that by this the capacity is enlarged; and that from this, again, a quantity of caloric is abforbed, and becomes latent. What other cause is to alter the capacity? Not furely the specific combination of a portion of caloric; for this would be a modification of Dr Black's theory; and the question would recur, what determines this combination? The cause must be affumed to be that change in the conftitution of the body-in the arrangement of its particles which accompanies fluidity. And this change of capacity, when it does happen, muft neceffarily be immediately attended with an abforption of caloric, and muft therefore be regarded as its caufe. The three events are no doubt, to our observation, fimultaneous; but they are not actually fo: the one must momentarily, at leaft, precede the other; or, on the oppofite fuppofition, we shall have no distinct view of the difference in the theories of Irvine and Black. ་ Dr Irvine does not appear, indeed, to be very well fatisfied with this view of his father's doctrine; and he endeavours to fhew that the objection may be otherwife obviated. Various powers, he conceives, may operate, the operation of which we cannot eafily trace; fuch as electricity, magnetism, and galvanifm and fomething ought to be allowed for fuch circumftances, when we reafon concerning the action of particles among each other.' p. 65. This reafoning the opponents of the fyftem he defends will not, we are afraid, regard as fatisfactory, and we conceive it to be altogether unneceflary. Did our limits admit of the difcuffion, we believe that it would not be difficult to fhew that the change must be ascribed to the operation of fenfible caloric alone; that it is the refult of its accumulating expanfive power counteracting the cohesive attraction; that this change must happen at an indivisible point in the thermometrical fcale; and that there is no force in this objection to Dr Irvine's system. It has fometimes been faid, that the view which Dr Irvine gives of these phenomena is ultimately the fame with that given. by Dr Black. Dr Black himself was fenfible that it was not, and that Dr Irvine's theory was oppofed to his. The fame general fact, indeed, is admitted in both, or rather it is this fact for which they profefs to account. A quantity of caloric is absorbed during liquefaction and vaporifation, without producing increase of temperature; but the caufe affigned for this is very different in the one theory from what it is in the other. Dr Black always regarded this as existing in the fluid or vapour in fome peculiar state different from that portion of caloric which produces temperature, and which he denominated fenfible heat. Dr Irvine confidered it as not in the leaft different, as to its mode of exiftence, from the reft of the caloric which the body contains, or from that which VOL. VIII. NO. 15. K is is contained in others. In confequence of the change of form, that body is capable of containing more caloric than it could do, while in its former ftate, at the fame temperature, or requires more to produce a given temperature; and the caloric it abforks, goes merely with the caloric it formerly contained, to preferve the temperature at which the change of form happened. Dr Black confidered the change in the relation of the body to caloric as limited to the moment of liquefaction. Dr Irvine conceived the idea that it was not thus limited, but that this new relation was henceforward poffeffed by the fluid, and that in all fubfequent elevations of temperature, the body, in this form, abforbs more caloric than it did while in the folid ftate. The two theories, therefore, whatever may be their merits, are totally diftinct. We have been told, too, that Dr Black's theory is fimply the expreffion of the fact; that it is a plain doctrine, which, to be difputed, must be mifunderstood. It would be fo, if it merely announced, that when a folid becomes liquid, or a liquid is converted into vapour, a quantity of caloric is absorbed, which does not produce augmentation of temperature. But when it is affirmed that this portion of heat is the caufe of fluidity, and is united with the body in fome peculiar mode, to which its latent ftate is owing, it becomes an hypothefis, in oppofition to which the theory of Irvine may be fairly oppofed. Of their comparative merits, we believe few will doubt who examine them with attention. Dr Black's may appear conformable to fome loose analogies drawn from chemical combination. The other, independent of its experimental proof, is more fimple and more conformable to the laws which caloric, in its relations to bodies, obferves. To Dr Black will remain the honour of having difcovered and established, by a feries of admirable experiments, the general fact, that when bodies become liquid or aeriform, they abforb portions of caloric which do not augment their temperature; and to Dr Irvine, if we miftake not, will belong the praise of having given the juft theoretical view of this important phenomenon. We confider the fcience as indebted to the editor for having brought the fubject fully before the attention of chemists; and we have little doubt that he will have the fatisfaction of having contributed to establish his father's fame. Another interesting subject connected with Dr Irvine's theory, it is known, engaged the attention of that philofopher-the determination of the real zero or point at which the fcale of temperature commences, or at which bodies would be deprived of ca-* loric. At what distance from a given temperature, suppose that of freezing water, will this be found? It will be obvious to thofe who know any thing of the doctrines of heat, that such an actual actual reduction of temperature as would reach this point is impracticable; and it must therefore, if the folution of the problem is to be attempted, be determined by calculation. Dr Irvine was led, by the views his theory fuggefted, to the invention of a method of afcertaining the natural zero or point of total privation of heat, this method being founded on the confideration of the change of the capacity of bodies during their fufion, and of the quantity of caloric neceffary to produce fluidity.' It is fully ftated (p. 116.) from a manufcript of Dr Irvine's, which, from its length, we cannot infert. We can only observe, that it refts on the affumption that the quantity of caloric contained in bodies is proportioned to their capacity. If, therefore, the difference in the capacity of a body in its different states, for example, in those of folidity and fluidity, be determined, and if the quantity of caloric which it has absorbed or given out in the change of ftate be afcertained, we difcover, by a fimple calculation, the quantity of caloric it contains, and confequently the point in the thermometrical scale at which it would be deprived of caloric,⚫ the quantity