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As in this fe&tion the Author describes buminous fenfations, which he had excited without the assistance of light; lo in some of the following sections 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 pressing, dilating, or otherwise irritating the ear, at pleasure. These 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 sometimes not without pain, as in the preceding case, been enabled to produce a regular though not complete scale of distinct sounds; several of which he can excite with certainty, whenever he pleases. It is very singular too, that these sounds do not vary, at different times, with respect to acuteness or gravity; as he has found, by comparing them occasionally with the notes of a fixed musical instrument, with which they happened to be in unison; though he can make thein lauder or weaker, by increasing or diminishing the irritation.
For example, he says 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 since 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 sensible differences; but from thence, to a great part of another octave, I cannot yet excite them, though, still higher, they may be raised in great plenty, but in a more confused manner."
Were this scale of internal founds complete, and the commodious but selfish art of playing on a man's own ears-falus cum Jolo-easily communicable, it would be pleasant enough to behold the gesticulations of the raw proficient in this art; who could not, like the scraper on the violin, pollibly offend any one's ears but his own. To be more serious :--These trials of the Author give occasion to many observations and speculations on the organ and sense of hearing, that have at least novelty to recommend them to the inquisitive reader ; to whose perufal we likewise refer a fubfequent section on the barmonical founds, or fons flutés, as the French call them; which are made on the violin, violoncello, trumpet marine, and other instruments played on with a bow, and which are produced by means of a Dight pressure of the finger upon the ftring.
The principal part of this performance remains yet to be poticed in which the Author proposes a new lyftem,-new at Jeast at the time when this part of the work was composed, and even when it was sent to the press--on the combustion of badies, the cause of animal heat, and other subjects connected with them. Under great disadvantages, and by dint of specua
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 these 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 last theory, and of the experiments on which it is establifed, 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 theorist the reader will judge, from the following short account of it; so far as it tends to explain the theory of combuftion.
When an infiammable body, alcohol for inftance, is suffered to fame away; nothing but phlegm, an uninfiammable substance, can be collected from it. The alcohol 'therefore has been intirely decomposed; and its phlogiston, in particular, has been separaied 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 constituted it an inflammable substance.--Now, as the Aame, says the Author, continued only while the air was taking the phlogiston from the vapour, and went out when the air was no longer able to do this; it seems that the combustion depended intirely on such action of the air on the phlogiston.'
After observing that the combination of certain substances with each other is attended with heat; Mr. Elliot fuppofes that the heat generated in the combustion of bodies is occasioned by the phlogiston, contained in the inflammable body, combining with the air; or, to use his own words, that air has a greater affinity with phlogifton, than the substances have with which it is combined in inflammable bodies; and therefore when all circumstances properly concur, it astracts that principle from those bodies; that a shining heat is generated by their combination; and that this decompofition, when once fufficiently begun in a perfectly inflammable body, together with the shining heat which is a consequence thereof, will be continued on the principles above laid down, without any
farther affistance from extraneous lieat, as long as any of the subItance remains'
Even in close vessels, where there is no communication with the external air, combustion is nevertheless maintained, and that too with violence, if nitre be mixed with the combuftible body: because, says the Author, it is now well known that nitre, or the microus acid, contains a quantity of common air, or rather indeed of air itill more greedy of phlogiston, and therefore better adapted to promote combustion than common air, Jo the process of deflagration, the phlogiston, and tbis
air, dislodged from their respective bafes, suddenly rush into union, and produce a shining heat. : The Author illustrates this doctrine in various manners, and not without occasionally referring to some known experiments, from which he deduces consequences subversive of the prevailing theory relative to combustion ; particularly of that part of it which supposes that phlogiston is combined elementary fire, let loose, and rendered elaftic in that process, and that the heat and light of flame proceed from the ayolation of this disengaged principle. He acknowledges that the light proceeds from it, though the heat does not; and that the latter proceeds from disengaged fire, as chemists indeed at present imagine ; who are mistaken only with respect to the origin of that fire.
Hitherto the Author's hypothesis and that of Mr. Crawford nearly correspond, though the two 'Writers had no communication with each other. In what follows, the present Author proceeds further, and varies from his brother theorist, when he inquires into the origin of the fire above mentioned. For this he accounts by an hypotheis, principally founded on a variety of conjectures more or less probable, and inferences from a few experiments; with respect to the attractive and repulsive powers, and other qualities, of the particles of air, fire, phlogiston, earth, and æther not the chemical, but the hypothetical, puid fo called.
