April 21, 1898] 



NATURE 



599 



and is mainly concerned with a recent paper by F. S. Macaulay, 

 viz. point groups in relation to curves {London Math. Soc. Proc, 

 vol. xxvi. pp. 495-544). — Prof. Beman points out the use of?, 

 by Euler, to represent an imaginary, thus disposing of Gau.ss's 

 claim to priority. — The remaining matter consists of shorter 

 notices {i.e. reviews), notes, and publications. 



SOCIETIES AND ACADEMIES. 

 London. 



Royal Society, March lo. — "An Extension of Maxwell's 

 Electro-magnetic Theory of Light to include Dispersion, 

 Metallic Reflection, and Allied Phenomena." By Edwin 

 Edser, A.R.C.S. Communicated by Captain W. de W. Abney, 

 C.B , F.R.S. 



All media are considered, as far as their properties afifect the 

 propagation of electro-magnetic waves of frequencies as great 

 as those of light, to consist of molecules, each comprising, in 

 the simplest case, two oppositely charged atoms at a definite 

 distance apart. In an electric field the positive atoms move to 

 points of lower, and the negative atoms to points of higher 

 potential. In doing so a molecule may be subjected to a 

 rotational displacement, or its constituent atoms may be separated 

 more widely from each other. Equations are determined giving 

 the relation of the specific inductive capacity (the electric strain 

 being steady) to the molecular displacements. 



Maxwell's well-known equations are modified by adding to 

 the total displacement current a term representing the convection 

 current per unit volume. The existence of free ions is not 

 considered capable of materially affecting the value of the 

 refractive index for light waves. Subsidiary equations represent- 

 ing the conditions of the atomic vibrations are assumed, and the 

 refractive index, ju, is finally given by the equation 



\>.\ represents the specific inductive capacity as previously deter- 

 mined. 



Double refraction in a uniaxal crystal is explained by suppos- 

 ing the axes of the molecules to be arranged with their axes all 

 parallel to one direction. Electric disturbances perpendicular 

 to this direction will produce a molecular rotation, whilst those 

 parallel to the molecular axes will produce a separation of the 

 constituent atoms. Hence two different propagational velocities 

 will follow. The connections of the above theory with Kerr's 

 well-known experiments on the double refraction experienced 

 by light when traversing a liquid dielectric subjected to electric 

 stress, and the facts of pyro-electricity are obvious. 



In order to account for the phenomena of the propagation of 

 light in metals, a viscous term is added to the equation for the 

 molecular vibrations. The square of the refractive index is hence 

 derived as a complex quantity, the imaginary part being essen- 

 tially positive. In those cases where the real part of the re- 

 fractive index is a large negative number, it is pointed out that 

 the velocity of propagation of light waves will be inversely 

 proportional to the molecular viscosity (and therefore to the 

 electrical resistance) of the metal, agreeing with Kundt's ex- 

 perimental relation. 



Geological Society, April 6.— W. Whitaker, F.R.S., 

 President, in the Chair. — Prof. T. Rupert Jones exhibited 

 and commented upon a series of large stone implements, sent to 

 England by Mr. Sidney Ryan, from the tin-bearing gravels of 

 the Embabaan in Swaziland (South Africa). Some implements 

 lent by Mr. Nicol Brown, and analogous implements of rough 

 quartzite, from Somaliland, lent by the Rev. R. A. BuUen, 

 were also exhibited. — Prof. H. G. Seeley exhibited the humerus 

 of a Plesiosaurian in which the substance of the bone was almost 

 entirely replaced by opal. He explained that the fossil was 

 from the opal mines of New South Wales. — On some Palreolithic 

 implements from the plateau-gravels, and their evidence con- 

 cerning " Eolithic " man, by W. Cunnington. Although at 

 first inclined to believe that the chipping on the " Eoliths " of 

 the plateau -gravels was the work of man, the author has been 

 led to recant this opinion by the detailed study of specimens 

 lent or given to hint by Mr. B. Harrison. His reasons are 

 mainjy based on the facts that the chipping is of diffierent dates, 

 even.upon the same specimen, and that it was produced after the 

 specimens were embedded in the gravel. A further series of 

 specimens, which, although not found actually in situ in the 

 gravels, present undoubted evidence that they came from these, 



NO. i486, VOL. 57] 



