26 



NA TURE 



[November 5, 1908 



Mr. Bateman also pointed out that the twenty-four known 

 transformations of the hypergeometric equation into itself 

 arise naturally from the consideration of rotations in four- 

 dimensional space. 



Prof. Purser read a paper on motion of solids in an 

 incompressible fluid, and discussed the validity of the 

 application of Lagrange's equations of motion to such a 

 case. 



Prof. E. T. Whittaker, in a communication entitled 

 " The Extension of Optical Ideas to the General Electro- 

 magnetic Field," showed that the disturbances of the 

 Eether could be e.xpressed in terms of two functions, F, G, 

 as follows : — 



Electric vector 



o-F , a-G ?|T_^?2'£ fl5_if£GN 



Magnetic vector 



\ dydt ' 3a3s' dx\ 



\dydt 



dxdt'^dydz dt? fi di- j 



c being the velocity of light, and F, G solutions of 

 Laplace's equation of degree zero. Prof. Whittaker sug- 

 gested that these functions, F, G, might be taken as two 

 scalars defining the state of the aether in the same way 

 that temperature and pressure define the state of a gas. 



The general physics department on this day began with 

 a suggestion with regard to the meaning of valency, by 

 Mr. H. Bateman. In this paper the valency of an atom is 

 identified with the number of degrees of freedom of certain 

 displacements. A molecule has lost all these degrees. A 

 single atom or a cluster which still possesses " valency " 

 degrees of freedom may be regarded as an ion. A scheme 

 representing geometrically a sequence of processes which 

 possess some of the features exhibited by those taking 

 place within the atom was based on the theory of inversion. 

 A transformation of a specified type by inversion with 

 respect to two spheres was shown to depend on eight 

 parameters, a fact which may be of significance in regard 

 to eight being the maximum valency of an atom. Prof. 

 Rutherford congratulated the author, but pointed out that 

 it had not yet been shown that such a transformation by 

 inversion could take place physically. In response to a 

 question by the chairman (Prof. C. H. Lees), Mr. Bateman 

 stated that, for an atom such as he pictured, if the state 

 of motion is not steady the spectral lines would not be 

 sharp ; otherwise they would be sharp, .^fter any dis- 

 turbance the spectrum at first produced would be a con- 

 tinuous spectrum. 



Prof. J. A. McClelland followed with an important 

 summary of our present knowledge of secondary radiation. 

 It is unfortunate that it is not possible to further 

 summarise it in the few words available in these columns. 

 In the discussion. Prof. J. C. McClennan insisted that it 

 is necessary to determine the velocities and to employ the 

 magnetic field more before the various effects will be 

 disentangled. 



Then Prof. E. Rutherford gave the conclusions from 

 his recent experiments on the scintillations of zinc sulphide 

 (as in the spinthariscope). The effect he" believes to be 

 due, in the first place, to a chemical dissociation of the 

 sulphide, and the light is due either to this or to the 

 subsequent re-combination. Thus he dissociates himself 

 from the view that it is the result of merely mechanical 

 bombardment. He has measured the luminosity of the 

 sulphide screen when exposed to emanation from 200 milli- 

 grams of radium, and finds that 80 per cent, of the energy 

 of the a particles is transformed into light; about i/5oth 

 to i/iooth of a candle-power is obtainable. 



Mr. H. H. Poole described a determination of the rate 

 of evolution of heat by pitchblende. The experiment, 

 which seems to have been made with great care, gave 

 about twice the quantity estimated from the known amount 

 of radium present. Prof. Rutherford was of opinion that 

 possibly a small amount of chemical heating may be 

 present. 



Mr. T. Rovds, working in Prof. Rutherford's labora- 

 tory, described his measurements of the grating spectrum 

 of radiuni emanation. The error in the wave-lengths of 

 the grating photographs is not more than about o-i 

 Ang-strom unit. Prof. Dewar mentioned that the lines 

 published in Nature agree closely with lines given by 

 himself and Liveing obtained from less volatile con- 



NO. 2036, VOL. 79] 



stituents of air. The agreement was possibly accidental, 

 but it was well worthy of being tested. 



