November 26, 19 14] 



NATURE 



353 



at Greenwich, provide a means of making a numer- 

 ical estimate of the amount of flattening. These 

 statistics extend so far as the seventeenth magnitude, 

 and are directly referred to standard photographic 

 magnitudes. Although magnitude-counts alone are 

 not suflicient to determine the general law of density 

 of distribution of the stars at different distances, yet 

 by comparing the counts in the galactic plane and 

 near the galactic poles the general shape of the sur- 

 faces of equal density can be found. The average 

 oblateness is about i : 35, that is to say, the same 

 falling off in density will be found 3^ times as far 

 away in directions in the galactic plane as at the 

 galactic poles. But the oblateness is not uniform; 

 at greater distances the surfaces of equal density are 

 less flattened; the number given refers to a distance 

 equal to the average distance of stars of about the 

 eleventh magnitude. This value of the oblateness is 

 considerably higher than was anticipated. The Milky 

 Way itself is not included in this estimate, and it 

 probably forms a flat girdle outside the oblate system 

 considered in the paper. 



The concluding sitting of the section on Tuesday 

 morning, August 25, attracted a very large attendance, 

 the room being filled to overflowing. Sir Oliver 

 Lodge opened a discussion on radio-telegraphy ; he 

 was followed by Mr. Balsillie, Prof. Howe, Dr. Eccles, 

 and others. The meeting was held jointly with 

 Section G (although, owing to their heavy programme, 

 that section was also meeting independently at the 

 same time), and an account of the discussion has 

 appeared in Nature under the proceedings of the 

 Engineering Section. The large attendance was a 

 tribute to the personality of the opener, but the subject 

 evidently appealed stro,ngIy to the general public ; 

 from the scientific point of view it was equally satis- 

 factory, and many points of great interest were 

 brought forward. 



After the discussion, Prof. Pollock gave an account 

 of some measurements of the wave-length in air of 

 electrical vibrations associated with a thin terminated 

 straight rod. 



Mr. Moseley read a paper on high-frequency spectra. 

 The references in the discussion on the structure of 

 the atom to the remarkable results derived from X-ray 

 spectra had aroused much interest ; and this fuller 

 account of his researches — postponed from a previous 

 day — was eagerly anticipated. He described the pro- 

 duction of the characteristic X-rays of the substance 

 by Kaye's method, and the measurement of their 

 wave-length by reflection of the image of a slit from 

 the surface of a crystal. The elements (from 

 aluminium to gold) were numbered in order with a 

 few gaps left for missing elements ; taking this atomic 

 number as ordinate and the square root of the X-ray 

 frequencies as abscissae, the resulting curves are prac- 

 tically straight lines. In most cases there are two 

 lines in the spectra, and the frequencies of the strong 

 component lie along one straight line in the diagram, 

 those of the w'eak components along another. It is 

 found (in order to preserve the continuity of the 

 straight lines) that a number must be left vacant for a 

 missing element of the manganese series between 

 molybdenum and ruthenium, and another between 

 tungsten and osmium. These gaps are also indicated 

 by Mendeleeff's table. Much confusion exists in the 

 rare earths as to how many separate elements exist, 

 and the method is able to throw light on this question ; 

 there is one element missing between neodymium and 

 samarium. A recent addition to the elements — celtium 

 — is not confirmed by this investigation ; the X-ray 

 spectrum indicates that it is a mixture of previously 

 known earths 



Prof. Porter read a paper by Mr. Paris and himself 

 on the scattering of light' by small and large particles 



NO. 2352, VOL. 94.] 



of conducting and non-conducting substances. Sus- 

 pended particles of sulphur, silver, and copper were 

 used, and the intensity and degree of polarisation of 

 the light scattered in different directions were 

 measured. For the metallic particles, the size could 

 be determined; the diameters in different experiments 

 ranged from 80 to 310 /i/x. From the direction of 

 maximum polarisation the conductivity of the particles- 

 could be measured. It appears that the conductivity 

 diminishes with the size of the particles ; and it is sug- 

 gested that the number of free electrons present in 

 the finely divided metal is smaller than when the 

 material is in mass. 



Dr. Rankine described methods of measuring the 

 viscosities of chlorine, bromine, and iodine at a num- 

 ber of different temperatures He discussed the rela- 

 tions between the viscosities of the three gases and 

 showed that they correspond with laws which he had 

 previously found to apply to the inert gases. 



During part of this final morning the department 

 of mathematics met separately, Prof. Carslaw pre- 

 siding. The following papers were read : — Mr. 

 Chaundy, " Symbolic Solution of Linear Partial 

 Differential Equations of the Second Order"; ProL 

 Fields, " Properties of Algebraic Numbers Analogous 

 to Certain Properties of Algebraic Functions " ; Prof. 

 Carslaw, "The Green's Function for the Equation 

 A^u-|-fe-« = o " ; Prof. Hudson, "The Evolute of the 

 Limagon " ; Mr. Macaulay, "The Algebraic Theory 

 of Modular Systems"; Mr. Macaulay, "A Property 

 of Double Points." 



Several papers were taken as read during the 

 different sittings. These included a number of local 

 papers, the authors of which were unable to attend. 

 Mr. Herens and Prof. Laby had a paper on an abso- 

 lute determination of the thermal conductivity of air; 

 Prof. Laby and Mr. Stuart on the nature of 7 rays; 

 Prof. Laby and Mr. Adams on the electric resistance 

 of steel tapes; Mr. Hogben, a map of the principal 

 earthquake centres of the south-west Pacific ; Mr. 

 Kidson on the general magnetic survey of Australia; 

 Prof. Laby and Mr. Herens on the thermal con- 

 ductivity of air ; Prof. Porter and Mr. Simeon on the 

 change of thermal conductivity during the liquefaction 

 of a metal ; Mr. Wellisch on experiments on the active 

 deposit of radium. These papers were all taken as 

 read. 



A brief reference must also be made to other activi- 

 ties of the section, outside the ordinary meetings for 

 papers and discussions. To meet the special circum- 

 stances of the Australian meeting an extra sitting of 

 the section was arranged at Brisbane, when Prof. 

 E. W. Brown delivered an address on the motion of 

 the moon. Evening discourses and public lectures on 

 physical and astronomical subjects were delivered 

 during the visit by Sir O. Lodge, Sir E. Rutherford, 

 Prof. Turner, Dr. Dyson, and Prof. Eddington. At 

 Sydney the local Astronomical and Mathematical 

 Societies held special meetings which many of the 

 visitors attended and took part in, and in more informal 

 ways the members found much scope for useful 

 activity outside the official programme. A sub- 

 committee, under the chairmanship of Prof. Love, 

 organised a series of experiments to be carried out 

 during the voyage to Australia, and a number of the 

 visiting physicists undertook to utilise the opportunity 

 in this way. No official information as to this work 

 is as yet to hand, but we understand that a good deal 

 was accomplished. Of special interest was Prof. 

 Duffield's investigation of the value of gravity at sea 

 by means of Hecker's apparatus ; the experiments 

 were carried out on the outward voyage on the 

 Ascanius, the owners (Alfred Holt and Co.) having 

 made very generous provision of facilities for the 

 work. 



