490 



NATURE 



[December 9, 1920 



first 100 families in the world have island endemic 

 fjenera in 92, the genera being 129 per cent, of the 

 total genera in the families. The intermediate 

 92 families are represented by 45 only, with 928 per 

 cent, of their genera, and the last 100 by 13, with 

 872 per cent. 



Edinburgh. 

 Royal Society, November 22. — Sir Alfred Ewing, 

 vice-president, in the chair. — Prof. \V. Peddie : 

 Fechner's law and the self-luminosity of the eye. 

 This law states that the change of visual perceptivity 

 is proportional to the fractional change in the inten- 

 sity of the light. At weak intensities a term, regarded 

 as constant, has to be added to the intensity of the 

 •external light on account of the self-luminosity of the 

 eye. By integration over the whole stimulated part 

 of the retina Helmholtz obtained an expression for 

 the perceptivity which agreed with observation in so 

 far as the general nature of the relation between 

 perceptivity and external stimulus is concerned. 

 There was, however, a measurable difference for a 

 certain range of intensities. A close correspondence 

 can be obtained by assuming that the self-luminosity 

 term in Fechner's expression is itself a simple func- 

 tion of the external stimulus, rising' rapidly to a 

 maximum, and thereafter slowly falling to a steady 

 ■\alue. — Dr. H. S. Allen : /Ether and the quantum 

 theory. Although some supporters of the principle 

 of relativity reject the idea of aether, most physicists 

 still employ the aether conception in describing elec- 

 tric and magnetic phenomena. Certain classes of 

 physical facts appear to contradict the laws of classical 

 mechanics, and the quantum theory has been de- 

 veloped bv Planck and others to meet such cases. 

 It is argued in' this paper that the quantum 

 theorv necessitates the physical existence of lines 

 or tubes of magnetic force as discrete entities, 

 and yields a quantitative estimate of what must 

 be the fundamental unit magnetic tube. This unit 

 magnetic tube is determined bv the ratio of Planck's 

 constant, ]i, to the charge, c, of an electron, and is 

 equal to 4-12X10-' c.g.s. units. Consequently, one 

 c.g.s. line (one maxwell) contains 243 x to" "quan- 

 tum tubes." On this theorv aether mav be regardpd 

 as an assemblage of lines of force in accordance with 

 the representation given long ago bv Faradav and 

 Maxwell. 



Paris. 

 Academy of Sciences, November 15. — M. Henri 

 Deslandres in the chair. — C. Moureu and A. Lepape : 

 The rare gases in natural gases of Alsace-Lorraine. 

 The natural gases examined included five from 

 petroleum wells of Pechelbronn, one from the Wit- 

 telsheim potash mines, one firedamp from the Sarre- 

 et-Moselle coal mines, and two from mineral springs 

 (Niederbronn and Soulzmatt). The carbon dioxide, 

 oxygen, combustible gases, and nitrogen (including 

 rare gases) were determined and then the nitrogen 

 Avas analysed separately. The rare gases were separated 

 into two groups : arg'on with traces of krvpton and 

 xenon, and helium with traces of neon. The argon- 

 nitrogen ratios found varied, only between 091 and 

 248, but the helium-nitrogen ratios varied much 

 more widely, 238 to 26. — P. Thiodoridis : The thermal 

 variation of the coefficient of magnetisation of some 

 anhydrous chlorides and an oxide in the solid state : 

 the mag'neton theory. Measurements were made on the 

 anhydrous chlorides of cobalt, manganese, and nickel 

 and on manganous oxide at temperatures rancinsr 

 between 0° C. and .i;^o° C. For the chlorides of nickel 

 and cobalt the results conform to the magneton 

 theorv. but this is not the case for the determinations 

 with manganese chloride and oxide. — R. de Malle- 



NO. 2667, VOL. 106] 



mann : The rotatory power of tartaric and malic acids 

 in solution. Study of the variations in rotatory power 

 produced bv the addition of benzene to alcoholic solu- 

 tions of tartaric acid; the rotations are to the left for 

 all colours, and the dispersion is normal. In aqueous 

 solution this acid reverses its rotation in presence of 

 calcium chloride, and the dispersion, at first abnormal, 

 becomes normal after a certain quantity of the salt 

 has been added. Malic acid resenibles tartaric acid 

 and shows similar variations, but in the inverse sense. 

 — E. Darmois : The dispersion of the refraction of 

 hydrocarbons. If n and n' are the refractive indices 

 of a given hydrocarbon for two colours, the difference 



"-^, where d is the density, is called the specific 



disi^ersion. For different classes of hydrocarbons the 

 diherences in the specific dispersion are sufficiently 

 great to be of service in the analysis of mixtures such 

 as occur in petrols. — A. Holland : The micro-chemical 

 reactions of iodic acid. A description of the crystals 

 obtained with iodic acid and salts of thallium, silver, 

 barium, strontium, calcium, and rubidium. --P. 

 Fleury : The catalytic decomposition of an alkaline 

 solution of sodium hypobromite by copper sul- 

 phate. The opposing action of iodine. The 

 decomposition of the hypobromite solutions was 

 measured by the amounts of oxygen evolved in "i, 2, 

 and 4 days'. As Jittle as 0-25 milligram of copper 

 per litre of solution, was found to exert a marked 

 catalytic action. This effect can be completely 

 counteracted by adding small quantities of iodine. — 

 C. Dufraisse : The ethylene isomerism of the mono- 

 bromostyrolenes in the' lateral chain.— P. H. Fritel ; 

 The presence of the genera Gangamopteris and 

 Schizoneuta in the grits of Ankazomanga (south of 

 Madagascar). The presence of these plants indicates 

 a lower level of the Permian in Madagascar than that 

 recognised by M. Boule in the Sakamena Valley.— 

 G. Bertrand :' Observations on the properties of tear- 

 producing substances and the measurement of their 

 activity. Comments on the method used by MM. 

 Dufraisse and Bongrand in a recent communication 

 on the same subject. There are difficulties in the 

 exact definition of the limiting concentration produc- 

 ing effects on the eyes ; moreover, the sensibility of 

 the observer varies with the time of day. The mode 

 of attack by the different irritating substances is not 

 the same in all cases; chloropicrin, for example, acts 

 suddenly, whilst the effect of other substances, of 

 which monochloroacetone is an example, is progres- 

 sive. .\. Bach and Mme. Sophie Zoubkoff : Contribu- 

 tion to the study of the indices of the blood enzymes. 

 The estimation of catalase, peroxydase, and etherase 

 in one drop of blood.— E. Kayser : The influence of 

 luminous radiations on a nitrogen fixer. Cultures of 

 Azohacier ag'.le were grown under shades of coloured 

 glass and the nitrogen was assimilated by the bacteria 

 determined. The maximum nitrogen assimilation 

 was under yellow and green light. — J. Y. Heymans : 

 In vivo, as in vitro, micro-organisms pass through 

 the walls of a filter.— L. Leger : The endogenous 

 multiplication of Chloromyxiim triiiiae. 



Rome. 

 Reale Accademia dei Lincei, June 4. — A. Roiti, vice- 

 president, in the chair.— S. Pincherle : Iterated func- 

 tion of a rational integral one. — G. Fano. : Surfaces 

 of the 4th order w^ith infinite discontinuous groups of 

 birational transformations, i. The author commences 

 this series of papers with the F/4 containing two 

 slcew lines, the first example of the complete study 

 of a group for which Sever! 's quadratic form is 

 ternary. — G. Ciamician and C. -Ravenna: Considera- 

 tions regarding the function of alkaloids in plants. — 



