364 



NATURE 



[June 5, 19 1, 



the matter beyond doubt. It would seem, from fur- 

 ther investigations, that surface tension not only 

 determines the condensations in the films and else- 

 where in the organisms, but also maintains these 

 condensations against the forces of diffusion. — Sir 

 David Bruce, Majors D. Harvey and A. E. Hamerton, 

 and Lady Bruce : Morphology of various strains of 

 the trypanosome causing disease in man in Xvasaland. 

 IV., The Mzimba strain. — Helen L. M. Pixell : Notes 

 on Toxoplasma gondii. — J. C. F. Fryer : An investiga- 

 tion by pedigree breeding into the polymorphism of 

 Papilio polytes, Linn.— Dr. S. Russ and Dr. Helen 

 Chambers : The action of radium rays upon the cells 

 of Jensen's rat sarcoma. 



Physical Society, May 16.— Prof. C. H. Lees, vice- 

 president, in the chair. — Dr. W. Makower and Dr. S. 

 Russ : Some experiments to detect /3 rays from radium 

 A. When an atom of radium A disintegrates an a 

 particle is expelled which carries with it two positive 

 atomic charges. At the same time the radium B atom 

 formed recoils with a single positive charge. To 

 explain this it is necessary to suppose that three nega- 

 tive electrons are expelled during the process. If 

 these are emitted with a high velocitv thev should 

 appear as 3 rays capable of detection; or thev might 

 consist of a slowly moving 6 radiation which would 

 escape such detection. The experiments, made by 

 both methods in the hope of detecting £ rays from 

 radium A, failed to reveal any such radiation.— Dr. J. 

 Robinson : Dust figures. The ripple formation in 

 Kundt's tube was explained by W. Konig in 1891. 

 His theory was based on the hydrodynamical forces 

 between two particles in a stream. Certain measure- 

 ments on dust figures produced by an electric spark 

 have shown that these figures also can be explained 

 in a similar way to the Kundt's tube figures. Cook 

 suggested that viscosity must be introduced in order 

 to account for the formation, of ripples. The author 

 shows that it is possible to account for ripple forma- 

 tion without introducing viscous forces at all. In the 

 case of the Kundt's tube figures there is a variation 

 of velocity of the air from a node to an antinode, 

 which produces a variation in the forces, and this 

 causes the powder to lose its uniformity of distribu- 

 tion and to form ripples. The necessary constraints 

 for the ripples are forthcoming without the introduc- 

 tion of viscosity.-— Dr. Haworth : Vibration galvano- 

 meter design. (1) The maximum amount of power 

 available for vibrating the moving svstem of a vibra- 

 tion galvanometer of the moving-coil tvpe is V s '4R. 

 As the frequency of the instrument is raised the losses 

 increase rapidly, so it is an advantage to be able to 

 increase the useful power input per unit voltage ; the 

 resistance of the instrument must be decreased. This 

 can be done in a galvanometer of the Duddell tvpe by 

 leading the current in and out at the bottom bridg 

 and short-circuiting the wires at the top bridge, an" 

 it results in an increase of sensibility. (2) Owing- to 

 the losses in the moving system increasing at a 

 greater rate than the first power of the frequency, and 

 because the frequency of the svstem increases at a 

 slower rate than the reciprocal length of the string 

 on account of the mass of the mirror, the flux density 

 must be increased as the frequency increases. As the 

 losses are low at low frequency and the mass of the 

 mirror is not large, then, compared with the mass of 

 the wire, the flux density required is moderate; but 

 at his'h frequencies the flux density required is large. 

 To obtain this result economically it is convenient to 

 make the depth of the poles small compared with the 

 maximum length of the wires. (3) A combination of 

 ft) and (2) makes a satisfactory instrument with a 

 much flatter voltmeter-sensibilitv-frequencv curve thin 

 obtained usually. 



NO. 2275, VOL. 91] 



Dublin. 

 Royal Dublin Society, May 20.— Prof. James Wilson 

 in the chair. — W. J. Hartley : A violet colouring 

 matter and its production by a certain bacterium. 

 The bacterium was isolated from the water supply of 

 a creamery. The cultural characters resemble those 

 of both Bacterium violaceus and B. ianthinus, as 

 described by Mace. The colour was best produced 

 on potato. Colour was not produced at 37 C, in the 

 absence of air, or in the absence of more moisture 

 than was sufficient for the growth of the organism. 

 In artificial media colour was produced in the absence 

 of peptone. The colouring matter extracted with 

 alcohol is an amorphous blue-black, solid, without 

 surface reflection. A weighed quantity was dissolved 

 in alcohol, and the absorption spectra were examined 

 optically and photographically at various dilutions. 

 The spectra extended from A.670 in the red to A227 in 

 the ultra-violet. At the greatest dilution only one 

 absorption band was observed, starting at ^6439, and 

 extending towards, but not further than, X5000 ; the 

 ultra-violet absorption is general, with no indicati in 

 of bands. This spectrum differs from that of the 

 dyes, such as Hoffmann's violet, and from the spectra 

 of violet colouring matters extracted from natural 

 sources by Schneider, Moseley, Molisch, Krukenburg, 

 and Lecoq de Boisbaudran. The chemical reactions 

 of the solution resemble those of some natural violet 

 colouring matters. It is an oxygenated substance 

 which, in the presence of light, oxidises substances 

 such as alcohol. — Rev. Henry V. Gill : The effect of 

 a low potential electric current on photographic 

 plates. The object of this communication was to 

 describe some results which had been obtained from 

 experiments on photographic plates. There is a great 

 deal of uncertainty concerning the nature of the 

 changes which take place in the sensitive surface of 

 such plates when they are exposed to the action of 

 light and other influences. Many physicists have 

 studied the effect of passing electric sparks over the 

 surface of dry photographic plates. On development 

 a record of the path traversed by the discharge is 

 obtained. The blackening of the plate is in great 

 part due to the luminosity accompanying the dis- 

 charge, and it is consequently difficult to determine 

 the part played by the current as distinct from the 

 luminosity of the spark. The discharge was non- 

 luminous, and of comparatively low voltage, from 

 200 to 400 volts. The results obtained show that the 

 effect of such a current on sensitive plates is com- 

 plicated, and depends to a great extent on the nature 

 of the terminals placed at the surface of the plate, 

 between which the discharge takes place. The ions 

 coming from the positive terminal seem to play the 

 chief part in the reaction. When, for example, copper 

 is employed as positive terminal, a considerable region 

 of the plate surrounding" the point of contact is found 

 on development to be blackened ; on the other hand, 

 when platinum is used no blackening of the plate 

 is produced. Silver and other metals produce char- 

 acteristic effects. The effect at the negative terminal 

 is very much less and does not depend on the nature 

 of the terminal. 



Paris. 

 Academy of Sciences, May 26.— M. F. Guyon in the 

 chair. — Emile Picard ; Concerning- the recent meeting 

 of the International Association of Academies. A 

 short account of the subjects discussed at the meeting 

 at St. Petersburg.— Paul Appell ; The Hermite poly- 

 nomials U,„,„ and (heir analogues connected with 

 spherical functions in hyperspace. — P. Chofardet ; 

 Observations of the Schaumasse comet, 1913a, made 

 at the Observatory of Besancon with the bent equa- 

 torial. Positions are given for May 21 and 24. On 