are considered by the author to be of Palaeolithic type. One of 

 them appeared to have gone through the following stages : first 

 it was fashioned by man into a Palaeolithic implement, then it 

 was abraded, broken and chipped along one edge in the same 

 fashion as the alleged " Eolithic " working ; finally it was 

 stained, marked with glacial strioe, and covered with a thin layer 

 of white silica. This implement appears to prove that 

 Palaeolithic man lived on the Kentish plateau before or during the 

 deposit of the plateau-gravels, and that the " Eolithic" chipping 

 is not the work of man. A long discussion followed the reading 

 of the paper, and was summed up by Dr. Gregory, who replied 

 on behalf of the author. Dr. Gregory said he noticed in the 

 discussion absolute unanimity on one point : no one denied 

 that some of the specimens exhibited were worked by man, and 

 that they were genuine plateau-gravel flints, which must have 

 been flaked before the deposition of the gravels. Every speaker 

 had therefore admitted that man lived in Kent before or during 

 the deposition of part of the plateau-gravels. Thanks, there- 

 fore, to Mr. B. Harrison's magnificent perseverance and in- 

 dustry, man's age in Kent had been carried back one stage 

 further. In the congratulations to Mr. Harrison on that achieve- 

 ment, no one would join more heartily than the author. But 

 that admission did not affect the question of the specimens 

 described as "Eoliths" or "rudes." Those who believed in 

 these specimens still could not agree as to which are genuine and 

 which are not. He thought the critical points of the paper had 

 been ignored in the discussion : no attempt had been made to 

 show that the implements were not Palseolithic, or that the 

 " Eolithic " work was not later than the Palaeolithic work. He 

 quoted the opinions of Mr. Montgomery Bell and Mr. Harrison 

 to show the identity of the working of the broken edge of the 

 Palreolith with that of the Eoliths. It was only the " Eolithic " 

 implements that the author had denied. The wide general 

 importance of this question was the claim that the Kent 

 plateau had been the, home of a primitive pre-Palseolithic 

 people, which, he held, the author's arguments conclusively 

 disproved. — On the grouping of some divisions of Jurassic 

 time, by S. S. Buckman. The author argues for an arrange- 

 ment in the division of Jurassic time based upon the zoological 

 phenomena of the Ammonite fauna. 

 Paris 

 Academy of Sciences, April 12. — M. van Tieghem in 

 the chair. — The President announced to the Academy the recent 

 death of M. Aime Girard, Member of the Section of Rural 

 Economy (see p. 587). — Observations relative to the action of 

 oxygen upon sulphide of carbon and to the chemical influence of 

 light. Preliminary action determining the chemical changes, by 

 M. Berthelot. In a mixture of air with the vapour of carbon 

 disulphide exposed to diffused light no change was found to have 

 occurred at the end of a year. Under the influence of direct 

 sunlight, however, oxidation soon commences, but is by no 

 means completed in a year. The effect produced is, therefore, 

 not simply proportional to the luminous intensity, unlike the 

 combination of hydrogen and chlorine, which commences in 

 the most feeble diff'ussd light and increases with the intensity. 

 — On the absorption of oxygen by pyrogallate of potassium, 

 by M. Berthelot. The principal defect of the common nriethod 

 of estimating oxygen consists in the simultaneous formation of 

 small quantities of carbonic oxide. A number of experiments 

 are described in which the influence of temperature, dilution, 

 and the relative proportions of pyrogallol and potash upon the 

 course of the reaction is ascertained. The author concludes 

 that, in order that only negligible quantities of carbonic oxide 

 maybe produced,' the absorption should be effected in presence 

 of a large excess of potash and an amount of pyrogallol capable 

 of absorbing four or five times the volume of oxygen likely to 

 be present. From the products of the reaction an oxyquinone 

 (C6H4O5) may be extracted with ether, after acidification. This 

 compound will be described later.— Flesh and starch compared 

 with sugar, as regards nutritive value, in the case of a working 

 subject, by M. Chauveau. — Addition to a preceding com- 

 munication concerning the theory of quadratic forms,: by M^^ 

 de Jonquieres.-rQbsei;v»tiop3 of Copiet Perrine, made at the', 

 observatory of Algiers, by MM. Rambaud ind F. Sy*— Ex*i 

 pression of the derivatives of theta functions of two arguments • ' 

 by means of the squares of theta functions, by M. E. Jahnke. — 

 On the systems of differential equations satisfied by quadruply 

 periodic functions of the second species, by M. M. Krause. — 

 On the equations of the theory of elasticity, by MM. Eugene 

 and Francois Cosserat.-^On the passage of electric waves from 



