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NJmURE 



[May 5, 1921 



evolution. A cylinder of statocyte tissue is always 

 developed in the ground tissue of the young rachis, 

 which disappears at about the time of unfolding of 

 the leaflets, when response to gravity also ceases. In 

 Asplenium bulbiferum a curve showing the amount of 

 statocyte tissue present corresponds more closely with 

 the curve of geotropism. Growth continues some 

 time after the simultaneous loss of the statolith 

 apparatus and the power of gravitational response. 



April 28. — Prof. C. S. Sherrington, president, in the 

 chair. — Prof. H. Lamb and R. V. Southwell : The 

 vibrations of a spinning disc. This investigation was 

 suggested by the occasional failure of the blades 

 of steam turbines, apparently resulting from flexural 

 vibrations of the turbine disc. Expressions have been 

 obtained for the gravest natural frequencies of vibra- 

 tion (i) by exact methods, on the assumption that the 

 disc is so thin or rotates so fast that the restoring' 

 effects of centrifugal force are predominant and the 

 effects of flexural rigidity negligible ; (2) from Kirch- 

 hoff's theory for flat circular plates, in cases for which 

 the opposite assumption can be made ; and (3) by 

 Rayleigh's approximate method, employing an assumed 

 curve of deflection, for cases in which both centrifugal 

 and flexural effects require to be taken into account. 

 Employing method (3), the gravest natural frequency 

 of vibration must be over-estimated. It is shown 

 that a corresponding- lower limit can be obtained by 

 considering each restoring system separately. — Dr. W. 

 Rosenhain : The hardness of solid solutions. It is 

 suggested , that crystals of a solid solution of metal B 

 in-, metal A are built up on a single space-lattice 

 system similar to that of crystals of pure A, but that 

 certain atoms of A are replaced by atoms of B. As 

 th^ atoms of B are necessarily dissimilar from atoms 

 of:A,;thisi involves a certain amount of distortion of 

 the space-lattice, the amount of which will depend 

 upon the degree of dissimilarity between the two kinds 

 of atoms. The mechanical properties of the crystals 

 will be affected by the distortion, surfaces which were 

 plane glidings surfaces in the crystals of pure A being 

 n,o longer- perfectly plane in the "solid solution crystals, 

 and consequently offering an increased resistance to 

 slip within the crystal. The greater the distortion 

 produced by the introduction of an atom of B, the 

 greater will be the hardening effect of the introduction 

 of B into A in the form of solid solution. As a first 

 approximation, the hardening effect of one metal upon 

 another \h solid solution is inverselv proportional to 

 the splubility of ,that metal in the firs't. This is shown 

 to be in accordance with fact in regard to the alloys 

 of many metals. — W. Hartree and Prof. A. V. Hill : 

 A rnethod of analysing galvanometer records. The 

 naotjon of a galvanometer connected to a thermopile 

 in, contact with a body producing- or absorbing heat 

 is governed by linear differential equations with con- 

 stant coefficients. From the relation between galvano- 

 meter deflection and time the relation between heat- 

 production and time can be determined. It is neces- 

 sary to construot' a vcontrol -eui^vei"-i.e, the relation 

 between galvanometer deflection and time for an 

 mstahtaneou's liberation of heat in the bodv on th^ 

 t|iermbpile. The observed curve is recdnstfucted in 

 terms of the control curve, and, ' employing a 

 numerital method described, a fair analysis ' of the 

 course of the production or absorption of heal can be 

 mad°.— F. H. Newman : ;A new form- of Wehnelt 

 Interrupter/ /The -new interrupter: consist^ of a 

 platinum, wire immersed in a saturated solution of 

 afwmortimti jphosphate. The whole is contatned in an 

 ?lyiBi»JWjWjsi?e§s4,,,jV!^hicK,acts as the. cathod?,'. -Th^ 

 current density at the anode is- one^quart6r . of the 

 t4]>#':>'".thfe: Old fdrm-of Wehnelt interrupter ; con- 



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sequently there is less heating of the electrolyte and 

