June 9, 1887] 



NA TURE 



143 



supposed to be supplied with constant mean current or constant 

 mean potential difference, this is not to be altered by the current 

 in the secondary. (3) No magnetic leakage ; so that the co- 

 efficient of mutual induction is the geometric mean between their 

 coefficients of self-induction, (4) The quantities of copper in the 

 primary and secondary are to be equal. These assumptions are 

 shown to be lei^itimate, and the ratios of the resistances, E.M.F.'s, 

 currents, and coefficients of self-induction are expressed in tenns 

 of the ratio of the numbers of convolutions, which ratio is 



s 



represented by/ = " \ 

 shown that E., = 



From analogy with the dynamo it is 



^M 



=Ej, where « = 2-nn, E^ and E^ 



the E. M. F. 's of the primary and secondary respectively, and 

 Rj and Lj the resistance and self-induction of the primary coil. 



ttfM Ej 



If R, be negligible, the above reduces to Ej = "7=v=; = — > 



since |J = p"', and M = VLiLj. The latter part of the paper 



contains a general investigation of two neighbouring cir- 

 cuits both having self-induction, and it is shown that the 

 effective resistance of the primary is increased, and the self- 

 induction decreased by closing the secondary circuit. Mr. 

 Kapp said the investigations assumed the coefficients of in- 

 duction to be constants, and that the phases of current in 

 primary and secondary were opposite. The former being by no 

 means true, he asked. What values were to be taken ? and he 

 believes the phases of current are not opposite in ordinary 

 transformers. Mr. Swinburne protested against the use of 

 formulje to calculate the inductions when the required data could 

 be obtained much more accurately from Dr. Hopkinson's curves 

 on magnetization of iron. lie also thought the curve of sines 

 did not nearly represent the current curve for ordinary machines. 

 Mr. Bosanquet thought the effective magnetization of a trans- 

 former would be different from that of a dynamo, for, in the former, 

 permanent magnetism was not utilized. In reply to Mr. Kapp 

 and Mr. Swinburne the author pointed out that as the coefficients 

 of induction enter in both numerator and denominator, it would 

 not matter which set of values v^ere taken if the resistance was 

 small compared with wL ; and that self- induction tends to 

 smooth out irregularities in the current curve. Prof. Ayrton 

 described a method of regulating a series transformer devised by 

 himself and colleague some two years ago, based on analogy 

 with a compound dynamo. Referring to the variation of L with 

 current, he sketched a curve connecting them, obtained by Mr. 

 Sumpner at the Central Institution, and mentioned that the 

 E.M.F. curve of a Ferrani dynamo is an exact sine curve. He 

 believes problems involving alternating currents would be greatly 

 simplified by using a new stt of measurable quantities, such as 

 will render the equations as simple as possible. At Prof. 

 Thomps n's request. Prof. Ayrton exhibited a lecture experiment 

 illustrating the action of transformers. The secondaries of two 

 ordinary induction coils were joined in series through long fine 

 wires, and an incandescent lamp placed in the primary circuit of 

 one, lighted up on completing the primary of the other coil in 

 which a battery was placed. — On magnetic torsion of iron wires, 

 by Shelford Bidwell. This is an account of experiments made 

 on the twisting produced by sending a current along magnetized 

 iron wires, and the author shows that Wiedemann's explanation 

 of these phenomena (by assuming a difference in molecular 

 friction at the polar and lateral surfaces of magnetized molecules), 

 is unsatisfactoi-y. The wires were magnetized longitudinally by 

 means of a solenoid in the axis of which the wires were sus- 

 pended. To obtain consistent results it was found necessary to 

 demagnetize the wire between the observations. This is done 

 by reversed currents of gradually decreasing strength, and a 

 simple arrangement of rheostat and commutator devised for this 

 purpose was exhibited. Two sets of experiments were made, in one 

 of which the current in wire or solenoid was kept constant whilst 

 that in the o*her was varied. The amount of twisting does not 

 increase continuously when the currents are increased, but attains 

 a maximum when the inclination of the helix, representing the 

 direction of magnetization, is inclined at about 33° to the axis of 

 the wire. When the current in the solenoid was kept constant 

 and that in the wire increased, permanent deflections remained 

 on stopping the current. For small currents in the wire this 

 deflection was diminished on starting the current, whilst stronger 

 currents increased the deflection. For some intermediate value 



of the current, no change took place, and this value was- 

 dependent on the current in the solenoid. Experiments were 

 shown illustrating these phenomena. 



