June 20, 1901] 



NA TURE 



199 



Physical Society, June 14. — Prof. S. P. Thompson, F.R.S , 

 president, in the chair. — A paper on Herr Jahn's measurements 

 of the electromotive force of concentration cells was read by 

 Dr. Lehfeldt. Prof. D. Jahn has recently published measure- 

 ments of E.M.F.'s of concentration cells, from which he has 

 endeavoured to show that the law of dilution is applicable to 

 strong solutions. The author points out that his conclusions 

 are based on argument in a circle because Ostwald's law is 

 assumed in the formula used by Jahn for calculating degrees of 

 concentration. The formula; of Nernst and Arrhenius do not 

 yield consistent results, and it is suggested that the former is 

 suitable for calculating concentrations and the latter for calcu- 

 lating osmotic pressures. — A paper on the mechanism of radia- 

 tion was read by Mr. J. H. Jeans. This paper contains an 

 attempt to obtain answers to two questions : — (i) What infer- 

 ences can be drawn as to the mechanism by which radiation is 

 emitted from an examination of the formula of physical optics ? 

 and (2) Is it possible, with the help of these inferences, to 

 frame any conception of matter which will give a consistent 

 account of the various optical phenomena ? Starting with general 

 spectroscopy, the author has written down the r.adiation due to 

 a single rotating molecule vibrating harmonically. The effect 

 of a number of molecules is deduced, and it is shown that the 

 condition that the continuous banded spectrum shall be absent 

 is that either the period of rotation must be large compared with 

 the period of vibration or the radiation from a molecule must 

 be spherically symmetrical. Passing on to dispersion, even if 

 the radiation is continuous between collisions, there will be a 

 discontinuity at every collision and the train of waves will be no 

 longer regular. It is customary to assume that the vibrations 

 of a dispersing medium are sympathetic with the irregular 

 incident light. The author has calculated the ratio between 

 forced and free vibrations in a prism or grating, and finds that if 

 the dispersion is to be regular the vibrations m.ust be only 

 slightly influenced by collisions, and this requires, as in the 

 former case, that either the period of rotation is large compared 

 with the period of vibration, or the radiation is spherically 

 symmetrical. As this is not the case with molecules the author 

 thinks that the line spectrum is emitted by atoms, that these 

 atoms must be dissociated and that the shape of these atoms is 

 one of spherical symmetry. It is shown that if an atom is an 

 electromagnetic system, similar to a planetary system, then the 

 periods of such an atom would not be fixed and there would Ije 

 no reason for a line spectrum. The normal atom is therefore 

 regarded as an electrostatic system, with some law of force, 

 other than the inverse square law, holding at interionic dis- 

 tances. Such an atom when at rest would give a pure line 

 spectrum. Rotation of such an atom causes the lines of the 

 spectrum to shift towards the red, and as the rotation is different 

 for different atoms the lines will not only be shifted, but 

 broadened. To calculate the periods of vibration of an atom 

 the author has assumed it to consist of an infinitely great number 

 of infinitely small ions. The spectrum of this consists of a 

 collection of spectrum series each possessing a definite head and 

 capable of explaining doublets, triplets, &c. It is shown that 

 under the action of a magnetic field a line may separate out into 

 approximately equidistant lines, the central lines maintaining 

 its position. In conclusion, the author points to many other 

 physical phenomena which can be explained by the theory 

 described.— The chairman then exhibited some specimens of 

 Jena glass. In describing these, reference was made to a diagram 

 showing the refractive index, dispersion between the C and F 

 lines, and the reciprocal of the dispersive power of any piece of 

 glass. For this latter quantity the symbol " v " is used, and it 

 was suggested to call it the achromatic refractivity of the glass. 

 The introduction of barium increases the deviation, but leaves 

 the dispersion unaltered. It is possible now to get crown glass 

 with a higher refractive index than flint glass, and this makes it 

 possible to construct an achromatic lens which will also give a 

 flat field. It is usual in making achromatic objectives to make 

 them accurately achromatic for the red and violet rays. A better 

 effect can be obtained by having approximate achromatism 

 throughout the length of the spectrum. This is achieved by 

 matching the irrationality of one glass by means of another and 

 then constructing an achromatic pair with these two glasses. 

 "Telescope crown" and "telescope flint" are two glasses 

 which give similar spectra and approximate achromatism from 

 the red to the violet. — The Society then adjourned until Tune 

 28, when the meeting will be held, by the invitation of Prof. 

 \V. C".. Adams, in the laboratory of King's College. 



