April 24, 1902 J 



NATURE 



603 



which had recently been announced as vaiiable. Examination 

 of the photographs taken at Oxford appeared to show that the 

 variabiliiy of these stars had been assumed on insufficient 

 grounds. — Lantern sHdes of a Leonid meteor, taken by Prof. 

 Rees and Mr. Post, were .shown on the screen. — The secretary 

 partly read a paper by Mr. Whitmell, calling attention to the cir- 

 cumstances on July 17, 1902, when there will occur a transit of the 

 earth over the sun, which will be partially visible to an observer 

 on Saturn through the Ca.ssini division of the ring. At the same 

 time a terrestrial observer, suitably placed, will be able to view, 

 through that division, a portion of the planet's disc lit up by 

 sunlight, so that a part of the division will appear bright instead 

 of dark. — -The secretary also partly read a paper by Prof. Barnard 

 on the proper motion of stats in the dumb-bell nebula. The 

 author concluded that the supposed proper motion was not real, 

 but due to inaccuracies in earlier measures of position. 



Mathematical Society, April lo. — Dr. E. \V. Hobson, 

 F.R.S., president, and, temporarily. Dr. J. Larnior, F.R.S., 

 in the chair. — Dr. Hobson communicated a note on divergent 

 series. After explaining the method by which Borel attaches a 

 definite arithmetical meaning to certain classes of divergent 

 series, by the use of related convergent series, he gave an 

 account of an extension to a wider class of series which are such 

 that the radius of convergence of Borel's related series is zero. 

 This extension involves the use of Bessel's functions of imaginary 

 argument in place of Gamma functions. — -Prof. Love gave a 

 preliminary account of some researches concerning stress and 

 strain in two-dimensional elastic systems. Solutions of two- 

 dimensional problems, besides being useful for purposes of 

 illustration, often lead to important results in regard to the 

 strength of long prisms or of thin plates. The strain and dis- 

 placement can be obtained by the superposition of effects due 

 to singularities of functions of a complex variable ; and there 

 are relations between problems connected with prisms of 

 different .sections, the areas within the two .sections being trans- 

 formed, one into the other, by a conformal representation. — 

 The following papers were communicated from the chair : — Dr. 

 Baker, Further applications of matrix notation to integration 

 problems. The finite equations of the adjoint group of any 

 continuous group, whether the parameters are canonical or not, 

 are expressed in terms of certain matrices, and it is shown that 

 any transformation of the adjoint group can be resolved into a 

 succession of two transformations respectively of the first and 

 second parameter groups. \ formula is obtained for the general 

 integral of any set of simultaneous linear differential equations 

 with variable coefficients, in a form valid for the whole of the 

 Mittag-Lcfllcr star region over which the integrals exist. The 

 method of obtaining this formula can be applied to establish the 

 existence of, and to calculate, the integrals of a system of 

 differential equations with real independent variables, the 

 coefficients in the equations being integrable functions, but not 

 necessarily continuous functions. — Dr. L. E. Dickson, The 

 groups defined for an arbitrary field by the multiplication tables 

 of certain finite groups. The object of the paper is to discuss, 

 for all the cases that arise, the groups defined by certain simple 

 types of finite groups. The methods employed are quite 

 elementary and are practically independent of the general 

 theory, as worked out by Frobenius and Burnside. Illustra- 

 tions are given of a general method of determining the irre- 

 ducible factors of the group-determinant. — Prof. T. J. I'A. 

 Bromwich, The convergence of series that represent a potential. 

 It is shown that the harmonic series by which the potential of a 

 body at an external point can be represented, in the neighbour- 

 hood of the point, converges generally at points within the 

 body. The nature of the domain of convergence is determined, 

 and illustrated by examples. 



Royal Meteorological Society, April i6. — Mr. W. H. 

 Dines, president, in the chair. — Captain D. Wilson-Barker 

 delivered a lecture on clouds. After some remarks on the 

 composition and the height of the atmosphere, the lecturer said 

 that until recent years comparatively little scientific attention 

 had been paid to the subject of clouds. This he largely 

 attributed to the lack of a simple practical classification. The 

 French naturalist Lamarck was probably the first to formulate 

 one, but Luke Howard, a London merchant, about 1S02 intro- 

 duced the first practical classification, which is still in use among 

 many observers. Clouds are formed by one of two cau.ses, viz. 

