servations on shooting stars. This work embraces all belonging to what are called meteors. The author is under great obligations to the French government who, on the recommendation of Arago, placed Mr. Coulvier Gravier in a situation to follow his tastes for this sort of observation. This observer does not despair of obtaining the means of predicting the meteoric periods. He unfolds his theory in a volume which all can understand, since it is written in a simple style and contains few mathematical formulæ. It shows that the author has obeyed a controlling taste; and his work fills an important gap in astronomical bibliography. Cours de Mecanique appliqueé par M. Mahistre. 1 vol. 8vo, illustré de 211 figures. Mr. Mahistre is professor of Mechanics a la Facultè des Sciences a Lille, one of the great manufacturing centers of Europe. His admirable work is especially adapted to engineers and to students who are destined to industrial pursuits. Cours de Mécanique appliquée par M. Bresse. T. 1.-Mr. Bresse is Professor of Mechanics at the celebrated Ecole des Ponts et Chaussées. This first volume treats specially of the strength of materials. Like the work of Mahistre, it is particularly adapted to civil engineers; above all it interests the engineers of bridges and roads, who in France occupy so important a rôle, particularly in railroad constructions. Multitudes of these engineers are found scattered over the continent of Europe, especially in Russia, Germany, Spain, Switzerland and Belgium. The science of the pupil gives evidence of the master, who is Mr. Bresse. Cours d'Electrophysiologie par M. Matteucci. 1 vol. 8vo.―This course pronounced at the University of Pisa is now reproduced in France where the well known high reputation of the author will secure it the attention it deserves. Cours d'Analyse de l'Ecole Polytechnique par M. Sturm. T. II, in 8vo, 1859. We have already announced the first volume of this great mathematician, who died some years ago. It is published by one of his pupils, Mr. Proutret, by the choice of the author, and from the manuscript left by him. This work is of special value to professional mathematicians, and to those who are charged with the instruction of this science. SCIENTIFIC INTELLIGENCE. I. CHEMISTRY AND PHYSICS. 1. On Torsion and its relations to Magnetism.-WIEDEMANN has communicated several interesting papers on torsion and its relations to magnetism, from the last of which we extract the following comparative view, referring to the original paper for the details of the experimental methods employed. Torsion. 1. The temporary torsions of a wire twisted for the first time by increasing weights, augment more rapidly than the weights. Magnetism. 1. The temporary magnetisms of a bar magnetized for the first time by increasing galvanic currents, augment more rapidly than the intensities of these currents. 2. The permanent torsions of the wire increase still more rapidly. 3. A much smaller force is necessary to untwist the wire than to twist it. 4. By repeated turnings of the wire, its torsions approximate more and more closely to a proportionality with the turning weights. The torsions are thereby greater than in the first turning. 5. By repeated application of the same twisting and untwisting weights, G. and G. the maximum of torsion reached in the turning, sinks, and the minimum reached in the detorsion of the same, rises up to a definite limit. 6. When twisted beyond the limits of the repeated torsions and detorsions the wire behaves as if it were twisted for the first time. 7. A twisted wire which is untwisted by the force -G cannot be twisted by repeated action of the force -G in a direction opposite to the first torsion. But the force +G twists it easily in the first direction. 8. When a wire which possesses the permanent twisting A is brought by the force b to the tor sion B and then farther to the torsion C, which lies between A and B we need the force b to give it again the torsion B. In this case, A may be also 0, and B may be greater or smaller than A. 9. Vibrations during the action of a twisting weight increase the torsion of a wire. 10. The permanent torsion of the wire after removing the twisting weight, is on the contrary, diminished by vibrations. 2. The permanent magnetisms of the rod increase still more rapidly. 3. A much weaker counter current is necessary to demagnetize the bar, than to magnetize it. 4. In a case of repeated magnetizations of the bar, its magnetisms approach more and more closely to a proportionality with the intensity of the magnetizing currents. The magnetisms are thereby greater than in the first magnetization. 5. By repeated application of the same magnetizing and demagnetizing currents, J. and J. the maximum of magnetism reached in the magnetization, sinks, and the minimum of the same reached in the demagnetization rises up to a certain limit. 