Amhropological Institute, May 24. — Mr. Francis Galton, 

 F.R.S., President, in the chair. — Dr. George Harley, F.R.S., 

 read a paper on the relative recuperative powers of man living 

 in a rude, and man living in a highly civilized state ; in which 

 he brought forward a number of hitherto unpublished, though 

 mostly well-known facts, demonstrating that the refining in- 

 fluence of civilization had not been altogether the unalloyed 

 boon we so fondly imagine it to have been. For the cases cited 

 went far to demons' rate the fact that while man's physique, as 

 well a; his mental power, had increased during his evolution 

 from a barbaric slate into a condition of dietisJauce, his recupera- 

 tive capacity, on the other hand, has materially deteriorated. In 

 fact, it appeared from the examples cited that every appliance 

 adding to man's bodily comfort, as well as evei-y contrivance either 

 stimulating or developing his mental faculties, while increasing 

 his persona! enjoyments materially diininishes his animal vitality ; 

 rendering him less able to resist the effects of lethal bodily 

 injuries, or recover from them as well and as quickly as his 

 barbaric ancestors, or his less favoured brethren. — Mr. G. L. 

 Gomme read a paper on the evidence for Mr. McLennan's theory 

 of the primitive human horde : and a communication by Mr. 

 Samuel Gason on the Dieyerie Tribe of South Australia was 

 also received. 



Mineralogical Society, May 10. — Mr. L. Fletcher, Presi- 

 dent, in the chair. — It was reported that Mr. F. Pearce, of 

 Maritzburg, Natal, and P. of. Albert Chester, of Clinton, N.Y., 

 had been elected members in April. — The following papers were 

 read : — Microscopical studies on some eruptive rocks from the 

 Caucasus and Armenia, by Dr. Hjalmar Gylling, of Ilelsingfors. 

 — Note on some specimens of glaucophane rock from the He de 

 Groix, by Rev. Prof. Bonney, F.R. S. — On the crystalline form 

 of kreatine, by Mr. L. Fletcher. — Note on francolite, by Mr. F. 

 II. Butler. — On the meteoric iron seen to fall in the district ol 

 Nejed, in Central Arabia, in the spring of 1865, by Mr. L. 

 Fletcher. — On a granite containing andalusite from the Cheese- 

 wring, Cornwall, by Mr. J. J. H. Teall. — Prof. J. W. Judd, 

 F. R.S., exhibited some specimens and sections of tabasheer and 

 other forms of opal^ and made some observations thereon. 



Paris. 



Academy of Sciences, May 31. — M. Janssen in the chair. 

 — On the condition of stability in the movement of an oscillat- 

 ing system connected with a pendular synchronic arrangement, 

 by M. A. Cornu. A solution is here offered of a problem which 

 pre ents itself in the adjustment of certain apparatus of great 

 precision employed in physics and astronomy : how to render 

 the oscillations of a given mobile system, such as a pair of scales 

 or a galvanometer, exactly synchronous with a corresponding 

 periodical motion, such as that of a cIock's pendulum, and the 

 like. — On some crystallized metallic alloys of platina and tin, 

 by M. H. Debray. Resuming his former stU'Iies of these 

 alloys, the author here deals with those of platina and tin, with 

 formula, PtSn4 ; of rhodium, RhSn^ ; of iridium, IrSng ; and 

 of ruthenium, RuSn.,. Osmium yields no alloy with tin, in 

 which metal it crystallizes. — Progress of the Arago Laboratory, 

 by M. de Lacaze-Duthiers. An account is given of the im- 

 provements lately introduced at this marine zoological station, 

 which has been established at Banyuls. It is now fitted with a 

 7 horse-power steam-engine for supplying the aquarium with 

 water, and with submarine electric lamps for studying the habits 

 of the Mediterranean fauna. — On a fossilized tendril of A{;'/«///(^?« 

 Diimasii, Sap., by M. G. de vSaporta. Although traces of 

 rhizomes of Nympha'ace3e in various Tertiary formations are far 

 from rare, the present fjssil is specially remarkable for its 

 great beauty and excellent preservation. Apart from the 

 inner structure, which has been replaced by some amor- 

 phous substance, it retains all the exterior outlines of 

 the organ down to the minutest superficial details. — Re- 

 port on the velocities set up by the tides of the Pacific and 

 Atlantic Oceans in a canal establishing free communication 

 between these two basins, by M. Bouquet de la Grye. This is 

 the Report of the Commission appointed last year at the request 

 of M. de Lesseps to study the influence likely to be exercised on 

 the Panama Canal now in progress by the regular rise and fall 

 of the surrounding waters. It appears that the tidal currents, 

 much stronger on the Pacific than on the Atlantic side, can 