 less disintegration of the platinum wire. The inter- 

 rupter can be used with alternating currents, which it 

 rectifies. The secondary discharge, obtained from the 

 new type of interrupter, is very disruptive, and has a 

 large peak value. There is no self-induction in the 

 circuit when used with alternating currents. The 

 primary current wave-form has been investigated with 

 direct and alternating currents. — T. L. Ibbs-: Some 

 experiments on thermal diffusion. The method 

 depends on the use of the katharometer as an instru- 

 ment for accurate gas analysis. A temperature 

 gradient was applied to a number of mixtures of 

 hydrogen and carbon dioxide by passing them through 

 a cylindrical glass tube down the middle of which 

 was a platinum helix heated by an electric current. A 

 steady flow of the gas mixture was maintained, and 

 the gases were drawn off from the hot and cold regions 

 of the tube, afterwards passing through a differential 

 katharometer for analysis. There was a general ten- 

 dency for the hydrogen to diffuse towards the hotter 

 region and the carbon dioxide towards the cooler 

 region, confirming the results of Chapman and Doot- 

 son. Curves are drawn .showing that the amount of 

 separation is proportional to logTi/T^, where T, and 

 Tj are the absolute temperatures of the hot and cold 

 regions. The maximum separation for a given tem- 

 perature gradient is obtained in mixtures containing 

 from 50-60 per cent, by volume of hydrogen. The 

 results give strong support to the theorv worked out 

 by Chapman in his kinetic theory of gases. The 

 amount of separation is less than would be expected 

 if gas molecules behaved like rigid elastic spheres. — 

 B, N. Chakravarty : The diffraction of light incident 

 at nearly the critical angle on the boundary between 

 two media. 



Association of Economic Biologists, April 22. — Sir 

 David Prain in the chair. ^ — W. A. Millard : Green- 

 plant matter as a "decoy" for Actinoniyces scabies 

 in the soil. . The work of Gillespie, Hurst, and 

 Martin was criticised and the obligate relation of 

 potato-scab to a certain, range of hydrogen-ion values 

 disproved. Experiments carried out during several 

 years at Leeds were described and interpreted in. terms 

 of the author's "decoy" theory. — E. H. Richards: 

 The action of bacteria and protozoa in conserving the 

 nitrogen in sewage. A brief account was given of 

 the activated-sludge process by which intense aerobic 

 treatment increases the . nitrogen content from 2 per 

 cent, to from 5 to 7^ per t^ent,, the whole of this 

 bein^- derived .from the urea ,in the. initial sewage. 

 Estimating the weight of dry niatter in protpzoa and 

 bacteria at 25. per eenti, the author's experiments .at 

 the , J[^othamsted Experimental Station showed that 

 tljeriitrogen contained in these organisms gave 8 per 

 cent., a rernarkably dose approximation to the in- 

 creased nitrogen after activating sewage. Rotham- 

 sted .experiments were described which illustrated, the 

 valuable rnanurial properties of .activated sludge. — 

 G. P. Wiltshire • TJie methods of infection of the 



i apple e^qker fungus. .The parasite enters apple-trees 

 tjirough wounds caused by various natural and arti- 

 ficial agents, but the primary channel pf invasion is 

 through small cracks in the leaf-scars. The course 

 of such infection was described in relation to the 

 relative susiceptibilities of different varieties of apple. 

 The discovery of leaf-scar infection modifies ideas as 

 to th,e treatment of apple canUer, and. possible control 

 rr\€3"sui:es were considered, ,.. -;•, • 



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Academy of Sciences, April 11.--M. Georges Lemoine 



I in thef thklr.-v^P. Appefl : The periddiltil Movement of 



i £^ fltifai-^B.* Baillatad ; ' Ob.*fvatJons of the ^tat 



