Abstract
Poggendorff's Annalen der Physik und Chimie, No. 2, 1876. —In the opening paper of this number Dr. König describes a series of researches in which he sought to study more closely the phenomena which occur when two sets of sound-waves meet in air; using sources of sound that were entirely isolated and could not act directly on each other, nor in common on a third body; he also chose sources that would give as simple tones as possible. The paper is in four parts, treating, severally, of primary beats and beat-tones, secondary beats and beat-tones, difference-tones and summation tones, and the nature of beats and their action, compared with the action of primary impulses. On the last head he finds, inter alia, that beat-tones cannot be explained by the cause of difference and summation tones, and that the audibility of beats depends only on the number and intensity of the primary tones, not at all on the width of the interval. The number of beats and primary impulses with which both may be perceived as separate impulses is the same; so, too, with the number at which beats and primary impulses pass into a tone. Intermittences of a tone, as well as beats and primary impulses, may pass into a tone, and the periodic maxima of vibration of a tone, when in sufficient number. The beat tone formed by two primary tones must be always weaker than these, though separate beats are stronger than the tones forming them.—In M. Grotrian's researches on the constants of friction of some salt solutions, and their relations to galvanic conductivity, the method for ascertaining the constants was that of observing the oscillations of a suspended disc with attached magnet (under the influence of a neighbouring magnet) in air and in the liquid examined. The observed generally similar course of temperature coefficients for fluidity and galvanic conductivity, with change of concentration, leads the author to conclude that the overcoming of internal friction forms an essential part of the work done by a current in passage through an electrolyte. In the case of chloride of potassium, it is found that the increase of conductivity is almost exactly proportional to the per-centage proportion (in the liquid); and M. Grotrian infers that the chemical changes he conceives generally to occur in chemical constitution of electrolytic molecules, on altering the concentration, do not occur here, but that with varied concentration, at the same temperature, the conductivity is only conditioned by the proportion of salt and the viscosity. With the numbers obtained in the experiments, it is possible to estimate for variously concentrated solutions of a salt, the temperatures for which the constants of friction have some determinate constant value; then to calculate the numbers for the conductivity at this temperature, and inquire according to what law these alter with the concentration. He thus shows that in the case of NaCl, KaCl, CaCl2, and BaCl2, the concentration and the viscosity are the principal factors which determine the amount of the conductivity.—In the next paper M. Wiedemann makes some adverse criticism on the recent researches of some French physicists in the domain of magnetism.—M. Holtz shows that wire-net is very well suited for proving that in the interior of conducting surfaces there is no electrostatic action. In one experiment, a bell-shaped cover, made of the net, is brought down by an insulating handle on an insulated metallic disc connected with an electric machine, and on which stands a pith-ball electrometer. The two balls do not diverge in the least on working the machine; but if the bell be removed, they do so at once. He shows further, how such a bell is like a filter or sieve, holding back the electricity while it affords partial passage to gaseous matter or dust. If a metallic point connected to earth be brought near the electrified bell, the balls are moved, but do not diverge, &c.—Dr. Wichmann studies the properties of doubly-retracting garnets; and we note a paper by Dr. Sohncke on the figures eaten out by dissolving liquids on blocks of rock salt, and Exner's method for producing solution-figures.—There is an account of an interesting inquiry, lately conducted by Dr. W. Siemens, on the velocity of propagation of electricity in suspended wires.
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Scientific Serials . Nature 14, 141–142 (1876). https://doi.org/10.1038/014141a0
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DOI: https://doi.org/10.1038/014141a0