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 expreffes that monotone, or fameness of voice, which, he fays, 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 expreffive of awe, amazement, and admiration, is exceedingly fuitable to folemn, grand, and magnificent fubjects.' If dying excellence deferves a tear, If fond remembrance' ftill is cherished here', His fame requires we act a tenderer part:' From fōnd fidelity's domeftic' woe, So much are Garrick's' praise-so much' his due'— It is impoffible, as our author obferves, to convey that juftnefs of pause, that melody of voice, and that dignity of manner, which diftinguish a good speaker. Thefe are among the perishable beauties defcribed in the Monody. But there are beauties of an inferior kind, which are not fo incommunicable; and they, who attentively perufe what is faid on the fubject in this work, will not think that notation, which conveys to us a variety of juft and pleafing inflexions, though unaccompanied with every other excellence, either an incurious or a useless discovery. Experiments and Obfervations relating to the various Branches of Natural Philofophy; with a Continuation of the Obfervations on Air. The Second Volume. By Jofeph Priestley, LL. D. F. R. S. c. 8vo. 6s. Johnson. WE E inform the public, with great pleasure, that this, though the fifth, is not likely to be the laft volume, of Dr. Priestley's philofophical productions. In his preface he feeds feeds our expectation with the moft flattering promifes-He tells us, that in confequence of fome happy revolution in his circumftances, he may be confidered as entering upon a new period of life; and that the volume before us is the refult of an inclination to clofe his philofophical accounts, as they stand at prefent, and to open a new one. We feel warm in the hope that the fuccefs of his fingular toil and ingenuity may be in proportion to the advantageous change by which they are favoured. We fhall, however, be amply fatisfied if he proceeds with the rapidity and fplendour which have hitherto crowned his exertions. In the numerous catalogue of Dr. Priestley's difcoveries there is not one more curious, or better fupported 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 refpiration of animals, and other circumftances which render it noxious. The first fection of this volume confirms what he has before faid on this fubject: his preceding volume informed the public of a fingular property, by which the willow plant abforbed air of different kinds, but inflammable air in the greatest abundance: he has fince made a variety of experiments, from which we learn the following particulars. 1. Inflammable air, after the abforption of the willow plant, is difcharged purified from its phlogiston by the plant, which had retained this noxious principle for its own nourishment. 2. He confirms an hypothefis which he had formerly supported, viz. that nitrous air is noxious as well to vegetable as to animal life. 3. It appears from this fection that in fome inftances the willow plant may really abforb a greater quantity of inflammable air than it can digeft. In this cafe, the air, which it difcharges after abforption, 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 wifdom of nature, as it is evident from the growth of this willow plant in marfhy places, where a great quantity of inflammable air is continually difcharged. Sect, II. may, we think, be confidered as the moft curious and entertaining part of this work. In an appendix to his laft volume, Dr. Priestley announced his difcovery of that great influence which light has upon water, or upon the air, which, in confequence of being expofed to the fun, is produced from that wa ter. Dr. Ingenhoufz purfued the enquiries which this difcovery fuggefted, and wrote a whole volume, in which we are by no means convinced of his making proper acknowledgements to the fource whence he derived his materials. Our readers may remember, that Dr. Priestley filled two jars with pump pump water, one of which was placed in the dark and the other exposed to the fun. In the former, after continuing for Some time in the fame circumftances, no air was produced. But in the latter, after ftanding a few days, a green matter was depofited, 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 difcovered to be a vegetable, whofe form and other peculiarities were most clearly feen through a microfcope, by his friend Mr. Bewley. A An acquaintance with the nature of this green matter has led the Doctor to prove moft clearly, that its operations refemble thofe 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 hypothefis are, in our opinion, decifive. By expofing water which contained no air to the light in a jar inverted in mercury, no effects were produced. By 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 copioufly 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 fun, to produce effects fimilar to thofe already enumerated: a handful of thefe water-plants were put into a receiver containing eighty ounce measures of water, inverted in a bason of the fame; after standing three days, they had emitted eight ounce measures of air, which was found to be much purer than common air; from which, as well as from other experiments, the Doctor infers, that in thefe experiments the air is generally in proportion to the capacity of the veffel; and that during the whole process it feldom exceeds one-eighth of the quantity of water. The Doctor concludes this fection with obferving, that the experiments recited in it may help us to explain, why water, after iffuing from the earth and employed in floating meadow land, becomes in time exhaufted of its power of fertilizing it. When it iffues from the earth, it contains air of an impure kind; that is, air loaded with phlogifton. This principle, the roots of the grafs extract from it, fo that it is then replete with dephlogisticated air, and confefequently the plants it afterwards comes into contact with find nothing in it to feed upon.