clined to afcribe to them. Of this, however, his readers will judge for themselves. For our part, we own we are dull enough not to perceive the great utility, or indeed the novelty, of the last mentioned doctrine; on which the Author feems to lay fo much ftrefs- that the elements act on one another?-Granted: and what then? In the fourth and fifth difcourfes, the Author treats of fire, and of air. In the first of thefe, he defcribes and gives a drawing of a pyrometrical machine, or apparatus conftructed by him, for afcertaining the expanfion of bodies by heat. By means of this inftrument, the flame of a farthing candle was found to be of fufficient force to lift a weight of 500 pounds. But to afcertain the highest degrees of heat, the Author employed the expedient of plunging a ftrongly heated body, a piece of iron for inftance, into a given quantity of mercury; and then calculated by the heat which the mercury was found to have acquired; what must have been the original heat of the immerfed body? According to a fcale of heat, deduced from the Author's experiments and calculations, and adjufted to Fahrenheit's fcale, mercury is fuppofed to freeze at 350 below o: fpirit of wine, at 52°, likewife below o tin is found to melt at 490°; oil of vitriol boils at 546 lead melts at 610: mercury boils at 700: iron juft red hot, in the dark, 1000°; by day light, 1120°; iron with a heat almoft white, 2080°; in fufion, 3000°, and upwards. The inquifitive Reader will however undoubtedly with that the Author had defcribed his mode of operating with more minutenefs, that he might be enabled to form fome judgment with respect to the accuracy of thefe numbers. = In afcertaining the degree of the white sparkling heat of iron, at a fmith's forge, and which was found 2,80°, a very fingular phenomenon prefented itfelf. It was very remarkable, fays the Author, that when the iron had been plunged with fo great an heat into the cold mercury, it contracted a thin but hard and durable coat of [quick] filver. Iron being the only metal to which mercury will not adhere, it has been the cufiom to fuppofe fome repulfion or natural antipathy between their parts: but thefe appearances are all over-ruled by the different degrees of heat and cold. In the hands of fome practical chemift or mechanic, this fact of the confolidation of quickfilver, might poffibly lead to fome new and ufeful application of that wonderful fluid. The method of confolidating it, feems to depend upon communicating to it the highest poffible heat, and at the fame time preventing its evaporation.'-This feeming amalgamation of mercury with iron certainly deferves to be further inquired into. In the next difcourfe on Air, the Author-(to use his own phrafe, which, we confefs, gives us not even the fhadow of an idea), confiders air and fire as different conditions of the fame elementary matter of the heavens." We meet with no motives to induce us to dwell long upon this difcourfe; in which the Author likewife fpeaks of fixed air, and elastic vapours ;' such as nitrous, inflammable, foul air, &c. Our philofophical Readers will be content with a very fhort paffage extracted from this part of the difcourfe: We may therefore fay of all thefe factitious airs, that they are nothing but ether combined with expandible matter. So many conjectures have been formed on experiments of this kind, with fo many tranfitions from natural air to artificial, and from artificial to natural, that M. Lavoifier, who reviewed them in the flate they then were, obferved, with fome reafon, that the fubject was in great perplexity.'-How far the Author's ether and expandible matter' are likely to clear up this perplexity; or what idea these two terms, thus united, are defigned to convey, we pretend not even to guess. In the next difcourfe, On the philofophy of mufical founds,' among many other matters well known to the mufical theorist, the Author prefents him with a few others that have the merit of novelty. Treating of temperament, and of the famous mufical comma, a fubject which we had lately occafion to difcufs very particularly *-he obferves that that little comma would afford a man work enough for his life;-and I apprehend he would find it untractable to the laft.' On this occafion, the Author prefents his Readers with the fubftance of fome manufcript papers of the late Mr. Davis, who had attempted to reduce the whole fyftem of keyed inftruments to an equal temperament. It appears, nevertheless, that Mr. Davis had been anticipated in this fcheme by fome