Photographs were next shown, by Dr. W. G. Duffield, of 

 the arc spectra of metals under pressure ; these include 

 those of iron and copper under pressures up to loi atmo- 

 spheres, and that of silver up to 121 atmospheres. 



Mr. H. Stansficld followed with a paper on secondary 

 effects in the echelon spectroscope. These effects arise 

 from repeated reflection from the plates, as in the Fabry 

 and Perot interferometer, and would, if alone, consist 

 of rings ; but . they are superposed upon the ordinary 

 echelon spectra. By raising one end of the echelon and 

 using screens, the secondary effects can be separated and 

 used alone. The resolving power is much greater than if 

 the secondary effects were absent. 



In the cosmical physics department a paper was read 

 by Dr. G. .\. Hcmsalech on new methods of obtaining 

 the spectra in flames. A special burner is fed with air, 

 which becomes laden with metallic vapour by passing 

 through a bulb containing a spark discharge. Investi- 

 gation of the iron spectrum showed that the lowest 

 temperature flame spectrum consisted of " enhanced " and 

 " polar " lines. Dr. W. G. Duffield welcomed Hcmsalech 

 and de Wattville's researches as overthrowing the 

 " temperature " hypothesis of the origin of " polar " lines. 

 Prof. Larmor indicated that the criterion for the produc- 

 tion of spectra was not temperature, but the acceleration 

 of the vibrating systems. Sir O. Lodge concurred. Dr. 

 James Barnes stated that he found that the 4481 Mg line 

 appeared as a polar line in the arc spectrum of that metal. 



Prof. J. Larmor then showed Dr. G. E. Hale's recent 

 photographs of the spectra of sun-spots taken through 

 polarising apparatus, in which the centres of some lines 

 are shifted relatively to their normal position, the direc- 

 tion of shift being changed by rotating the polariser 

 through 90° (see Nature and Astrophysical Journal, Sep- 

 tember). The effect is attributed to the magnetic field 

 arising from vortices of charged particles. The bearing 

 upon the phenomenon of the depth from which the light 

 was emitted was discussed. It is a pity that the pressure 

 of papers prevented a discussion on these important photo- 

 graphs from taking place. 



A paper by the Rev. A. L. Cortie, S.J., brought for- 

 ward evidence of the possible existence of steam in the 

 region of sun-spots. In a paper by Prof. Whittaker on 

 sun-spots and solar temperature, the possibility of the 

 existence of compounds in the sun was discussed, and it 

 was shown that pressure may be a more powerful agent 

 in preventing dissociation than temperature is in pro- 

 ducing it, and the characteristics of spot spectra may be 

 due to the high pressure. 



Mr. E. M. VVedderburn, in a paper on the causes of 

 seiches, brought forward evidence that their most effective 

 cause was a scries of atmospheric oscillations nearly 

 coincident in period with them. 



M. Teisserenc de Bort read a paper on the difference 

 of temperature of the upper atmosphere in polar and in 

 equatorial regions. At a height of 10 or 11 kilometres 

 there is no difference of temperature in the two regions. 

 Above this height, the arctic temperature keeps constant, 

 while the equatorial continues to decrease. Mr. W. A. 

 Harwood contributed a note on the ballon s-sondes ascents 

 made at Manchester during 1907-8, which confirm the 

 existence of the isothermal layer. 



Mr. J. S. Dines exhibited diagrams showing the results 

 of the hallons-sondes ascents made in the international 

 week, July 27 to August i, 1908. 



Captain H. G. Lyons gave the results of observations 

 of upper-air currents in Egypt and the Sudan. Mr. 

 R. G. K. Lempfert, of the Meteorological Office, exhibited 

 a zoetropic apparatus for showing the manner in which 

 cyclonic disturbances move across the British Isles, and 

 the way in which the air circulates. Mr. Paul Durandin 

 read a paper on an asymmetry in cyclones, in which he 

 pointed out that thunderstorms and tornadoes occur 

 generally on the right-hand side of the path of the centre 

 of the large depression with which they are associated. 



On Wednesday, .September 9, the section sat in single 

 session. 



Mr. T. L. Bennett rend, on behalf of Mr. J. I. Craig, 

 a paper on the changes of atmospheric density in storms. 