-I believe it is commonly imagined that the water depofits fomething in its courfe upon the earth of its bed, and by that means becomes effete and incapable of nourishing plants.' Dr. Priestley, in his third fection, gives the diftinguishing properties of the plant which forms the green matter; its length proves it not to be the conferva fontinalis; its feeds float invifibly in the air, and will penetrate into water through the fmallest apertures in the glafs. 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 fo 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. Priestley concludes this fection with an experiment defigned to prove in what part of the veffel the feeds of this plant would first fall, and we are aftenifhed he fhould not repeat the experiment, but leave a decifion to conjecture, which might have been made with fuch little trouble. We cannot give a better general view of the contents of the fourth fection than that which the Doctor himself has given. Having very foon obferved that this green vegetable matter, or water mofs, was planted and propagated with more ease, and produced air more copioufly, in fome circumstances than in others, and that various fubftances, animal or vegetable, were favourable to it, and others of both kinds unfavourable; I tried a great variety of them, and fhall recite fuch of the particulars as appear in any measure remarkable, and fuch as may furnish hints for the farther investigation of what relates to this fubject. The most remarkable circumstance attending thefe experiments was, that fome fubftances, concerning which I could have had no fuch expectation a priori, instead of admitting the growth of this plant, when they began to putrify and diffolve, which was the cafe with moft 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 fhade. Whereas other fubftances, which, if they had been confined by quickfilver, would have yielded, by putre faction, inflammable air alfo, together with a portion of fixed air, only fupplied the proper pabulum for this green matter, and the whole produce was pure dephlogisticated air; the phlogiston, which in other circumftances would have been converted into inflammable air, now going to the nourishment of this plant, which, by the influence of light, yields fuch pure air.' It should be attended to, that, in the numerous experiments following thefe obfervations, of all the materials employed onions onions were those which admitted of the green matter with the greatest difficulty. In one part of this fection Dr. Prieftley informs us, that he found a piece of cabbage, which he had exposed in his jar for fome time, very soft but not at all offenfive. He fupposes that the green matter had absorbed all the phlogifton of this fubftance, to which alone he afcribes the of fenfiveness of smells.—What reason is there for acceding to this theory? In that general decompofition which takes place, when a body begins to part with its phlogiston, many other component parts of the body fly off. And why fhould we afcribe to the phlogifton what may (as far as we know) with equal propriety be ascribed to any of the other ingredients which are let loose at the fame time? We know of no experiment which gives a decifion in this cafe, but should rather wave acceding to the Doctor's hypothefis, till by the fame hypothefis he can account for the different fmells which proceed from different bodies in putrefaction. Ought not the putrid fmell of fish to be the fame with the putrid fmell of flesh, if they depended on the operations of the fame fimple agent? It may be faid, that in these different cafes, the phlogifton is differently modified. We think this language, which has of late been too commonly ufed, 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 trifling as to the conviction or fatisfaction which it gives an inquifitive mind. But, perhaps, the Doctor may have reafons for adopting this theory, to which we may be utter ftrangers; 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 fingular degree, of affording a nidus to the feeds of the green matter. It is the animal fubftance which of all others is most likely to putrify in water, and probably it may derive its power of producing the green matter from a wife appointment of the Creator. Dr. Priestley obferves, that the ef fect of light upon bodies putrefying in water may have a very falutary tendency in hot countries.-Undoubtedly, if the doctor could prove that in hot countries the fmalleft part of the putrified bodies were immerfed in water; and again, immerfed in fuch a manner (which is by no means probable) that the furfaces of these bodies were never expofed to the air; for in fuch circumstances it is well known, from an experiment recited in |