former theorifts, and even by Father Merfenne. On the whole, the Author is rather perfuaded that a variety, in the tones and femitones, is not only neceffary to fatisfy the proportions of the fcale; but that even the extreme and lefs tuneable keys have their beauties, and affift the effect of the more perfect ones. A mufical Reader may, however, be curious to try the effect of this equality, and to compare it with the common methods. And for thorough-bafs in a concert, a harpfichord might anfwer better when tuned by this rule, than by any other.' Treating of Tartini's third founds, on which we offered fome conjectures feveral years ago, the Author gives us a folution of the difficulty, propofed to him by a learned friend, the Rev. Mr. Twining; which he confiders as the true one. We fhall give See our laft Review. + See M. REVIEW, vol. 45. November 1771, page 371; and December, page 477• it it in the Author's own words; referring our mufical Readers, for an explanation of the fubject, to the articles in our journal above alluded to. • Suppose the two notes that are founded are the fifteenth and the feventeenth; their vibrations coincide at every fifth pulfe of the upper note, and at every fourth pulse of the lower note: and when they conspire, the vibrations of each become more intenfe, fo as to be diftinguifhed by the ear. But their coincidence happens exactly at the fame intervals with the vibrations of the fundamental note, or unifon; and thence the unifon is heard as the third found. The lower tone would hit the unifon at every fourth vibration; the higher would hit the unifon at every fifth vibration. Now let the unifon be removed, and they meet each other where each would meet the unifon; and then the fenfation of the unifon is excited. Whether there is a third fphere of undulations, produced in the air by the concurrence of the other two, is a question of fome difficulty; but without fuppofing it, the effect must be referred rather to the imagination than the fenfes.' In this difcourfe, the Author gives a well-authenticated account of the invention, or rather perhaps the re-invention, of the Eolian barp, by the late Mr. Ofwald. To account for the production of the different tones in this aerial mufic, he fuppofes that air, like light, confifts of heterogeneous parts differently refrangible; and that as colours are produced by inflexions and refractions of the rays of light; fo mufical founds are produced by fimilar refractions of the air: the air, in fhort, becoming vocal, by a kind of refraction occafioned by its paffing over the edge of an aperture; juft as light prefents us with colours, not only by paffing through a prifm, but alfo by moving over the edge of a folid body. This whimsical theory has no other foundation than the wellknown, and, probably, merely accidental, analogy between the fpaces occupied by the feven colours in the folar spectrum, and the feven intervals which denote the tones and femitones of the octave, in the fcale of mufic; or rather in a fcale which is not now in ufe. The Author however goes further, and perceives an analogy between three of the feven colours, viz. red, yellow, and blue, which he confiders as fimple and primary; and the three principal tones which conftitute the harmony of the octave, viz. the unifon, the third, and the fifth. For our part, we can fee no reafon to fuppofe, that any thing happens, in the refraction or infection of light, that can juftly be faid to refemble any effects produced by the mere change of direction, which a current of air fuffers in paffing through a narrow paffage, or over the edge of a body. In this laft cafe, its inflexions are fuch as are common to any elaftic fluid, moving in in fimilar circumftances. We doubt not but that, under the fame circumstances, mufical tones would be produced by fixed or phlogisticated air, or even by the elafic vapour of water, from an colopile: but we fhould not fufpect that any of these fluids would be decompounded, merely by their inflection, or change of courfe. The analogy too between the folar Spectrum, and the mufical octave, evidently fails, when we confider that a ray of light is not only actually decompounded by a prism; but that the decompofition is permanent, and the parts remain feparate: whereas, even granting that the air may confift of heterogeneous particics of different magnitudes, &c.; neither the nitrous, or any other teft of the integrity or purity of air, has yet exhibited to our modern experimental philofophers any figns, or even induced