The conciseness and experimental nature of the paper render it incapable of analysis: but we doubt not that it will be read with pleasure by the intelligent inquirer. ART. XIV. Experimental Essays, Political, Economical, and Philoso phical, By Benjamin Count of Rumford. Essay VII. Of the Manner in which Heat is propagated in Fluids; of a remarkable Law which has been found to obtain in the Condensation of Water by Cold when it is near the Temperature at which it freezes; and of the wonderful Effects which are produced by the Operation of that Law in the Economy of Nature. Together with Conjectures respecting the final Cause of the Saltness of the Sea. 8vo. Cadell jun. and Davies. 1797. 28. WI ITH the philosophical abilities and patriotic exertions of Count Rumford, the public are already well acquainted; and the present Essay will not be found at all derogatory from the fair fame of this accurate observer of the laws of Nature : who, more than any other philosopher since the days of Franklin, has applied his important discoveries to real use, and daily application in the service of domestic economy. We shall present our readers with a full analysis of these curious and interesting experiments; which, by their novelty and extensive application, rank the author with the Priestleys and Lavoisiers of the age. A few years ago, from various circumstances, the Count was led to suspect that water was an exception to the general rule of the ready and equable diffusion of heat through bodies; and accident having furnished him with the fact that, in the heating of liquids, two concentric currents were produced, moving in opposite directions, with a rapidity proportionate to the difference of temperature between the fluid and the surrounding atmosphere, he imagined that the motion in the several liquids, which were made the subjects of experiment, was caused by their particles going severally and in succession to give off their heat to the sides of the tube in which they were coutained, and therefore that these, and probably all other fluids, are non-conductors. This being the case, it was evident that, if by any means the internal motions could be retarded, the heat would be the more slowly propagated through the fluid. To verify this deduction, a thermometer was fixed in the axis of a hollow copper cylinder, and surrounded by the substances which were made the object of experiment: the cylinder thus charged, after being cooled down to 32° Fahrenheit, was plunged in water kept constantly boiling during the whole experiment, and the number of seconds accurately noted during the rise of the thermometer to a temperature equal to that of the surrounding hot hot water with the following results. When the cylinder was charged with pure water, of which it contained about 2470 grains, 597 seconds elapsed in the process of raising the thermometer from 32° to 200°. When 192 grains of Eider-down and 2276 grains of water were employed, 949 seconds were required. When to the same quantity of water were added. 192 grains of starch, 1109 seconds were required; and when stewed apples were used, 1096 seconds were required. The thermometer having become nearly stationary at 200°, the charged cylinder was taken out of the boiling water, and plunged into a mixture of ice and water; and the time which the heat from 200° to 40° took in passing out of the thermometer being noted, it was found to be, when surrounded by pure water 1032" by water and Eider-down 1541 1548 by stewed apples 1749 The fact being thus ascertained, that whatever impedes the internal motions (of fluids weakens their power of transmitting heat, the author proceeds to relate the following experiments. Having procured a large thermometer tube, with a bulb two inches in diameter, and a cylindrical neck of an inch in diameter, and twelve inches long, he put into it a quantity of coarsely pounded amber; filling up the tube with a dilute alkaline solution of exactly the same specific gravity as the amber, and closing its top with a cork. The instrument thus prepared, was plunged into boiling water, and instantly two currents in opposite directions began to move with great celerity in the liquor; the ascending current occupying the sides of the tube, and the descending, its axis:-as the liquor of the thermometer. grew warm, the velocity of the currents diminished, and entirely ceased when the temperatures of the hot water and thermome-. ter became equal. The thermometer being now taken out of the water and exposed to the cool air, the currents again became apparent: but their directions were reversed, that which occupied the axis being now the ascending current; and when the liquor in the tube became of the temperature of the surrounding air, these motions entirely ceased. A partial motion might be produced in any part of the tube, on the application. of any body either hotter or colder than the liquor; if the body applied was hotter than the tube, the motion of the liquor nearest to the hot body was upwards: if colder, downwards; and either of these currents being produced caused a contrary current in the opposite part of the fluid. If the middle of the tube was inclined over a flame, a rapid motion was observable in the upper part; while the liquor in the lower end and in the 13 bulb bulb had no perceptible motion. On continuing the heat, the fluid in the upper part could be made to boil, while that in the lower was not to the hand palpably warm. Reasoning from these facts, the Count concluded that the ice, floating on the surface of water, does not suffer the water to rise above 32°, and is readily melted on boiling water; yet, if the ice were fixed to the bottom, that the superincumbent water might be heated to any temperature; and even that boiling water standing above ice ought not to dissolve any of it. This deduc tion was submitted to the following experiments. Into a high cylindrical glass he poured 6 lb. 14 oz. of boiling hot