As in this fection the Author defcribes luminous fenfations, which he had excited without the affistance of light; fo in fome of the following fections he gives an account of what he calls internal founds, not excited by the vibrations of the external air, and which he had found means to produce, by preffing, dilating, or otherwise irritating the ear, at pleasure. Thefe are not to be confounded with a mere ringing, or a rumbling and confused found in the ears: for the Author has, by practice and attention, and fometimes not without pain, as in the preceding cafe, been enabled to produce a regular though not complete fcale of diftinct founds; feveral of which he can excite with certainty, whenever he pleafes. It is very fingular too, that these founds do not vary, at different times, with refpect to acuteness or gravity; as he has found, by comparing them occafionally with the notes of a fixed mufical inftrument, with which they happened to be in unifon; though he can make then louder or weaker, by increafing or diminishing the irritation.

6

For example, he fays that he could not, for a long time, excite a found in his left ear, lower than what was in unifon with the middle D of a German flute: but he has fince produced one as low as B. In his right car he can now go two whole tones lower, or down to G. In my left ear,' he adds, I can raise notes from B to about an octave above, in all the intermediate gradations, or fenfible differences; but from thence, to a great part of another octave, I cannot yet excite them, though, ftill higher, they may be raised in great plenty, but in a more confufed manner.'

Were this scale of internal founds complete, and the commodious but selfish art of playing on a man's own ears-folus cum Jolo-eafily communicable, it would be pleafant enough to behold the gefticulations of the raw proficient in this art; who could not, like the fcraper on the violin, poffibly offend any one's ears but his own. To be more ferious :-These trials of the Author give occafion to many obfervations and speculations on the organ and fenfe of hearing, that have at least novelty to recommend them to the inquifitive reader; to whofe perufal we likewife refer a fubfequent fection on the harmonical founds, or fons flutes, as the French call them; which are made on the violin, violoncello, trumpet marine, and other inftruments played on with a bow, and which are produced by means of a light preffure of the finger upon the string.

The principal part of this performance remains yet to be noticed; in which the Author propofes a new fyftem,-new at leaft at the time when this part of the work was compofed, and even when it was fent to the prefs-on the combuftion of bodies, the caufe of animal heat, and other fubjects connected with them. Under great difadvantages, and by dint of pecu

lation,

lation, without having time or opportunities either for making experiments himself, or acquiring a knowledge of many that had been made by others; the Author had formed a theory to account for thefe phenomena, which remarkably agrees with that which Mr. Crawford has lately propofed to the world; but chiefly deduced from experiments actually made by the latter. Of this laft theory, and of the experiments on which it is eftablifhed, we lately gave a particular account, in our Review for November last, page 378. Of the conformity of this last hypothesis with that of our prefent theorift the reader will judge, from the following fhort account of it; fo far as it tends to explain the theory of combuftion.

When an inflammable body, alcohol for inftance, is fuffered to flame away; nothing but phlegm, an uninflammable fubftance, can be collected from it. The alcohol therefore has been intirely decompofed; and its phlogifton, in particular, has been feparated from it. Any quantity of air too, in which this process has been carried on till the flame has gone out, is found to be faturated with this principle, which the alcohol has loft, and which conftituted it an inflammable fubftance.-Now, as the flame, fays the Author, continued only while the air was taking the phlogifton from the vapour, and went out when the air was no longer able to do this; it feems that the combustion depended intirely on fuch action of the air on the phlogiston.'

After obferving that the combination of certain fubftances with each other is attended with heat; Mr. Elliot fuppofes that the heat generated in the combuftion of bodies is occafioned by the phlogifton, contained in the inflammable body, com. bining with the air; or, to ufe his own words, that air has a greater affinity with phlogifton, than the fubftances have with which it is combined in inflammable bodies; and therefore when all circumstances properly concur, it attracts that principle from thofe bodies; that a fhining heat is generated by their combination; and that this decompofition, when once fufficiently begun in a perfectly inflammable body, together with the fhining heat which is a confequence thereof, will be continued on the principles above laid down, without any farther affiftance from extraneous heat, as long as any of the substance remains.'

Even in clofe veffels, where there is no communication with the external air, combuftion is nevertheless maintained, and that too with violence, if nitre be mixed with the combustible body: becaufe, fays the Author, it is now well known that nitre, or the nitrous acid, contains a quantity of common air, or rather indeed of air ftill more greedy of phlogifton, and therefore better adapted to promote combuftion than common air. In the process of deflagration, the phlogifton, and this

air, diflodged from their refpective bafes, fuddenly rufh into union, and produce a fhining heat.

The Author illuftrates this doctrine in various manners, and not without occafionally referring to fome known experiments, from which he deduces confequences fubverfive of the prevailing theory relative to combuftion; particularly of that part of it which fuppofes that phlogifton is combined elementary fire, let loofe, and rendered elaftic in that procefs; and that the heat and light of flame proceed from the ayolation of this difengaged principle. He acknowledges that the light proceeds from it, though the heat does not; and that the latter proceeds from difengaged fire, as chemifts indeed at prefent imagine; who are miftaken only with refpect to the origin of that fire.

Hitherto the Author's hypothefis and that of Mr. Crawford nearly correspond, though the two Writers had no communication with each other. In what follows, the prefent Author proceeds further, and varies from his brother theorift, when he inquires into the origin of the fire above mentioned. For this he accounts by an hypothes, principally founded on a variety of conjectures more or lefs probable, and inferences from a few experiments; with refpect to the attractive and repulfive powers, and other qualities, of the particles of air, fire, phlogiston, earth, and ather-not the chemical, but the hypothetical, fluid fo called.