6. When magnetized beyond the limits of the repeated magnetizations and demagnetizations, the bar behaves as if it were magnetized for the first time. 7. A magnetized bar which is demagnetized by a current of the intensity -J cannot be magnetized in a direction contrary to that of the first magnetization by repeated action of the current -J. But the current +J magnetizes it easily in the first direction. 8. When a bar which has the permanent magnetism A is brought by the current b to the magnetism B, and then farther to the magnetism C, which lies between A and B, we need the current b a second time in order to communicate again the magnetism B. In this case A may also be 0, and B may be greater or smaller than A. 9. Vibrations during the action of a magnetizing current, increase the magnetism of a bar. 10. The permanent magnetism of the bar after removing the magnetizing current is on the contrary, diminished by vibrations. SECOND SERIES, VOL. XXVIII, No. 84.-NOV., 1859. 11. A wire twisted and then untwisted loses or gains torsion by vibration according to the magnitude of the detorsion. 12. The permanent torsion of iron wires diminishes by their magnetization, and that in a ratio which diminishes as the magnetism in creases. 13. Repeated magnetizations in the same direction scarcely diminish the torsion of the wire. A magnetization in the opposite direction to the first produces however a new strong diminution of the torsion. 14. When a wire, by frequent magnetizations in opposite direc tions, is untwisted as far as possible by this process, it assumes by magnetization in one direction a maximum, by magnetization in the opposite direction a minimum of torsion. 15. A twisted wire which has been partially untwisted, loses by magnetization much less of its twist than an ordinary twisted wire. A wire farther untwisted, exhibits on feeble magnetization at first an increase of its torsion, which by augmenting the magnetization rises to a maximum and then again diminishes. The more strongly the wire was untwisted, the stronger must the magnetism be, in order to reach this maximum. When the wire is very strongly untwisted, its torsion increases, even up to the application of the strongest magnetization. 16. When a wire is magnetized while under the influence of the twisting weight, its torsion increases by weaker, diminishes by stronger magnetization. 17. A wire twisted at the ordinary temperature loses torsion by heating, and on cooling again recovers a portion of its loss. The changes increase with increasing torsion. After repeated changes of 11. A magnetised and then demagnetized bar loses or gains magnetism by vibration, according to the magnitude of the demagnetization. 12. The permanent magnetism of steel bars diminishes by their torsion and that in a ratio which diminishes as the torsion increases. 13. Repeated torsions in the same direction diminish the magnetism of a steel bar but little. A torsion in a direction opposite to the first, produces, however, a new strong diminution of the magnetism. 14. When a bar by repeated twisting and untwisting is demagnetized as far as this is possible by torsion within definite limits, it assumes a maximum of magnetism by torsion in one, and minimum by torsion in the opposite direction. 15. A magnetized bar which has been partially demagnetized, loses by torsion much less magnetism than an ordinary magnetized bar. A bar, which has been farther demagnetized, exhibits on feeble torsion, at first, an increase of magnetism which on increasing the torsion, rises to a maximum and then again diminishes. The more strongly the bar was demagnetized, the stronger must be the torsion to reach this maximum. When the bar is very strongly demagnetized the magnetization increases even up to the application of very strong torsions. 16. When a steel bar is twisted when under the influence of a magnetizing current, its magnetism increases by weaker, diminishes by stronger torsion. 17. A bar magnetized at the ordinary temperature, loses magnetism by heating, and on cooling recovers a portion of its loss. The changes are proportional to the magnetization. After repeated changes of temperature, the wire arrives at a constant state, in which to every temperature corresponds a definite torsion of the wire, which diminishes as this temperature increases. 18. A wire twisted at the ordinary temperature, and then partially untwisted, loses on heating so much the less of its torsion, the farther it has been untwisted. Upon cooling, its torsion is less than before if the detorsion has been slight, but greater if this has been considerable. 19. A wire twisted at a higher temperature, loses torsion on cooling. Upon a second heating, it again loses, and upon a second cooling first regains a portion of its loss. When the wire is vibrated previous to the first cooling, it immediately gains in torsion. temperature, the bar arrives at a constant state, in which to every temperature corresponds a definite magnetism of the bar, which diminishes as the temperature increases. 18. A bar magnetized at the or. dinary temperature, and then partially demagnetized, loses by heating so much the less of its magnetism the farther it has been demagnetized. On cooling, its magnetism is less than before when the demagnetization has been slight, but greater when this has been considerable. 