NO. 165 1, VOL. 64] 



Geological Society, Junes.— Mr. ,T- .T- H. Teall, V.P.R.S., 

 president, in the chair. — On the passage of a seam of coal into a 

 seam of dolomite, by Aubrey Strahan. The author was informed 

 by Mr. N. R. Griffith in 1900 that the seven-feet seam of the 

 Wirral Colliery had been found to pass into stone of an unusual 

 character. For a distance of 1600 yards from the shaft this 

 seam was good, and about 4 feet thick. A little farther in 

 bands of stone from i to 10 inches thick made their appearance in 

 it, and, gradually increasing in thickness, these bands eventually 

 constituted the whole seam, the last traces of workable coal dis- 

 appearing at 250 yards from the point where the change first 

 began. The boundary of the barren area has been found for a 

 distance of 1480 yards, and it runs north and south. The stone 

 is at first black, but after weathering it becomes grey, and dis- 

 plays curious structures, among which are pisolitic, or mammil- 

 lated structures, the intervening spaces being filled with coaly 

 matter. One specimen displays woody tissue filled with dolo- 

 mite. Analyses by Dr. W. Pollard yield from 18-5 to 13 per 

 cent, of magnesia. The phenomena are not those ot a " wash- 

 out," as there is no sign of erosion, but there is proof that the 

 dolomite was formed in almost motionless water, and the condi- 

 tions appear to have been those under which a tufa would form. 

 It appears to have been formed on a spot to which clastic 

 material scarcely gained access, and which was reached even by 

 vegetable matter in scant quantity and in a finely divided con- 

 dition. — On some landslips in boulder-clay near Scarborough, 

 by Horace W. Monckton. 



Edinburgh. 



Royal Society, June 3. — Dr. Hepburn in the chair. — 

 In a paper on binary fission in the life-history of Ciliata, 

 Dr. |. Y. Simpson gave excerpts from statistics of two months' 

 cultures of Paranioeciuni caudatuin showing that under the most 

 natural circumstances attainable binary fission does not proceed 

 with that mechanical regularity that Maupas asserted. Further, 

 experimenting with cultures of Styiossichia ptisttilata, he 

 found with Joukowsky as against Maupas that degeneration after 

 continued division shows itself in a general listlessness, in ebbing 

 of vital energy and decrease of size, rather than in definite nuclear 

 disorganisation, but on the other hand, with Maupas as against 

 Joukowsky, that it is not possible to induce conjugation before 

 puberty. Some Paramcecium monstrosities were described, and 

 microphotographs of living P. aztrelia and P. caudaliim were 

 shown, establishing the existence of the two species which had 

 recently been called in question. — Dr. E. G. Coker communicated 

 a paper in which were described his various forms of apparatus 

 for measuring strain and applying stress, together with a great 

 many measurements made by means of them. The aim in all 

 was to have the different parts of the measuring apparatus at- 

 tached to the specimen itself ; and probably the most ingenious 

 arrangement was the device for applying and measuring the 

 effects of combined bending and twisting. Another com- 

 bination was longitudinal stretch and twist. The influence of 

 the one kind of strain upon the elastic relations of the other kind 

 were carefully investigated, especially in the neighbourhood of 

 the yield-point. The behaviour of iron and steel bars when sub- 

 jected to strain cycles was also studied, and other important 

 questions connected with hysteresis, fatigue and recovery in 

 time. — Mr. W. E. CoUinge communicated a paper on the 

 anatomy of a collection of slugs from North-west Borneo, the 

 general results being as follows. The Damayanlia pkcia of 

 Issel was re-described and some notes given on the anatomy of 

 the new species, D. carinata. Two new genera were estab- 

 lished, viz., Wiegmannia and Isselentia, with five new species. 

 The Damayantia smii/it {CWge. and Godw., Auct. ) was shown 

 on anatomical grounds to belong to the genus Collingia. Finally 

 two new species of Veronicella and one of Onchidium were 

 described, and a check list of the known species from Borneo 

 was given. 



Paris. 



Academy of Sciences, June 10. — M. Fouque in the chair. 

 —Studies in neutralisation. On the titration of acids and 

 alkalis of complex function with the aid of colouring matters, by 

 M. Berthelot. A study of the behaviour of some amino-acids 

 towards indicators. Of these glycocoll and leucine are acid to 

 phenolphthalein, alkaline to methyl-orange, and neutral to 

 litmus. The three aminobenzoic acids have a clearly acid 

 function except towards methyl-orange. — The phenomena of 



