dephlogisticated air as would fill a cylindrical jar four inches and an half long, and one inch and three quarters diameter.

The air being taken away, an equal quantity of dephlogifticated air, of equal or ftill greater purity, was collected from the fame leaves during the remainder of the evening, and the next forenoon, without taking them out of the water. This quantity of air greatly furpafles the bulk of the leaves themfelves; and fhews, fays the Author, to how amazing a quantity the air may amount, that is yielded in a fair day by a lofty tree.'

Twenty-feven fingle leaves of a walnut tree were expofed in the fame manner to the fun-fhine, in a fair warm day, from eleven till five o'clock; where they had yielded about one ounce measure of good dephlogifticated air.'

The Reader will likewife naturally wish to know the quality, or the degree of purity, of the dephlogisticated air which the Author obtained in this manner, from the leaves of vegetables. To enable him to form fome estimate on this head, we fhall firft obferve, that in this air the flame of a wax taper not only burned with fuch a degree of brightness that it dazzled the Author's eyes; but it excited a crackling hiffing which accompanies the flame when plunged in pure dephlogisticated air.' In fome cafes, fix measures of nitrous air were required, before the faturation of two measures of this air from vegetables could be obtained; and above five-eighths of the bulk of the two airs were destroyed. He had not yet however been fo fortunate as to procure from the leaves of vegetables any air fo pure as that which he obtained from the green matter mentioned in the beginning of this article, as difcovered by Dr. Prieftley; two measures of which, according to the prefent Author, required eight measures of nitrous air to faturate it; andths of the bulk of the two airs were deftroyed. The pureft dephlogifticated air expelled by fire from red precipitate, being treated in the fame manner, the Author found that ths of both airs had been deftroyed when the faturation was completed.

It is true that to every one of the experiments here defcribed, there is annexed a number, fill more accurately denoting the respective degrees of purity of the different airs obtained in each trial. But this manner of afcertaining the quality of the air depends on a peculiar mode of examination invented by the Abbé Fontana; for which we must neceffarily refer our readers to the work itself, where it is particularly defcribed; and the defcription is accompanied with a plate reprefenting all the inftruments employed in this examination. This method is faid to be fo very accurate, that, in ten fucceffive trials, in which three meafures of nitrous air are fucceffively added to two measures of common air, there was feldom a difference of more than a 500th

part

part in the refult, or in the bulk of the air remaining in the tube. The utility of this method will appear the more confpicuous, if it be true, as the Author alleges, that the refults of the trials will not be in the leaft degree disturbed or affected by any difference in the strength or quality of the nitrous air employed.

The preceding experiments ftrongly confirm the idea, that the action of vegetables upon air, at leaft in the day, is directly oppofite to that of animals. The latter infpire the common atmofpherical air into their lungs, and then emit it from thence, loaded with a foreign, phlogistic, and noxious principle: whereas vegetables, abforbing common air, retain, by fome peculiar œconomy, the phlogiftic matter it naturally contains, for their nourishment or other purposes; and then emit the air, thus rendered pure or dephlogifticated, as being, to them, noxious, or excrementitious. Dr. Priestley's early experiments have shewn that plants thrive in phlogisticated air; and his later trials, as far as he has carried them, feem to prove, on the contrary, that dephlogisticated air is injurious to them.

We have already obferved, that all plants emit a noxious air at night, or in the dark; but its quantity, fays the Author, is fo inconfiderable, in comparison of that of the dephlogisticated air which they yield in the day, that it amounts to very little. On a rough calculation, he estimates that the poisonous air, yielded during a whole night, does not amount to an hundredth part of the dephlogisticated air which the fame plant would emit during the space of two hours, in a fair day.

