522 



SCIENTIFIC NEVV^S. 



[June I, 1888. 



^t);Stract0 

 of papers:, ilertutejs, etc* 



ROYAL SOCIETY. 

 At the meeting on May 17th, Professor J. A. Ewing, 

 F.R.S., Professor of Engineering in University College, 

 Dundee, and Mr. G. C. Cowan, read a paper on the 

 " Magnetic Qualities of Nickel." 



The experiments described in the paper were made 

 with the view of extending to nickel the same lines of 

 inquiry as had been pursued by one of the authors in re- 

 gard to iron. (Phil. Trans. 1885, p. 523.) Cyclic pro- 

 cesses of magnetisation were studied in which a magne- 

 tising force of about 100 c. g. s. units was applied, re- 

 moved, reversed, again removed, and re-applied, for the 

 purpose of determining the form of the magnetisation 

 curve, the magnetic susceptibility, the ratio of residual 

 to induced magnetism, and the energy dissipated in con- 

 sequence of hysteresis in the relation of magnetic induc- 

 tion to magnetising force. Curves are given to show the 

 character of such cycles for nickel wire in three condi- 

 tions: the original hard drawn state, annealed, and 

 hardened by stretching after being annealed. The effects 

 of stress have also been examined (i) by loading and 

 unloading magnetised nickel wire, with weights which 

 produce cyclic variations of longitudinal pull, and (2) by 

 magnetising while the wire was subjected to a steady 

 pull of greater or less amount. The results confirm and 

 extend Sir William Thomson's observation that longitu- 

 dinal pull diminishes magnetism in nickel. The diminu- 

 tion is surprisingly great : it occurs with respect to the 

 induced magnetism under both large and small magnetic 

 forces, and also with respect to residual magnetism. The 

 effects of stress are much less complex than in iron, and 

 cyclic variations of stress are attended by much less 

 hysteresis. Curves are given to show the induced and 

 residual magnetism produced by various magnetic forces 

 when the metal was maintained in one or another of 

 certain assigned states of stress ; also by loading and un- 

 loading without alteration of the magnetic field. Values 

 of the initial magnetic susceptibility, for very feeble 

 magnetising forces, are stated, and are compared with the 

 values determined by Lord Rayleigh for iron, and the re- 

 lation of the initial susceptibility to the stress presefit is 

 investigated. The paper consists mainly of diagrams in 

 which the results are graphically exhibited by means of 

 curves. 



A paper " On jEolotropic Elastic Solids," by Mr. C. 

 Chree, M.A., Fellow of King's College, Cambridge, was 

 communicated by Professor J. J. Thomson.. This paper 

 is concerned with certain problems involved in the equi- 

 librium or vibration of various forms of elastic solid 

 structures. The case of a beam fixed at one end and 

 acted on by a system of forces at the other, was elaborately 

 treated by Saint-Venant. He, however, started with 

 certain assumptions, and one of the objects of Parts L 

 and n. of this paper is to treat this important problem 

 from a point of view independent of such assumptions. 

 The results obtained agree with Saint- Venant's. 



It is shown how, in most materials whose properties in 

 different directions are different, a circular bar when 

 twisted round its axis by forces at the ends must become 

 warped, and when exposed to pulling forces over its ends 

 must slightly alter the form of its cross section. The 

 variety in the character of these phenomena would allow 

 the nature of the material to be determined. 



In Part III. the effects of rotating a spheroidal body 

 about its axis of revolution are completely investigated, 

 and it is shown how the results may be extended so as 

 to apply to a thin circular disc rotating about a per- 

 pendicular to its plane through its centre, and to a long 

 thin cylinder rotating round its axis. The disc is shown 

 to increase in radius and to diminish in thickness, especi- 

 ally near the centre, so as to become bi-concave. The 

 long cylinder tends to shorten, while its ends remain flat. 



Part IV. deals with the longitudinal vibrations of a 

 circular bar of a material symmetrical round the axis. 

 It does not, as is usually done, assume the bar to be 

 indefinitely thin, but obtains an expression for the fre- 

 quency of the fundamental note and its harmonics, the 

 degree of whose accuracy is explicitly determined. It is 

 pointed out how the conclusions of the ordinary theory 

 diminish rapidly in accuracy as the ratio of the diameter 

 to the length of the bar is increased, and the higher the 

 order of the harmonic the more serious is the error. 



A paper on " The Electric Organ of the Skate," by 

 Professor J. C. Ewart, was also read, a notice of which 

 we give on page 508. 



LONDON MATHEMATICAL SOCIETY. 

 At the meeting held on Thursday, May loth, Sir J.. 

 Cockle (President) in the chair, 



Mr. E. B. Elliott read a fourth paper on " Cyclicants 

 or Ternary Reciprocants and Allied Functions." 



Mr. Cook Wilson gave a sketch of " Some Theorems on 

 Parallel Straight Lines together with some attempts to> 

 prove Euclid's Twelth Axiom." A long discussion en- 

 sued, in which Messrs. Henrici, Elliott, Buckheim and 

 the author took part. 



The following papers were taken as read : " On the 

 Flexure and the Vibration of a Curved Bar," by Mr. H.. 

 Lamb ; on the " Figures formed by the Intercepts of a 

 System of Straight Lines in a Plane, and Analogous- 

 Relations in Space of Three Dimensions," by Mr. T. 

 Roberts ; on " Lowe's Differential Equation," and on 

 "Stability of Orbits," by Professor Greenhill. 



ROYAL INSTITUTION. 

 A LECTURE in French was given on Friday, May 18th, in the 

 theatre of the Royal Institution by M. Alphonse Renard, 

 LL.D., etc.. Curator of the Royal Museum of Brussels, 

 on the formation of volcanic rocks. By means of the 

 oxy-hydrogen light a large number of illustrations were 

 thrown on the screen, showing the progress of crystalli- 

 sation in vitreous rocks and the many curious forms they 

 assume, according to the degrees of heat or other cir- 

 cumstances present during their transformation from 

 amorphous matter to the crystalline states, into what 

 are known as crystallites. Other views showed lava in 

 surging activity, carrying along already long-formed 

 crystals, breaking, corroding, and melting. After the 

 limit of the power of observing with the naked eye had 

 been reached, the microscope was brought in to reveai 

 the minutest details of the admirable texture of the vol- 

 canic masses. The lecturer explained the means by 

 which Sir James Hall, Gregory Watt, Fouque, Michel 

 Levy, and other experimenters were able to develop all 

 the required degrees of temperature, from dark red to 

 blinding white, and to maintain the temperatures for 

 indefinite periods. In spite, he said, of the splendid 

 achievements of synthetical geology, success was still 

 incomplete. Rocks containing mica, quartz, hornblende. 



