142 



NATURE 



[June 9, 1898 



which are exposed on the southern slopes of the St. Gothard 

 Pass and for some distance west and east, on the northern side 

 of the Val Bedretto. These rocks in the field might be regarded 

 as highly-altered sedimentary strata (as the author once thought) 

 or as a group of igneous rocks (originating possibly in magmatic 

 differentiation) affected by fluxion-movements anterior to con- 

 solidation. To the latter view he now inclined, but considered 

 the schistosity and the peculiar minor structures to be the results 

 of crushing (generally without marked shearing) followed by 

 very considerable mineral reconstruction. — On the metamorphism 

 of a series of grits and shales in Northern Anglesey, by Dr. C. 

 Callaway. While mechanical force has been concerned in pro- 

 ducing the more intense metamorphism of the lower part of the 

 series, the author was not disposed to advance this as the sole 

 cause of the changes produced. — On a volcanic series in the 

 Malvern Hills, near the Herefordshire Beacon, by H. D. 

 Acland. It is suggested that the rocks may be the volcanic 

 equivalents of the plutonic rocks of the Malvern axis, faulted 

 down and protected by the bend in the axis which occurs in the 

 neighbourhood of the Herefordshire Beacon, 



Chemical Society, May 19.— Prof. Dewar, President, in the 

 chair. — The following papers were read: — The liquefaction of 

 hydrogen and helium, by J. Dewar. Hydrogen was liquefied by 

 allowing the gas cooled to -205°, and under 180 atmos. 

 pressure, to expand ; about i per cent, of the gas liquefied. 

 Helium was liquefied by cooling in liquid hydrogen. — The 

 action of formaldehyde on amines of the naphthalene series. 

 Part I, by G. T. Morgan. Formaldehyde acts on )3-naphthyl- 

 amine in alcoholic solution containing hydrochloric acid yield- 

 ing naphthacridine, and bases of the composition CjiHijN, 

 Cs-jHigNo, and C.^gHigNo. — On the constitution of oleic acid and 

 its derivatives, Part i, byF. G. Edmed. Pelargonic and azelaic 

 acids, as well as two hydroxystearic acids, are formed on oxidis- 

 ing oleic and elaidic acids ; the author therefore assigns the 

 constitution CH3(CH2)7CH : CH(CH2)7 CO^H to the two latter 

 acids. — Stereoisomeric derivatives of camphor, by T. M. Lowry. 

 On recrystallising dibromochlorocamphor, 



/CCl Br. 

 C^HiaBr/ >, 



\co / 



its rotatory power changes, indicating the existence of stereo- 

 isomerism. 



Cambridge. 

 Philosophical Society, May 16.— Mr. F. Darwin, Presi- 

 dent, in the chair. — On the figures produced on photographic 

 plates by electric discharges, by Mr. J. A. McClelland. When 

 an electric discharge has passed to the surface of a photographic 

 plate a distinct figure is produced when the plate is developed, 

 and the form of the figure is dependent on the sign of the dis- 

 charge. The object of the paper is to determine whether these 

 figures are produced by some direct electrical action on the film, 

 or by the light which accompanies the discharge. Figures were 

 taken with the plates in air at various pressures, and as the 

 pressure was diminished the branching lines in the figures be- 

 came broader and less distinct, as they would if produced by the 

 light of the discharge in the air close to the film. The trans- 

 parency of various substances was tested, and while, no effect 

 was produced through thin slips of ebonite, the effect through 

 glass and mica was quite distinct. The experiments seemed to 

 show that the light of the discharge was chiefly instrumental in 

 producing the figures. The difference in the positive and nega- 

 tive figures is due to the difference in the discharge in air in the 

 two cases. — On a method of facilitating the measurement of 

 temperature by platinum thermometry, by Mr. E. B. H. Wade. 

 Attention is drawn to the inconvenience arising from the fact 

 that equal increments of the resistance of platinum wire do not 

 represent equal increments of the temperature. A form of 

 Wheatstone's Bridge is then described in which the incon- 

 venience disappears. The resistance of the platinum is balanced 

 by that of two resistance boxes in parallel, plugs being trans- 

 ferred from one box to the corresponding places in the other till the 

 balance is obtained. It is shown that when this is done, equal 

 increments of the resistance in one box may be made to repre- 

 sent equal increments in the temperature of the platinum wire. 