The roots, and flowers of plants, however, at least all of the latter kind which the Author could find in his neighbourhood, emit a poisonous air, both by day and by night, though generally in a small quantity. A few flowers of the honeyfuckle (caprifolium) exposed even to the fun's light in the middle of the day, rendered a body of air equal to two pints highly noxious, in three hours. Thefe flowers, fays the Author, like all others, after having thus rendered truly fatal a body of air equal to two pints, have loft nothing of their flavour [fragrance]. The air itself, which they have poifoned, is impregnated with the fame fragrant smell as the flowers themselves :'-fo that a perfon fhut up in a small and close room, containing a large quantity of the most fragrant flowers, might lofe his life by this moft treacherous of all poifons. The Author has heard of more than one inftance of sudden deaths, which were too probably occafioned by this hitherto unfufpected cause.

Two dozen of young and fmall French beans inclofed, during one night, in an inverted quart jar, containing only common air, rendered it fo poisonous, that a young and lively chicken put into it inftantly fell down motionlefs; and though taken out in lefs than 20 feconds, and immediately put into a

jar

jar full of dephlogisticated air, it was not restored to life, even by this powerful antidote.

After this work had been nearly printed off, the Abbé Fontana communicated to the Author a method, which he had difcovered only a few days before, of procuring to a fick perfon the benefit of breathing any quantity of dephlogisticated air, at a very cheap rate. Though we are not fo fanguine as the Author in his expectations that this important defideratum in medicine has been accomplished, by the discovery of this method; we fhall lay the principles on which it is founded before the Reader, together with the Author's conclufions from them.

The Abbé fills a large glass receiver half full of dephlogisticated air extracted from nitre (by means of heat), fo that it may contain about 500 cubic inches of this air; or a quantity fufficient to serve a perfon for breathing during half an hour. The perfon inspires this air through a bent tube introduced into it, through fome lime-water in which the receiver floats, and then expires it back again. This air returning from the lungs, fays the Author, is infected by fixed air, which being immediately abforbed by the contact with lime water, the dephlogifticated air is reftored very near to its former purity.' He then proceeds to estimate the quantity of air rendered noxious by refpiration, in a given time.

We confume, by each infpiration, about 30 cubic inches of air; and thus, allowing 15 infpirations for a minute, we confume each minute 450 cubic inches of air. The Abbé Fontana found that the dephlogifticated air being, after each refpiration, purified again by the lime-water, will remain good about thirty times as long as it would when breathed in the ordinary way; and that thus the quantity of dephlogifticated air neceffary for one minute will now ferve for breathing during half an hour; and thus the expences will be thirty times lefs.'

The Author proceeds to obferve that we confume, in the fpace of twenty-four hours, about 21,600 cubic inches of air. One pound of nitre yields by heat about 12,000 cubic inches of dephlogisticated air; and thus it yields more air than any patient could confume by breathing this beneficial air the whole day (for we must allow at least twelve hours in the twenty-four for fleeping and neceffary occupations), because this quantity will ferve thirty times longer by the method explained, than in the ordinary way. It follows by this, that the expences required for breathing a whole day dephlogisticated air cannot amount to one filling.

I have only just time enough, adds the Author, to announce this happy discovery to the Public; whofe great utility will, I truft, foon be found in the curing of inflammatory and

I

putrid

putrid diseases, &c. in which too great a quantity of inflamma→ ble principle is let loofe in our blood.'

We certainly fhould not take upon us to question the truth of any matter of fact alleged by authorities fo refpectable as thofe of the Abbé Fontana and the Author. But as no actual trial is faid to have been made of this method, we may be allowed to exprefs our doubts with respect to a mere fpeculation, founded too, as we apprehend, on an erroneous principle; or on the fuppofition, avowed by the Author, that air is rendered noxious in refpiration, because the lungs communicate to it a confiderable portion of fixed air, which is generated in our body, and thrown out from the lungs as excrementitious.'-It is true, that the pureft air which we infpire returns from the lungs in a ftate which indicates the prefence of a portion of fixed air in it and were this the only taint that it received from that organ, lime-water might reftore this air to its former purity: but it is, we believe, certain that the principal poifon infufed into it, during its ftay in the lungs, is phlogifton; to which limewater is not, or at leaft is not known to be, a proper antidote, or even a corrective.

