Doctor very pertinently points out the wisdom of nature, as it is evident from the growth of this willow plant in marshy places, where a great quantity of inflammable air is continually discharged. Sect, II. may, we think, be considered as the most curious and entertaining part of this work. In an appendix to his last volume, Dr. Prieltlcy announced his discovery of that great influence which light has upon water, or upon the air, which, in consequence of being exposed to the sun, is produced from that water. Dr. Ingenhousz pursued the enquiries which this discovery suggested, and wrote a whole volume, in which we are by no means convinced of his making proper acknowledgements to the source whence he derived his materials. Our readers may remember, that Dr. Priestley filled two jars with
pump water, one of which was placed in the dark and the other exposed to the sun. In the former, after continuing for some time in the same circumstances, no air was produced. But in the latter, after standing a few days, a green matter was deposited, whence a quantity of air was emitted, which upon examination was found to be much purer than common air. The Doctor informs us, in this volume, that the green matter which appeared in this experiment, is discovered to be a vegetable, whose form and other peculiarities were most clearly seen through a microscope, by his friend Mr. Bewley.
An acquaintance with the nature of this green matter has led the Doctor to prove moft clearly, that its operations resemble those of other vegetables in open air : that, by feeding on the noxious principle contained in the air, with which the water is impregnated, it purifies that air. His experiments produced in defence of this hypothesis are, in our opinion, decisive. By exposing water which contained no air to the light in a jar inverted in mercury, no effets were produced. putting a quantity of the green matter, taken from water which had discharged all its air, into a jar of fresh water, pure air was produced as copiously as before. And, farther, by examining the air in any particular water, before and after the green matter was depofited from, or placed in it, he found that the green matter had always purified that air. Aquatics of different kinds were found, on being introduced into a jar of water and exposed to the sun, to produce effects similar to those already enumerated : a handful of these water-plants were put into a receiver containing eighty ounce measures of water, inverted in a bason of the same; after standing three days, they had emitted eight ounce measures of air, which was found to be much
than common air; from which, as well as from other experiments, the Doctor infers, that in these experiments the air is generally in proportion to the capacity of the vessel ; and that during the whole process it feldoin exceeds one-eighth of the quantity of water. The Doctor concludes this section with observing, that the experiments recited in it may help us to explain, why water, after ifluing from the earth and employed in floating meadow land, becomes in time exhauited of its power of fertilizing 'it. When ir issues from the earth, it contains air of an impure kind ; that is, air loaded with phlogiston. This principle, the roots of the grafs extract from it, so that it is then replete with dephlogisticated air, and contesequently the plants it afterwards comes into contact with find nothing in it to feed upon. I believe it is commonly imagined that the water deposits something in its courle upon the earth
of its bed, and by that means becomes effete and incapable of pourishing plants.'
Dr. Priestley, in his third section, gives the diftinguishing properties of the plant which forms the green matter ; its length proves it not to be the conserva fontinalis ; its feeds float invisibly in the air, and will penetrate into water through the smallest apertures in the glass. It feeds upon phlogiston, and grows in great abundance when putrid flesh is put into a jar of water. But the air in the water may be so much loaded with the noxious principle as to prevent the air oozing out of the plant from being pure. The green matter will, moreover, appear in water impregnated with falt, or nitre ; but it seems probable that water impregnated with fixed air, will not admit of its growth, till the fixed air has escaped. Dr. Prieftley concludes this fection with an experiment designed to prove in what part
of the vessel the seeds of this plant would first fall, and we are astonished he should not repeat the experiment, but leave a decision to conjecture, which might have been made with such little trouble,
We cannot give a better general view of the contents of the fourth section than that which the Doctor himself has given.
• Having very foon observed that this green vegetable matter, or water moss, was planted and propagated with more ease, and produced air more copiously, in fome circumstances than in others, and that various substances, animal or vegetable, were favourable to it, and others of both kinds unfavourable; I tried a great va• riety of them, and shall recite such of the particulars as appear in any measure remarkable, and such as may furnish hints for the farther investigation of what relates to this subject.
• The most remarkable circumstance attending these experiments was, that some substances, concerning which I could have had no such expectation a priori, instead of admitting the growth of this plant, when they began to putrify and diffolve, which was the case with most vegetable and animal substances, yielded from themselves a very great quantity of inflammable air; and it made no difference whether they were placed in the fun or in the shade. Whereas other substances, which, if they had been confined by quicksilver, would have yielded, by putre faction, inflammable air also, together with a portion of fixed air, only supplied the proper pabulum for this green matter, and the whole produce was pure dephlogisticated air ; the phlogiston, which in other circumstances would have been converted into inHammable air, now going to the nourishment of this plant, which, by the influence of light, yields such pure air.'
It should be attended to, that, in the numerous experiments following these obseryations, of all the materials employed, onions were those which admitted of the green matter with the greatest difficulty. In one part of this section Dr. Prieftdey informs us, that he found a piece of cabbage, which he had exposed in his jar for some time, very soft but not at all offenfive. He supposes that the green matter had absorbed all the phlogiston of this substance, to which alone he ascribes the offensiveness of smells. - What reason is there for acceding to this theory? In that general decomposition which takes place, when a body begins to part with its phlogiston, many other component parts of the body fly off. And why should we ascribe to the phlogiston what may (as far as we know) with equal propriety be ascribed to any of the other ingredients which are let loose at the same time? We know of no experiment which gives a decifion in this case, but should rather wave acceding to the Doctor's hypothesis, till by the fame hypothesis he can account for the different smells which proceed from different bodies in putrefaction. Ought not the putrid smell of fish to be the same with the putrid smell of flesh, if they depended on the operations of the fame simple agent? It may be said, that in these different cases, the phlogiston is differently modified. We think this language, which has of late been too commonly used, is nothing more than a specious mode of concealing, under a mere name, the ignorance we cannot remove: it is, in other words, employing the occult quality of the ancients, and is equally trilling as to the conviction or satisfaction which it gives an inquisitive mind. But, perhaps, the Doctor may have reasons for adopting this theory, to which we may ter strangers; we have, therefore, only to wish that he had referred us to them, or laid them before the public.
The next section is nearly connected with those sections we have already reviewed ; it contains a number of experiments relating to the effect of expofing animal substances in water to the light and in the dark. It appears that fish have the property, in a singular degree, of affording a nidus to the feeds of the green matter. It is the animal substance which of all others is most likely to putrify in water, and probably it inay derive its power of producing the green matter from a wise appointment of the Creator. Dr. Priestley observes, that the effect of light upon bodies putrefying in water may have a very salutary tendency in hot countries. --Undoubtedly, if the doctor could prove that in hot countries the smallest part of the putrified bodies were immersed in water; and again, immersed in such a manner (which is by no means probable) that the surfaces of these bodies were never exposed to the air ; for in such circumstances it is well known, from an experiment recited in