 Accuracy is not sacrificed in obtaining the simplification result- 

 ing from this method. — The development of Feripatus novce- 

 britannicE, by Dr. A. Willey. The ova are without yolk, and 

 the nutrition of the embryo is effected by the development of a 

 large trophic vesicle, which occupies the entire dorsum of the 



embryo, and projects far in front of the embryo as a head-fold 

 and behind as a tail-fold. The trophic vesicle is thus a hollow 

 closed cylinder lined internally by endoderm and externally by 

 ectoderm, the cells of the latter being adapted for absorption of 

 nutriment. The trophic folds were compared with the amniotic 

 folds of insects. The trophic cavity becomes the gastral cavity 

 of the adult, and in the transformation from one to the other 

 the endoderm undergoes certain changes. It secretes a basal 

 membrane and a cuticular membrane simultaneously with a great 

 increase in thickness ; and between the two membranes the 

 endoderm contains numerous small and large yolk-like globules, 

 which are probably to be regarded as reserve nutrient matter to 

 tide the embryo over the first few days of its independent life. 

 This late deposition of reserve nutrient matter derived ultimately 

 from the maternal organism, as opposed to foreign ingested 

 matter, is probably of some significance with regard to the 

 question of the lecithality of the ovum. The embryo lies outside 

 on the ventral surface of the trophic vesicle just as an insect 

 embryo lies upon the yolk.— On Rontgen rays and ordinary 

 light, by Mr. C. Godfrey. Prof. J. J. Thomson has shown that 

 the sudden stoppage of an electron gives rise to a thin electric 

 pulse which is propagated through the medium ; these pulses he 

 identifies with Rontgen rays. The application of Fourier 

 analysis shows that the assemblage of these pulses is equivalent 

 to a mixture of simple harmonic waves of all wave-lengths ; a 

 peculiar feature is that these waves are absent whose lengths are 

 sub-multiples of the thickness of the pulse. Most of the energy 

 is resident in the short waves ; but about i/iooo of the whole 

 energy will be visible light. The pulses suggested by Sir George 

 Stokes as affording an explanation of Rontgen rays differ from 

 Prof. Thomson's in one respect ; the integrated displacement 

 through the thickness of the pulse is zero. On this property 

 Sir G. Stokes bases his proof that there will be no diffraction ; 

 and it may be seen that these pulses (taken to be of the same 

 thickness as Prof. Thomson's) will have only lO"^ of this 

 energy in the visible spectrum. — On the possibility of deducing 

 magneto-optic phenomena from a direct modification of an 

 electro-dynamic energy function, by Mr. J. G. Leathem. The 

 method initiated by Maxwell for the explanation of the Faraday 

 effect depended on the direct insertion of a magneto-optic term 

 in the energy. . This method was extended by Fitzgerald and 

 others to the explanation of Kerr's effect, namely the modifica- 

 tion introduced in the circumstances of optical reflexion by 

 magnetisation of the reflector. A difficulty occurred, however, 

 in satisfying all the interfacial conditions, which virtually showed 

 that such a scheme was not formally self-consistent. The origin 

 of the discrepancy has been traced by Mr. Larmor (" Report on 

 the Action of Magnetism on Light," Brit. Assoc, 1893) ^ 

 omission to secure what may for shortness be called the electro- 

 motive incompressibility of the medium : in the ordinary 

 problem of optical reflexion there is no tendency for this to be 

 disturbed, but when Maxwell's magneto-optic energy terms are 

 included, the reaction against compression introduces what 

 may be termed an electric pressure, which must appear in the 

 equations. It was necessary to compare the modified scheme 

 thus obtained with experimental knowledge : and the calculations 

 given in this paper show that in fact it does not represent the 

 phenomena. The paper is only a summary of the actual calcu- 

 lations, because since they were completed the author has shown 

 ("On the Magneto-optic Phenomena of Iron, Nickel and 

 Cobalt," Phil. Trans. 1897), that the other rigorous theory form- 

 ulated as an alternative by Mr. Larmor {loc. cit.), which leads 

 to an analytical scheme practically the same as those advanced 

 on various hypotheses by Fitzgerald, Goldhammer, Basset, 

 Drude, and others, is in much more satisfactory agreement with 

 experiment. This brief history of the subject shows the de- 

 sirability of the examination of the consequences involved in the 

 former method of explanation ; the result is, however, what was 

 to be expected by those who adhere to the more recent form- 

 ulation (Larmor : " A Dynamical Theory of the Electric and 

 Luminiferous Medium," Part 3, Phil. Trans., 1S9S) of optical 

 theory, which treats a material medium as free 3ether pervaded 

 by discrete molecules involving in their constitution electrons 

 considered as nuclei of intrinsic ^ethereal strain. On such a view 

 a continuous energy function is not the starting-point, and the 

 influence of these discrete nuclei could hardly be conceived to 

 modify the propagation in the intervening aether in so fund- 

 amental a manner as an electromotive pressure would demand. 

 — On the solutions of the equation (v'-H/c-) <f/ = o in elliptic co- 

 ordinates and their physical applications, by Mr. R. C. 



NO. 1493, VOL. 58] 