19. A bar magnetized at a higher temperature loses magnetism on cooling. By a secong heating it again loses, and by a second cooling first regains a portion of its loss. If the bar is vibrated previous to the first cooling, it immediately gains in magnetism. From this comparison it will be seen that there is an analogy between the phenomena of magnetism and those of torsion, which holds good even in the details. The author remarks that this result is incompatible with the old assumption of the existence of magnetic fluids, but that we cannot justly infer from it, that the magnetism of a bar depends upon torsion. This is not proved by experiment; moreover as he proposes to show in another memoir, similar relations are found in the case of other molecular displacements, as for example, in flexion.-Pogg. Ann., cvi, p. 161. 2. On the densities of vapors at high temperatures.-H. SAINTE CLAIRE DEVILLE and TROOST have continued their investigations on the densities of vapors, employing the apparatus already described, but substituting the vapor of boiling cadmium (860° C.) or of zinc (1040° C.) for the vapors of mercury and sulphur, used in their former experiments. The vessels employed were of porcelain, instead of glass, and could be hermetically sealed by means of the compound blowpipe. To avoid the dif ficulties of a precise determination of the temperature, the authors always employed vessels of the same substance and of the same capacity, in which they enclosed successively vapor of iodine and the vapor of the body experimented upon. In this manner, the ratio of the densities of the two vapors was determined-the density of the vapor of iodine having been previously accurately determined. By this process the determination of the temperature becomes unnecessary. were as follows: The authors results Sulphur, at the temperature of 860° has a vapor density of 2.2, and this density does not change as the temperature rises, being the same at 1040° as determined by more than twelve experiments. We may there fore admit with certainty that the equivalent of sulphur (16) represents one volume of vapor, like oxygen (8). The vapor of selenium presents the same anomalies as the vapor of sulphur. At 860° its density is 82; at 1040° it is not more than 6:37. The authors propose to determine the density of this substance at still higher temperatures. The vapor density of phosphorus at 1040° is 45-1 vol., corresponding to the equivalent generally adopted. The vapor density of cadmium at 1040° is 3.94-2 vols. Calculated on this hypothesis it would be 3-87. At 1040° the vapor density of sal-ammoniac is 1·018 vols. (calculated 0.92.) The observed vapor density of bromid of aluminum is 18.62 2 vols. (calculated 1851). The vapor density of iodid of aluminum in like manner corresponds to 2 vols., and is 27.0 by observation; 27.8 by calculation. These two last numbers are calculated from experiments made in the vapor of sulphur. The iodid of aluminum exhibits a singular property indicating that its elements are united by a very feeble affinity. This iodid fuses at 125°, boils at 350°. At this temperature its vapor behaves as if it were composed of pure aluminum in a peculiar state of insulation; it burns in the air on contact with an ignited body, giving iodine and aluminum. It explodes by the electric spark when mixed with oxygen, in a strong vessel.-Comptes Rendus, xlix, p. 239. 3. On organic compounds which contain metals.-FRANKLAND has published a fourth memoir in continuation of his investigations of the compounds of metals with organic radicals. By the action of zinc-ethyl upon the iodid of stannethyl, the author obtained a crystalline compound of iodid of zinc and bi-ethyl-tin, having the formula Sn(C4H5)2+ZnI, the reaction being represented by the equation SnC4H6I+ZnC4H5 (Sn(C4H5)2+ZnI). When this compound is distilled, the distillate washed with water and again distilled, bi-ethyl-tin passes over as a clear colorless liquid, of a faint ethereal smell, and a somewhat metallic but not disagreeable taste. The density of its vapor is 8.021, which corresponds to 1 vol. of tin-vapor and 4 vols. of ethyl, the 5 being condensed to 2. It boils at 181° C. and distils over unchanged. It burns with a dark deep blue bordered flame giving off white vapors of oxyd of tin. Bi-ethyl-tin like zincethyl is not capable of uniting with any other element unless an equivalent of ethyl is separated at the same time. Iodine forms with it a compound having perhaps the formula Sn2(C4H5)21, though it may be the compound described by Cahours and Riche, Sn2(C4H5)31. (C4H5 { which he terms By the action of methyl-zinc upon iodid of stannethyl, Frankland obtained a colorless liquid having the formula Sn ethylo-methylide of tin, the vapor density of which also corresponds to 2 vols. C2H3 When zinc-ethyl is brought into contact with the iodid of methyl-mercury, Hg, iodid of zinc is separated after a few hours, and on distillation, bi-ethyl-mercury is obtained. This body agrees completely with |