Abstract
Poggendorff's Annalen, 1870, No. 8—The following are the contents of this number: (1) “Thermochemical Researches” (sixth, seventh, and eighth parts), by Julius Thomsen. This forms the conclusion of Thomsen's researches into the thermal effects of the neutralisation of acids, and ends with a collective statement of results. The experiments relating to what the author calls chemical “avidity” are likely seriously to modify commonly-received views of chemical action, showing as they do that the heat of combination between acids and bases is not a measure of their tendency to combine. (2.) “Researches relating to Electrical Discharge,” by W. von Bezold. Experiments relating to the propagation of sudden electric waves in branched conductors. The author finds, among other results, that the velocity of such waves is independent of the material of the conductor; his experiments also indicate the existence of electrical phenomena analogous to the reflexion and interference of waves. (3.) “On the Electro-motive Force of the Voltaic Arc,” by W. von Bezold. Edlund has shown that the electric light plays the part, not merely of a resistance interposed in the circuit, but also of an inverse electro-motive force. Von Bezold attempts an explanation of this fact, founded on the consideration that the discharge between the carbon-points must be periodic instead of continuous, and therefore their difference of tension a variable magnitude, whose maximum exceeds the electro-motive force corresponding to the resistance of the arc and the mean strength of the current. (4.) “On the Theory of the Electrophorus Machines and of the Supernumerary Conductors,” by P. Riess. (5.) “On the Specific Heat of Water in the neighbourhood of its maximum density,” by L. Pfaundler and H. Platter. The authors determined the specific heat of water between 0° and 11° C. by mixing weighed quantities at known temperatures between these limits, and observing the temperature of the mixture. From their results, they calculate an empirical formula containing the fourth power of the temperature. Taking the specific heat at 0° as 1, they find that at 1°.25 it is only 0.9512, while at 6°.75 it is 1.194, and at 11° it is again as low as 1.0298. (6.) “Acoustical Studies of Flames,” by E. Villari. The author found that the tone of a vibrating tuning-fork was reinforced when brought near to a large gas-flame. When the flame, which was thus thrown into sympathetic vibration, was looked at through radial slits in a rapidly revolving opaque disc, it was found that, if the rate of rotation of the disc bore the proper relation to the rate of vibration of the fork, the flame appeared to be divided by stationary bands showing alternate maxima and minima of brilliance. When the rate of vibration was changed, but all other circumstances remained unaltered, the distance between the bands was found to vary inversely as the rate of vibration. (7.) “On the ratio of transverse contraction to longitudinal extension,” by Heinrich Schneebeli. The author has applied Kundt's mode of measuring the length of stationary waves to the comparative measurement of the rates of the torsional and longitudinal vibrations of steel rods, and hence to the determination of the ratio between the transverse contraction and longitudinal extension produced by stretching forces: the mean results agree closely with those obtained by Kirchhoff and Okalow, as well as by Everett (Phil. Trans. 1867), from experiments on flexure and torsion. (8.) “On the compensation of an optical difference of path,” by J. L. Sirks. An investigation of the condition under which the interference tints produced by polarised light passed through a thin plate of crystal can be achromatised by a compensating plate of selenite. (9) “Rejoinder to Dr. Most,” by L. Boltzmann, relates to the second law of thermodynamics. (10.) “A contribution to the doctrine of Molecules and to the theory of Electricity,” by C. Lorenz. An attempt to calculate the absolute number of molecules in a milligramme of water, founded upon Weber and Kohlrausch's absolute measurement of the electro-chemical equivalent of water and on the difference of potentials required for its electrolysis. (11.) “A contribution to the theory of Terrestrial Temperature,” by O. Frölich. A discussion of Poisson's expression for the internal temperature of the earth at small depths below the surface, as a function of the time and the superficial temperature. (12.) “Remarks on the Bohemian Diamond,’” by Prof. V. L. von Zepharovich. The author states that only one diamond (not several, as has been implied in some reports) has been found in Bohemia; that this was discovered in a workshop in Dlasch-kowitz, where pyropes (garnets containing chromium) are ground and bored with the help of diamonds; and that it is not yet ascertained how it came to be among the pyrope-sand in which it was found. (13.) “A remarkable stroke of Lightning,” by Dr. J. G. Fischer. By examining the position of the magnetic poles in various pieces of iron and steel which were magnetised by the passage of the discharge, the author ascertained that the direction in which the negative electricity passed was downwards into the ground. (14.) “On the ratio of the specific heat of air at constant volume to its specific heat under constant pressure,” by Dr. Witte. The author concludes, on experimental and theoretical grounds, that this ratio is not constant, but is a function either of the temperature, or of the pressure, or of both. (15.) “On the minimum of prismatic deviation,” by A. Kurz. (16.) “An easy mode of preparing a liquid for the production of Plateau's Equilibrium-figures without weight,” by Rudolph Böttger.
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Scientific Serials . Nature 3, 216–217 (1871). https://doi.org/10.1038/003216a0
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DOI: https://doi.org/10.1038/003216a0
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