Abstract
Annalen der Physik and Chemie, No. 6.—In view of the considerable discrepancy between observation and theory with regard to the propagation of electricity, Herr Lorenz has been led to make fresh experiments (here described). In one method the telephone was used; the other was a modification of Feddersen's jar-discharge method. Herr Lorenz shows that, in the case of iron telegraph lines, the magnetism of the iron must be considered. The electro-dynamic constant of unit length of an overland telegraph wire is expressed by C = 2 log.½hα; + 2πk, where h denotes the height above the ground, π the radius of the wire, and k the function of magnetisation. For unmagnetic wires, the latter member falls away. Applying the formula to Fizeau and Gounelle's experiments, and putting the function of magnetisation of the iron wire = 10, we get the velocity 126000 km., while that observed was 101710 km. The difference is much less than by the ordinary reckoning, and may be attributed, the author thinks, to faults of insulation.—Studying the generation of the currents of a Gramme machine with regard to time and resistance, Herr Herwig finds, inter alia, that at the commencement a greater manifestation of force is obtained with greater resistances; but in later stages of development of the current, the force increases more for smaller resistances. The slow development of current with great resistances is shown by the fact that with 13.4 Siemens' units, the full force possible was not reached in four seconds.—Prof. Colley concludes from experiment, that the “polarisation of electrodes” in electrolytes is not to be attributed to dielectric polarisation of the latter, but deserves the name just given. It is not denied, however, that the dielectric polarisation may exist, being completely masked by the other.—Herr Settegaast makes some contributions to quantitative spectral analysis; his paper treating (1) of distribution of a base between chromic acid and other acids; (2) of quantitative mode of determination of nitric acid, and (3) of determination of phosphoric acid.—Among the remaining subjects handled, we note the angle of polarisation of fuchsin (Glan), application of the method of dimensions to proof of physical propositions (Neasen), and the heat-conduction of liquids with reference to currents arising from differences of temperature (Oberbeck).
Article PDF
Rights and permissions
About this article
Cite this article
Scientific Serials . Nature 20, 307–308 (1879). https://doi.org/10.1038/020307a0
Issue Date:
DOI: https://doi.org/10.1038/020307a0