being equal to the capacity of the solid multiplied, by the latent heat, and divided by the difference of the capacities. may likewife be determined by the comparison of the capacities of any two bodies which unite chemically before and after mixture, combined with the observation of the heat_given out at the same time.' From experiments in both modes, Dr Irvine fixed the zero at 900 below o of Fahrenheit. We cannot enter on the fubject more fully, but may merely remark, that although the principle on which the folution of the problem is attempted is probably juft, there are so many fources of error in the estimation of the capacities, and even in determining the quantities of heat evolved or absorbed, that we cannot place much confidence in the results, and accordingly these have differed widely as obtained by different experimenters. This has been afcribed to a radical fault in the method itself, while, on the other hand, it has been contended, that it may arife from the errors to which the methods of fixing the grounds of the calculation are liable; a position which Dr Irvine junior has, we think, fucceeded in establishing. It We have entered fo fully into the confideration of the first, and undoubtedly the most interesting part of this volume, that we can scarcely offer any obfervations on the remaining parts. The fecond is compofed of effays written by Dr Irvine, and feveral of them read before the Literary Society of Glafgow. As the production of a man of talents and celebrity they must excite interest ; but, independent of this, we have found in them fome original views, and a number of curious and important facts, which we acknowledge, from confidering the state of chemistry at the K 2 time time they were written, we did not expect. The first unfolds the principle on which the evolution of heat from chemical combina tion depends, and which Dr Crawford afterwards fo fuccefsfully applied to the explanation of the origin of animal temperature, and of the heat produced in combuftion. Among the others, w would particularly diftinguish the effays on the feeds and roots plants and on foils, and thofe on fermentation. In the former v have views of the circumftances connected with the growth, n trition, and propagation of vegetables, of the nature of foils, the caufes of their fertility, the changes they fuffer by cultivation, and their adaptation to particular plants, which, even now, with the aid of modern chemistry, could not perhaps be much improve, and which the naturalift and the fcientific agriculturist will per with pleafure. In the latter there are fome practical details a the procefs of fermentation, and the fubftances fufceptible of i and fome facts and principles ftated which we have been taught to believe were of more recent difcovery. In an effay on the quantity of matter in bodies, we have a very good sketch of the chemical views which immediately preceded the theory of Lavoifier, and fome ftriking experiments on the increase of weight in metal hic folutions. The laft part of the work confifts of two effays by Dr Irvin junior; one on latent heat, in which are related a series of exper ments on the quantities of caloric which become latent in the fu fion of fulphur, and of feveral of the metals, and which have added fome facts to thofe before known; and another on the affecti ons of fulphur with caloric, directed principally to the investigation of the fingular property which that fubftanee exhibits of thicken ing after its fution, by an elevation of temperature within a cer tain extent. ART. XI. Nathan the Wife: a Dramatic Poem. Written origi nally in German. By G. E. Lething. 8vo. pp. 293. Lon don. 1805. and W met with this volume by accident, a fhort time ago, have been fo much edified by its perufal, that we haften to give our readers an account of it. It is a genuine German drama, written without any imitation of French or English, and admirably calculated to elucidate the gative and peculiar tafte of that ingenious people. They have borrowed to much of late from both thefe quarters, that it may scalonably be doubted, whether a relilh for their own original and and appropriate literature be altogether fo common in this country as is usually imagined. This book, we think, will afford a very useful teft for determining that important problem, and will enable the reader immediately to afcertain whether he has hitherto admired the true German genius itself, or only its imitation of French and English. A traveller may very erroneously fuppofe that he relishes German cookery, when he gormandizes on fricandeau or plum-pudding at Vienna; but if he take delight in four krout and wild-boar venifon, he may reft affured that he is under no mistake as to the proficiency he has made, and that he has completely reconciled himself to the national tafte of his entertainers. The work before us is as genuine four krout as ever perfumed a feaft in Weftphalia. The ftory, in point of abfurdity, we think, is fairly entitled to bear away the palm from the celebrated German play in the poetry of the Antijacobin: the moral is no lefs comfortable; and the diction, though not altogether fo lofty, is, upon the whole, entitled to equal admiration, The scene is laid in Jerufalem in the time of the crufades; and the story turns chiefly upon the adventures of a young Templar, who had been made captive by the armies of the celebrated Saladin. This monarch, who is reprefented as a pattern of mild-, ness and generosity, chufes to amuse himself one morning by feeing the heads of twenty prifoners ftruck off by his chief executioner, and witneffes the operation upon nineteen of them with fingular complacency and fatisfaction. Being ftruck, however, with a fort of resemblance which the twentieth feemed to bear to a favourite brother, who had difappeared many years before, he directs his life to be fpared, and allows him to roam at large, in a ftarving condition, through all the streets of Jerufalem. In one of his evening rambles, this youth perceives the house of Nathan the Jew to be on fire; 3ntly going ance of the city firemen, is the means of delivering the Jew's daughter from the flames. The young Ifraelite very naturally falls in love with her preferver; but he, having a bad opinion of the whole nation, keeps out of the way of her gratitude, till Nathan finds him out, and wins the affection of this Chriftian champion in a moment, by affuring him that he is not a Jew, but only a fort of Deift, who has acquired a habit of going to the fynagogue without meaning any thing. The Templar protests that he is himself of the very fame faith; and, after vowing eternal friendship, he goes home with him and falls furiously in love with the daughter. In the mean time, Saladin fends for the Jew to lend him money, and to ask him which of the three religions is the beft, K 3 the |