The air contaminated by the burning of a candle in it, or by various other phlogistic proceffes, exhibits fimilar marks of the prefence of fixed air in it, if it is expofed to lime-water: but we have never heard that it has been very fenfibly mended by that circumftance. A fmall portion of fixed air may indeed be separated from it; but it continues, we apprehend, as much phlogifticated as before.

The obfervations related in this work are fo remarkable, and deserve fo highly the confideration of philofophers, that we cannot take our leave of the performance without recommending the perufal of it to our philofophical readers; as likewise the repetition, and authentication, as well as the further profecution, of the Author's experiments, during the approaching feafon of fun-fhine; and when the whole vegetable creation shall have put forth their leaves, to perform, in the midst of innumerable other good offices, the falutary office here afcribed to them.

ART. IV. The Valetudinarian's Path Guide; or, the Means of obtaining long Life and Health. Dedicated to the Earl of Shelburne. By Philip Thickneffe. 8vo. 3s. 6 d. Dodfley. 1780.

A

VAILING ourfelves of a hint furnished us by the Author,

we need no otherwife characterife this performance, than by obferving that, after the most diligent perufal of it, with our beft fpectacles mounted, we cannot find a better reason for his turning medical writer and advifer, than his being turned of forty.' We should not however, without the Author's fub

fequent

fequent information, have gueffed that he had acquired the accumulated medical wisdom of a man turned of fixty.' We congratulate him on his avowed corporeal vigour; though we muft confefs that the cause to which he seems to afcribe it, is a very fingular one-nothing lefs than the frequently partaking of the breath of young virgins*. But let us hear the Author himself:

I am myself, fays he, turned of fixty, and in general, though I have lived in various climates, and suffered severely both in body and mind; yet having always partaken of the breath of young women, whenever they lay in my way, I feel none of these infirmities which fo often ftrike my eyes and ears in this great city [Bath] of fickness, by men many years younger."

Among all the cafes of air rendered noxious by the breath, we do not recollect that Dr. Prieftley has been fagacious or gallant enough to make any exception in favour of that of young women. In the heyday of our blood, indeed, we remember we were wont to find it very balmy and delectable: but, as our pulfes beat at prefent, we own we should now dread the partaking of it; efpecially in the Author's manner,- from young women lying in our way'-as much as that of roses and honeyfuckles; which, as Dr. Ingenhoufz has lately told us t, with all their fragrance, are very treacherous and dangerous companions to those who snuff their breath too largely.

Nevertheless, a man may attain a great age, our Medical Adviser obferves, if he can hit upon the right method.' And, that the breath of youthful women may be one means of obtaining this end, is by no means improbable.'-He acknowledges, however, that Attila, King of the Huns, lived to an hundred and twenty-four, and then died of excefs, the first night of his fecond nuptials, with a beautiful Princess.'-Stifled with roses, we suppose.

The Author nevertheless perfifts in his opinion; and afterwards obferves, that the brifk and lively motion in the blood of young people is the cause of their health, vigour, and growth;' and he can fee no reafon to doubt but that the re-refpiring their breath may rouze the fluggish circulation of men advanced

• This pleafing prefcription' which, the Author tells us, can no where befo easily made up, or be fo repeatedly had,' as at Bath; or fo conveniently conveyed by the most lovely of the fex,' is to be found, it seems, in an ancient infcription, given in Reinefius's Supplement to Gruter's works. It records the death of L. CLAUDIUS HERMIPPUS [now, perhaps, Redivivus, in the perfon of the Author] who lived 115 years and five days, by partaking of the breath of young virgins'-" PUELLARUM ANHELITU."

+ See the foregoing Article. REV. May 1780.