Abstract
LONDON. Physical Society, June 25.—Sir W. H. Bragg, president, in the chair.—Dr. J. H. Vincent: The origin of the elements. The atomic weights are regarded as the weighted mean vtlues of the atomic weights of the isotopes of the elements; but it is assumed that, as a rule, the atomic weight is near that of some one isotope. Figures tnd tables are drawn up showing how this accounts for the values of a large number of atomic weights, if one also assumes that the weights and positions in the periodic table of any isotope are conditioned by laws similar to those holding in the recognised radioactive families. The elements are all supposed to be derived from parent elements by processes known to occur in actively radiating families, but their radioactivity is not, in general, detectable by the usual means owing to the velocity of expulsion of the particles being low. The possibility of the reversibility of some radioactive pro cesses is regarded favourably. The various difficulties in connection with the views advocated are discussed, and some suggestions for experiments made. Finally, the theory is used to explain the socalled laws of the atomic weights of elements of low atomic weight, and the shape of the curve obtained when the atomic weights are plotted against Moseleys numbers.—W. H. Wilson and Miss T. D. Epps: The construction of thermocouples by electrodepoition. The method, which was devised to overcome the difficulty of making satisfactory soldered joints between the elements of thermopiles having a large number of closely packed junctions, consists in using a continuous wire of one of the elements and coating those parts of it which have to form the other element with an electrolytic deposit of another metal. If the conductivity of the latter is considerably greater than that of the former, and a fairly thick sheath is deposited, a thermocouple is produced which is not appreciably impaired in efficiency by the shortcircuiting effect of the core. Constantan wires coated with either copper or silver sheaths were found to be suitable for most purposes.—J. Guild: The use of vacuum arcs for interferometry. The paper discusses the relative merits of short and long mercury arcs for this work, and points out that the defect of the former is due to the broadening of the spectrum lines consequent on the high vapour pressure within the lamp. It is shown that by attaching a condensing bulb to the lamp, so as to prevent exoessive rise of vapour pressure, the short lamp can be made practically as good as the long one as regards sharpness of lines, while still being of much greater intrinsic brightness.—S. Butter worth: The maintenance of a vibrating system by means of a triode valve. This paper gives a mathematical analysis of the arrangement, previously described by Eccles, whereby the vibrations of a tuningfork are maintained by means of a triode.
Article PDF
Rights and permissions
About this article
Cite this article
Societies and Academies. Nature 105, 842–844 (1920). https://doi.org/10.1038/105842a0
Issue Date:
DOI: https://doi.org/10.1038/105842a0