Scientific Serials

Abstract

Wiedemann's Annalen der Physik und Chemie, No. 11.—Experimental researches on the origin of frictional electricity, by C. Christiansen. Friction by itself does not generate electricity. The appearance of the latter is due to chemical decompositions which are initiated by contact and completed on separation. These results are those of experiments with a tube coated on the inside with various insulators, arranged so that mercury could be brought into contact with them and withdrawn, after which a charge was indicated by a galvanometer.—On thermocouples of metals and saline solutions, by August Hagenbach. In the case of couples consisting of inetals and their salts, the E.M.F. increases with the dilution, and more rapidly than the difference of temperature. In combinations of platinum with hot and cold saline solutions the same acids give about the same forces, and differences of concentration have a very marked influence. The highest E.M.F. obtained was that of a platinum-cupric-chloride couple, which, with a 5˙6 per cent, solution, and with the two communicating portions of the liquid at 25° and 80° respectively, gave an E.M.F. of 0˙1541 volts.—Changes of length produced by magnetisation in iron, nickel, and cobalt ellipsoids, by H. Nagaoka. The optical lever method was employed. As the field intensity increases, iron first expands and then contracts, going through the opposite stages on reversing, and showing a decided hysteresis. Nickel simply contracts. Cobalt contracts first and then expands, the expansion increasing to a limiting value as the field intensity increases.—On elliptically-polarised rays of electric force, and on electric resonance, by L. Zehnder. The author shows how to produce circularly and elliptically polarised electric rays by two wire gratings placed one behind the other, with the directions of wires crossed.—On refraction and dispersion of rays of electric force, by A. Garbasso and E. Aschkinass. To produce a prism capable of affecting ether waves of the length of those due to Hertzian oscillations, a prism was constructed of a series of parallel glass plates, upon which were stuck “resonators” made of strips of tinfoil. This was placed between an exciter and a suitable resonator. It was found that the rays were refracted by angles differing according to the wave-length. The deviations for three different resonators were 9° 6′, 7° 18′, and 5° 24′ respectively.