water; and a cake of ice, 3 inches thick, weighing 10 oz. being put gently on it, was entirely melted in 2 min. 58 seconds. This experiment was repeated, the ice being fastened to the bottom of the jar; when, after two hours were elapsed, the water was poured off, and the ice on weighing it was found to have lost 5 oz. 6 grains; whence it appears that ice melts more than eighty times slower at the bottom of a mass of boiling water, than when suffered to swim on its surface. According to the theory, however, not a particle of the ice ought to have been melted: but this fact was satisfactorily explained by new experiments, and by the late discovery of M.de Luc and Sir Charles Blagden, that, though all bodies are condensed by cold, yet in regard to water there appears to be a very remarkable exception to this law; for, though water is con densed by cold at every descending degree of temperature which is considerably higher than that of freezing, yet its condensa tion does not go on till it is changed into ice: but when, in cooling, its temperature has reached to 40° Fahren. or eight degrees above freezing, it ceases to be farther condensed, and, on being cooled still farther, actually expands till it freezes; and, when become solid, it expands still more on growing colder. Now, as water in contact with melting ice is always at the temperature of 32°, it is evident that it must be specifically lighter than water at the temperature of 40°: the ice, there fore, which disappeared in the preceding experiments, was melted by the hot water after having been cooled down to 40°. Hence it follows that boiling hot water does not thaw more ice when standing quietly on its surface, than water at the temperature of 41°, or nine degrees only above freezing. This deduction being submitted to repeated experiments, and the results being averaged, it appeared that, when boiling water melted 150 grains of ice, an equal quantity of water at the temperature of 41°, in the same time and under the same circumstances, melted 189 grains. REV. Nov. 17972 Z The The general laws resulting from these grand discoveries,— namely, the non-conducting power of water with regard to heat, and its exception from that otherwise universal law of Nature, the unlimited condensation of bodies by cold,-are applied in the third Chapter to the satisfactory explanation of many important and curious facts in the process of congelation; and to some highly probable conjectures on the final cause of the saltness of the ocean, and the freshness of lakes and inland seas in high latitudes. These bring to a conclusion the present Essay; which, for accuracy of experiment and clearness of reasoning, well merits a distinguished rank among the philosophical treatises of the age. ART. XV. Padotrophia; or the Art of Nursing and Rearing Children. A Poem in Three Books. Translated from the Latin of Scevole de St. Marthe. With Medical and Historical Notes; with the Life of the Author, from the French of Michel and Niceron; his Epitaph, &c. &c. By H. W. Tytler, M.D. Translator of Callimachus. 8vo. pp. 400. 6s. Boards. Debrett, &c. 1797. IT T is to us a matter of serious regret, when we observe men of industry and ingenuity employing their talents in ways which cannot possibly conduce to obtain for them that return of reputation, nor of emolument, which they might justly expect from better-directed efforts. The task of translation is one of those in which this failure of judgment is most frequently made. All old works of established character having already undergone the process of naturalization, nothing is left but either to multiply versions,-probably with little chance of such a decided superiority as may engage the public attention,— or to hunt out some obscure originals, which their subject or other circumstances have doomed to neglect; and which, therefore, are little likely to become popular again in a translation. Of this last kind are many of the Latin poems which raised the reputation of scholars at the revival of literature, but which soon gave way to the works of the antients themselves, and to those of moderns who made a better application of their talents by writing masterpieces in their own language. As many of these scholars, too, had much more erudition than taste, and aimed at what was uncommon rather than what was beautiful, their choice of subjects was such as must infallibly, when the novelty was over, sink them into oblivion. Of this fault, we conceive, a more striking example can scarcely be given than the "Padotrophia" of Sammarthanus affords; for it is difficult to imagine any topic less fertile of the agreeable or elevated ideas of poetry, or more liable to excite images of disgust, than the detail of the nursery. As to the utility of such an attempt, a person must have extraordinary notions of the province and powers of verse, who would not prefer sober prose for any matter of scientific or technical instruction; and if, instead of reviving the work of St. Marthe, written two centuries ago, with all the errors and absurdities of the age, and by one who was not a medical man, Dr. T. had thought proper to create a didactic poem out of the writings of Smellie, Cadogan, and Underwood, we believe that he would even then have had few readers among midwives and nurses. We are far, however, from wishing to preclude a fair judgment of the merits of St. Marthe and his translator, by those who can interest themselves in the inquiry. Dr. T., we are sensible, has taken pains to render his translation as good as the subject will admit ; and though the long prefixed life of St. Marthe will not reflect great honour on the author's prose style, the following specimen may prove that the general strain of his verse is far from contemptible:-it is taken from a pleasing exhortation to mothers to perform the task of suckling their own children: • Spontaneous still the grateful liquor glides, And still the child sucks in the flowing tides, |