Societies and Academies | Nature

ABSTRACT LONDON. Royal Society, May io.Sr J. J. Thomson, president, in the chair.Sir Joseph Larmor and N. Yamaga: Permanent periodicity in sun.spots. A discussion of the more sharply marked

phases of the curve of frequency of sun-spots, since 1750, led New- comb, in 1901, to strong confirmation of the prevalent view, previously verified by Wolf and by Wolfer, that sun-spots are

governed by some permanent periodic agency of period determined very closely by him as I I. 13 ± O02 years, and more recent independent dis. cussions, by Wolfer in 1902 and by Schuster in

1906, have led them to conclusions nearly identical. The form of this periodic component is here extracted by semi-graphical methods, such as are appropriate to a permanent unbroken period,

and also provide a further check on the degree of validity of the result. The periodic feature is found to be strongly and definitely present, provided the records for the two sun-spot

cycles from about 1776 to 17q8, which would largely vitiate it, are rejected as untrustworthy, or else are almost wholly assigned to some strong but transient anomaly. The residue of the

sun-spot curve, when this periodic part is removed, seems to be accidental and sporadic, showing no other permanent periodicity of comparable period. The periodogram analysis of Schuster

hail, in fact, already led him to the result that the record is not homogeneously con- stituted even in the wider sense appropriate to natural radiation. The Fourier series here determined

for the periodic part is found to be composed of sines only within the limits of attainable accuracy; thus the graph of that part is made up of anti-symmetrical undulations, a feature which

may form a clue to its physical origin in the sun.Prof. G. N. 0. Howe: The high-frequency resistance of multiple-stranded insulated wire. The conductors employed in radio- telegraphy are

frequently made up of a large number of fine wires separately insulated and stranded or plaited together in such a way that every wire occupies in turn the same telative position in the

multiple con- ductor. In this way the total current is forced to distribute itself equally between all the wires, even at high frequencies. The object of this is twofold, viz. to make the

inductance independent of frequency and to reduce the resistance at high frequencies. It is shown in this paper that the second object is rarely achieved because of the eddy currents induced

in the wires by the magnetic flux within the conductor. It is shown also that the loss due to this cause is so great that the effective resistance of the stranded conductor is. in many

cases, greater than that of the solid wire which could be put in its place.. In the first part of the paper formula are deduced on the assumption that the eddy currents in the fine wires do

not appreciably affect the distribution of magnetic flux within them. in the second part this assumption is not made and formuke are deduced which take into account the screening effect of

the eddy currents. It is proved, however, that the assumption is permissible in nearly all the cases considered. A number of tables are given showing the ratio of the high frequency to the

continuous current resists nces of straight and coiled conductors of different sizes made up of fine wires of three alternative diameters. These formulie and tables enable one to see at once

if any advantage is to be gained by using such a stranded conductor in any given case, and, if so, the best number of wires and space-factor to employ. The paper shows con- clusively,

however, that the extended use of such con- ductors in radio-telegraphy for the purpose of reducing the resistance has no scientific justification. Access through your institution Buy or

subscribe This is a preview of subscription content, access via your institution ACCESS OPTIONS Access through your institution Subscribe to this journal Receive 51 print issues and online

access $199.00 per year only $3.90 per issue Learn more Buy this article * Purchase on SpringerLink * Instant access to full article PDF Buy now Prices may be subject to local taxes which

are calculated during checkout ADDITIONAL ACCESS OPTIONS: * Log in * Learn about institutional subscriptions * Read our FAQs * Contact customer support RIGHTS AND PERMISSIONS Reprints and

permissions ABOUT THIS ARTICLE CITE THIS ARTICLE _Societies and Academies_ . _Nature_ 99, 258–260 (1917). https://doi.org/10.1038/099258a0 Download citation * Issue Date: 24 May 1917 * DOI:

https://doi.org/10.1038/099258a0 SHARE THIS ARTICLE Anyone you share the following link with will be able to read this content: Get shareable link Sorry, a shareable link is not currently

available for this article. Copy to clipboard Provided by the Springer Nature SharedIt content-sharing initiative