any fufpicion, that that fluid is liable to be decompounded by a mufical inftrument, or an air-prifm, as the Author terms the Eolian harp-Were we to attribute to the air, thus fuppofed to be affected, the qualities ufually afcribed to air decompounded, we fhould be ready to apprehend, that an Eolian harp, placed at a window, would probably confume as much air as a lighted candle; and that huge air prijm,' the organ, would, if played upon, refract, and decompound as much air in an hour, as might ferve for the confumption of a moderate family for a whole week. We should not overlook a practical improvement of the Eolian harp, which is defcribed, and has been executed by the Author. -inftead of fixing the ftrings to the outfide,' fays the Author, I difpofe them upon a founding board or belly within fide a wooden cafe, and admit the wind to them through a horizontal aperture; fo that the affinity of the inftrument to an organpipe appears at firft fight: and thus it becomes portable, and ufeful any where in the open air, inftead of being confined to the house; which is a great advantage; and it is probable this new form may lead to fome new experiments.' We have not yet noticed thofe parts of the prefent Work, in which the Author takes occafion to combine natural and experimental philofophy with philology, theology, &c. Treating of the uses and application of mufic, the Author makes his orthodoxy at leaft confpicuous, by citing, with complacency, a paflage from Symfon's Chelys; in which that writer, defcanting on the three fundamental notes of the octave-the unifon, third, and fifth-confiders them as affording us "a fignificant emblem of that fupreme and incomprehenfible THREE in ONE, governing, comprifing, and difpofing the whole machine of the world, with all its included parts, in a moft perfect and ftupendous harmony." This phyfical trinity,' adds the Author, as an abfolute fact in mufic, must be evident to every beginner in the science; and it is a trinity in unity: but it is a mirror, in which many eyes will difcern no image: -With me it is a matter of fmall fmall concern, how fuch an allufion would be relished by a Middleton, a Bayle, or a Voltaire, whofe minds were poisoned by a difaffection to truth, &c. &c.' In the 7th and 8th difcourfes, the Author treats of foffil bodies, with fome obfervations introductory to a theory of the earth;' and on phyfical geography, or the natural hiftory of the earth.' Thofe who wish to acquire a knowledge of the principal marine fhells, and other animal and vegetable matters found in the bowels of the earth, will here meet with descriptions of feveral fubjects, illuftrated with plates; together with reflections concerning the origin of marine foils. The volume is terminated by a difcourfe on the appearances, caufes, and prognoftic figns of the weather.' ART. II. Two Letters to Dr. Newcome, Bishop of Waterford, on the 178.. English Harmony of the Evangelifts; and our Readers will find an account of it in our Review of that publication. It is here reprinted, that the whole correspondence might be before the Reader in a more convenient form.' To this letter Dr. Newcome publifhed an aufwer, in which, agreeably to Dr. Priestley's wifhes, his Lordship entered into a particular confideration of the fubject, ftated the facts and circumftances upon which his opinion refpecting the duration of our Lord's miniftry was founded, and made obfervations upon fome of the principal arguments which the Doctor had alleged in favour of Mr. Mann's hypothefis. We gave our Readers an account of his Lordship's publication in the Review for June laft. The fecond letter before us is in reply to Dr. Newcome. Dr. Priestley begins with expreffing the pleafure it gives him to find his Lordship enter fo fully into the difcuffion of the subject, and his hope that fome new light may be thrown upon it, even though it should not be decided to general fatisfaction. He next apologizes to the Bifhop for not making a reply fooner, declares the high refpect that he entertains for him, and affures him, that he esteems it an honour to difcufs a queftion fo interefting to many Chriftian critics, and which has never been properly difcuffed before, with a perfon of his Lordship's learning and candour. And then, after a few curfory reflections on the incidental advantages attending fcriptural inquiries, he obferves, that, in order to introduce as much diftinétnels as poffible into the conduct of the argument, and to render it lefs tire Review for February, 1731, p. 84. 2 fome |