The Author next, in a more experimental manner, considers the phenomena of the light and colours exhibited by ignited ubs ftances; and then proceeds to apply some of the preceding observations respecting combustion, to respiration and animal heat (processes that bear a strong analogy to it), as well as to mufcular motion. But here we must refer the Reader, who has a taste for speculations of this kind, to the work itself for information. The Author has given a favourable specimen of his ingenuity, at least, in fabricating a system principally founded on fpeculation, that carries any face of consistency in it, with fuch delicate and difficult materials to work upon as those above -recited; the properties of some of which are not well ascer
tained, and the very existence 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 safe and sober mode of strict experimental investigation. It would be unfair, therefore, and invidious in us, to mark any defects that we may have observed in an ac. tempt of this kind, made by a person thus circumstanced. For the sake, however, of the Author, as well as of those who peruse his performance, we take a pleasure in complying with a request, which he has transmitted to us by letter, to convey to
the public the following additional observations, where he rectifies his own errors, and this we shall do in his own words.
« Since the book was published,' says Mr. Elliot, in his letter to us, I have, by a more attentive comparison of it with Mr. Crawtord's admirable discoveries, 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 existed in bodies only in its elastic state, as described in the first five cases of the seventh section. When air is heated and cooled, the phænomena seem to answer to that theory; and do not the expanfion of bodies, and the separation of their particles by heat, depend on the fame principle? Fixable air, however, is not much less elastic than common or dephlogisticated air ; though the former, by Mr. Crawford's experiments, contains 67, and the latter near 300 times more fire. Their specific gravities are to one another only as the nuinbers 281, 187, 185, or thereabout; and, consequently, the fire which is extricated by phlogiston was in a fixed or combined state. And, with regard to their elarricities, I have this to observe; that, as bodies which contain moft phlogiston refract light most strongly; so bodies which contain the greatest quantity of fire in a fixed state attract elastic fire most powerfully in the manner described in the cases above alluded to. But, as happens with the refraction of light, this difference will be but small, though the different proportions of fire in the bodies be very great, and only perhaps such as to answer to the numbers given above. The elasticity of air, the expansion of bodies by heat, and the separation of their particles, depend therefore on these principles;- the sensible heat, on the attraction of bodies for fire, or absolute heat, according to the law in Case untb, &c. and their absolute quantities of fire, on the quantity of phlogiston, 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 falls in the se cases; but, through not diftinguishing 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 present theorist; on account of the many marks of real ingenuity exhibited in this performance; particularly in the theory relating to combustion and respiration. His mcrit in this respect is the greater, as it evidently appears, from various pafl ages that occur in this work, that his necefl'ary avocations, and other circumstances, had not enabled him to know what had been done by others, or to make the necessary experiments himfelf. He is entitled to equal praise on' account of his unassumjag manner, and the great candour, and even warmth, with
which (in an Appendix written after his having feen Mr. Crawford's publication, while his own performance was at the press), he praises the work of a man, who, in point of time, had anticipated him in the publication of a capital discovery; and had thereby robbed him of a part, at least, of the glory which he expected to derive from it.
Such instances are rare among philosophers; and, in the present case, are sufficient to cover a greater muliitude of fins (against philosophy) than are to be met with in this perform
ART, VIIL Tbe Evidence of Realon in Proof of the Immortality of ibe
Soul, independent on the more abftrufe Inquiry into the Nature of Matter and Spirit. Collecied liom the Manulcripes of Mr. Baxter, Author of ihe Inquiry into che Na:ure of the huinan Soul, and of Matho, To which is prebixed, a Letter from the Editor to che Rev. Dr. Prieslev. Svo. 7 s. bound. Cadell.
1779. HOSE who are acquainted with, and admire, the meta
physical writings of the late Mr. Baxter, will think the world much obliged to Dr. Duncan for the present publication ; and for rescuing from oblivion the papers which he left behind him : in which he had collected together such proofs of the immortality of the human soul, as were independent on the metaphysical subtleties concerning its essence, its materiality or immateriality. In a prefatory letter, addreffed to Dr. Priestley by the editor, the latter gives an account of the circumstances by which he was enabled, and induced, to preserve these remains of a respectable writer, and to methodile and arrange them in such a manner as to render them fit for the inspection of the public.
Upon the rise of the late controversy concerning the materiality of the soul, Dr. Duncan conceived a desire of offering his sentiments on the subject. He wilhed, however, to see the public attention diverted from a metaphysical dispute, which, in the opinion of some, threatened great mischief to the moral world; though, in the judgment of others equally well in. tentioned, no prejudice was likely to ensue, either to religion or morals, from such a controverly; of which scarce one in twenty of those, who, at this day, pass for learned men, have ever properly considered the firft principles.'- In short, he studied to place in a clear and striking light, the arguments which natural reason fuggelts 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 observance of it; from the relation in which we stand to the Creator and Supreme Ruler of the universe; from his known perfections, in short, confidered respectively to the present state of his intelligent subjects upon earth.'