 (l) the mixing of two masses of moist air of unequal tempera- 

 tures ; or (2) through changes occurring in the atmosphere, 



NO. 1695, VOL. 65] 



where expansion and consequent loss of heat take place, causing 

 condensation of moisture. Captain Wilson-Barker said that a 

 simple primary classification is best arrived at by a two-fold 

 division of cloud types, viz. (i) "stratus," or sheet clouds, and 

 (2) " cumulus," or heap clouds. The former may be roughly 

 considered the cloud of a settled and the latter of an unsettled 

 state of the atmosphere. He showed by means of lantern slides 

 a number of cloud pictures illustrating certain varieties of both 

 main types. Under " stratus," or sheet cloud, the lecturer 

 included fog stratus, high stiatus, cirro-cumulus, cirrus, nimbus 

 and scud ; and under " cumulus," or heap clouds, he included 

 the ordinary cumulus, the shower cumulus, the squall cumulus 

 and roll cumulus. 



Paris. 

 Academy of Sciences, April 14. — M. Bouquet de la Grye 

 in the chair. — The president announced the death of M. Alfred 

 Cornu, member of the section of physics. — Researches on 

 electromotive forces, by M. Berthelot. A discussion of the 

 relations between the heats of dilution and the electromotive 

 force of concentration cells. From twenty-four to forty-eight 

 concentration cells of sodium chloride were placed in series, the 

 electromotive force of which, measured by the usual open cir- 

 cuit methods, was 5-7 volts ; it was not, however, found possible 

 to decompose water by such a battery. — On the fundamental 

 theorem of the theory of Abelian functions, by M. Paul Pain- 

 leve. An elementary and direct demonstration is here given, 

 depending on the ordinary theory of functions of one variable. 

 — The resistance due to companion waves, by M. de Bussy. It 

 is shown by reasoning based partly on the author's own experi- 

 ments and partly on those of Froude, that in a ship the form of 

 which corresponds to the maximum speed the resistance due to 

 the companion waves varies as the sixth power of the speed. — 

 Principle of a new interference refractometer, by M. G. Sagnac. 

 An arrangement of Fresnel's mirrors is described giving circular 

 fringes without the use of a slit. It would appear to be pre- 

 ferable to the arrangement of Michelson in the case where it is 

 necessary to have a temjierature rigorously the same in the 

 corresponding regions of the two interfering bundles. — Some 

 remarks on the theory of Duddell's singing arc, by M. Paul 

 Janet. The singing arc discovered by Duddell furnishes a 

 means of obtaining an alternating current by means of a con- 

 tinuous electromotive force. The distribution of the energy 

 and the values of the current in the different parts of the circuit 

 are worked out and a summary of the results given. — Variations 

 in spark spectra, by M. B. Eginitis. On sparking between poles 

 of two metals, a gradual increase in the self-induction of the 

 spark circuit frequently resulted in the elimination of the 

 spectrum of one of the metals. It was not found possible to 

 eliminate the spectrum of mercury, sodium and potassium in 

 this way. — Retrograde diffusion of electrolytes, by M. J. Tho- 

 vert. Measurements are given of the diffusion of a solution of 

 an electrolyte containing an acid with the same negative ion 

 into a solution of the electrolyte alone. The results were in 

 complete accord with the electrolytic diffusion theory of Nernst. 

 — Contribution to the theory of the dynamo, by M. N. "Vasi- 

 lesco-Karpen. — Remarks on the working of coherers and auto- 

 decoherers, by M. O. Rochefort. It has been found by 

 experiment that all coherers with spontaneous decohesion may 

 be reduced to the state of ordinary coherers by diminishing the 

 pressure of the imperfect contacts ; sufficient experimental data 

 have not yet been accumulated as regards the reciprocal of this. 

 It has, however, been found that in certain cases with metal- 

 metal or powder contacts the radio-conductor can be brought to 

 the state of auto-decoherers by simple increase of pressure. — 

 Luminous sensation as a function of the time, by MM. Andre 

 Broca and D. Sulzer. — Values of the electrical resistance, the 

 index of refraction and of the rotatory power of normal blood 

 serums, by MM. Dongier and Lesage. With a view of 

 utilising various physical methods for the study of certain patho- 

 logical cases, data were accumulated for more than 200 samples 

 of blood serum, care being taken to collect from only healthy 

 subjects. — On the composition of gaseous hydrates, by M. de 

 Forcrand. After remarking on the experimental difficulties in 

 the determination of the exact composition of the hydrates of 

 such a gas as sulphur dioxide, the author develops a new method 

 ba.sed on the fixed ratio between the heat of formation of 

 the solid hydrate and the absolute temperature at which 

 this hydrate has a pressure of 760 mm. — The action of 

 hydrogen upon strontium amalgam, by M. Guntz. The 

 dissociation pressures of strontium hydride are measured at 