The Author next, in a more experimental manner, confiders the phenomena of the light and colours exhibited by ignited fubftances; and then proceeds to apply fome of the preceding obfervations refpecting combuftion, to refpiration and animal heat (proceffes that bear a ftrong analogy to it), as well as to mufcular motion. But here we must refer the Reader, who has a tafte for fpeculations of this kind, to the work itfelf for information. The Author has given a favourable fpecimen of his ingenuity, at least, in fabricating a fyftem principally founded on fpeculation, that carries any face of confiftency in it, with fuch delicate and difficult materials to work upon as thofe above -recited; the properties of fome of which are not well afcertained, and the very exiftence of one of them at least, is very problematical. Indeed it appears that the Author's fituation and circumstances have not furnished him with opportunities of following the more fafe and fober mode of ftrict experimental investigation. It would be unfair, therefore, and invidious in us, to mark any defects that we may have obferved in an attempt of this kind, made by a perfon thus circumftanced. For the fake, however, of the Author, as well as of thofe who perufe his performance, we take a pleafure in complying with a request, which he has tranfmitted to us by letter, to convey to

the

the public the following additional obfervations, where he rectifies his own errors, and this we fhall do in his own words.

• Since the book was published,' fays Mr. Elliot, in his letter to us, I have, by a more attentive comparison of it with Mr. Crawford's admirable difcoveries, convinced myself that I had erred in my idea of the manner in which fire exifts in bodies; though a prepoffeffion in favour of my own theory hindered me from perceiving it before.-I had imagined that it exifted in bodies only in its elaftic ftate, as defcribed in the first five cafes of the feventh fection. When air is heated and cooled, the phanomena seem to answer to that theory; and do not the expanfion of bodies, and the feparation of their particles by heat, depend on the fame principle? Fixable air, however, is not much lefs elaftic than common or dephlogisticated air; though the former, by Mr. Crawford's experiments, contains 67, and the latter near 300 times more fire. Their fpecific gravities are to one another only as the numbers 281, 187, 185, or thereabout; and, confequently, the fire which is extricated by phlogiston was in a fixed or combined ftate. And, with regard to their elafticities, I have this to obferve; that, as bodies which contain moft phlogiston refract light moft ftrongly; fo bodies which contain the greatest quantity of fire in a fixed state attract elastic fire most powerfully in the manner defcribed in the cases above alluded to. But, as happens with the refraction of light, this difference will be but fmall, though the different proportions of fire in the bodies be very great, and only perhaps fuch as to anfwer to the numbers given above. The elafticity of air, the expanfion of bodies by heat, and the feparation of their particles, depend therefore on thefe principles;-the fenfible heat, on the attraction of bodies for fire, or abfolute heat, according to the law in Cafe 11th, &c. and their abfolute quantities of fire, on the quantity of phlogifton, and the force of its combination; or, in other words, on the attraction of those bodies for fire. It appears, therefore, that I was right enough in my facts in these cales; but, through not diftinguifhing the two kinds of attraction, wrong in my manner of explaining them."'

On the whole, we cannot help being greatly prejudiced in favour of our prefent theorift; on account of the many marks of real ingenuity exhibited in this performance; particularly in the theory relating to combuftion and refpiration. His merit in this refpect is the greater, as it evidently appears, from various paffages that occur in this work, that his neceffary avocations, and other circumftances, had not enabled him to know what had been done by others, or to make the neceffary experiments himfelf. He is entitled to equal praife on account of his unaffuming manner, and the great candour, and even warmth, with

which

which (in an Appendix written after his having feen Mr. Crawford's publication, while his own performance was at the prefs), he praises the work of a man, who, in point of time, had anticipated him in the publication of a capital difcovery; and had thereby robbed him of a part, at leaft, of the glory which he expected to derive from it.

Such inftances are rare among philofophers; and, in the prefent cafe, are fufficient to cover a greater multitude of fins (against philofophy) than are to be met with in this perform

ance.

ART. VIII The Evidence of Reason in Proof of the Immortality of the Soul, independent on the more abftrufe Inquiry into the Nature of Matter and Spirit. Collected from the Manulcripts of Mr. Baxter, Author of the Inquiry into the Nature of the human Soul, and of Matho, To which is prefixed, a Letter from the Editor to the Rev. Dr. Priefley. Svo. 7 s. bound. Cadell. 1779.

T Phy

HOSE who are acquainted with, and admire, the metaphyfical writings of the late Mr. Baxter, will think the world much obliged to Dr. Duncan for the prefent publication; and for refcuing from oblivion the papers which he left behind him in which he had collected together fuch proofs of the immortality of the human foul, as were independent on the metaphyfical fubtleties concerning its effence, its materiality or immateriality. In a prefatory letter, addreffed to Dr. Priestley by the editor, the latter gives an account of the circumftances by which he was enabled, and induced, to preferve these remains of a refpectable writer, and to methodife and arrange them in fuch a manner as to render them fit for the infpection of the public.

Upon the rife of the late controverfy concerning the materi ality of the foul, Dr. Duncan conceived a defire of offering his fentiments on the fubject. He wished, however, to fee the public attention diverted from a metaphyfical difpute, which, in the opinion of fome, threatened great mifchief to the moral world; though, in the judgment of others equally well in tentioned, no prejudice was likely to enfue, either to religion or morals, from fuch a controverfy; of which scarce one in twenty of thofe, who, at this day, pafs for learned men, have ever properly confidered the first principles.'-In short, he ftudied to place in a clear and ftriking light, the arguments which natural reason fuggests in proof of a life to come, from the faculties of the human mind; from the moral law, written by the finger of God in the heart of man, and the voice of conscience, enforcing our obfervance of it; from the relation in which we ftand to the Creator and Supreme Ruler of the univerfe; from his known perfections, in fhort; confidered refpectively to the present ftate of his intelligent fubjects upon earth."