i8o 



NA TURE 



{June 23, 1 88 1 



of the two lines] in one spectrum is brought [directly over the 

 other in the otlier spectrum. The photometric parts included a 

 Nicol capable of rotation, a right and left rotating double 

 quartz, and a fixed Nicol. The mean value of the ratio sought, 

 from mea>urements on threed.iys, was i'6o ± o'Oi ; the probable 

 error of an observation being i 0*032. 



The amount of electric expansion in caoutchouc has been 

 investigated by Herren Korteweg and Julius {Wkd. Ann. 

 No. 4). They used tubes of white vulcani.sed caoutchouc made 

 insulating in water by being kept twenty-four hours in oil ; the 

 tube was filled with water and placed in a water-bath (to form a 

 condenser), while hydrostatic pressure was varied, and the 

 changes of volume were measured by means of a connected 

 tnbe-system. The change of volume is shown to be propor- 

 tional to the square of the striking distance, and inversely pro- 

 portional to the square of the thickness of tube-wall. It is the 

 same whether the inner liquid be charged negatively or positively. 

 The maximum was reached when the Holtz machine, left to 

 itself, gradually slackened sjjeed till the last spark passed. A 

 table, giving also Quincke's data for glass, shows that both for 

 this and for caoutchouc the volume-changes are, roughly speak 

 ing, in inverse ratio of the coefficients of elasticity, so that they 

 must be ascribed to the same cause. 



UNIVERSITY AND EDUCATIONAL 

 INTELLIGENCE 



Cambridge. — During the Long Vacation there will be ^ 

 course of lectures in the University Laboratory by Mr. Fenton' 

 one of the L'emonstrators, on Organic Chemistry. The Laboratory 

 will be r.pen for practical work. 



During the Michaelmas Term there will be twelve courses of 

 lectures on Chemistry and various branches of Physics, including 

 one by Mr. Shaw on the Conservation of Energy and Theory of 

 Unitation, and a course by Prof. Lewis on the more Common 

 Mineral Kock-Constituents, and another on Descriptive Crystal- 

 lography by the same. 



Prof. Dev\ ar's subject will be Physical Chemistry ; and among 

 other advanced lectures will be a course on the General Principles 

 of Chemistry by Mr. Pattison-Muir. 



Prof. Hughes and Mr. Tawney will divide between them the 

 work in Geology, Mr. Tawney takmg Pateontology in the 

 Michaelmas Term. 



Lectures on Botany will be given by Messrs. J. W. Hicks, 

 Vines, Saunders, and Hillhone. Dr. Vines' lectures in the 

 Michaelmas Term will be nn the Physiology of Plants, with 

 practical work, at Christ's College. 



Prof. Newton and the Demonstrator of Comparative Anatomy, 

 Dr. Michael Foster, and his corps of lecturers. Prof. Humphry, 

 Mr. Creighton, and Mr. Balfour, will give their usual series of 

 lectures and demonstrations during the Michaelmas Term. Mr. 

 Lea will give advanced lectures on Digestion and Chemical 

 Physiology, and Mr. Langley will lecture on the Histology and 

 Physiology of Muscle, Nerve and the Nervous System. 



Dr. Bradbury will lecture on Pathological Anatomy, Prof. 

 Latham on General Therapeutics, Prof. Paget on Clinical Medi- 

 cine, and Mr. Carver on Clinical Surgery. 



The Natural Sciences Tripos, Part L, under the Old Regula- 

 tions, has just been completed, and the pass-list contains the 

 names of thirty- three men, and three are excused the General 

 Examination. The second part of this e.xamination takes place 

 In December. 



The first part of the examination under the New Regulations, 

 by which men can enter for the examination in their second year 

 if they prefer, has just resulted in the publication of a list with 

 five names, in alphabetical order, in the first division, viz. Mesprs. 

 Daniels (Trinity), Duncan (Caius), Earl (ChrLst's), Sherrington 

 (Cams), and Wilberforce (Trinity). 



The special examinations in Natural Science for the ordinary 

 B.A. degree have yielded seven men in the first class in Chemis- 

 try, and eighteen in the second class. In Geology there was 

 but one man in the first and one in the second class ; in Botany, 

 one in the first class ; in Zoology, one in the second class. 



At Trinity College the prizemen in the June examination in 

 Natural Science were : Thir 1 year, Hillier and Ritchie ; second 

 year, Daniels and Wilberforce; first year, Davis, Head, Ran- 

 som, Thompson. The prizemen at Christ's College are Shipley 

 (first year). Earl (second year), and Parkyn (third year). 



The Chancellor of the University (the Duke of Devonshire) 



has (with the concurrence of Earl Cairns, Chancellor of the 

 University of Dublin) declared that the statutes of Cambridge 

 do not preclude the University from using the Previous and tlie 

 Tripos Examinations for the purpose of testing the proficiency 

 of women, as sanctioned by the Senate on February 24, 1881. 



SOCIETIES AND ACADEMIES 

 London 



Royal Society, May 19.— " Molecular Magnetism," by 

 Prof. D. E. Hughes, F.K.S. 



I. Influence of an Elastic Torsion upon a Magnetic or an 

 Electric Conducting Wire. — In my paper of March 7th on 

 " Molecular Electro- Magnetic Induction," I showed that induced 

 currents of electricity would be induced in an iron wire placed 

 on the axis of a coil through which intermittent currents were 

 pasing, and that these currents were produced only v\ hen the 

 wire was under the influence of a torsion not passing its limit of 

 elasticity. It became evident that if the intermittent magnetism 

 induced by the coil produced under torsion intermittent currents 

 of electricity, an intermittent torsion under the influence of a 

 constant current of electricity or a constant magnetic field would 

 produce similar currents. This was found to be the case, and 

 as some new phenomena presented themselves indicating clearly 

 the molecular nature of the actions, I will describe a few of 

 them directly relating to the subject of this paper. 



The apparatus used was similar to that descril ed in my paper 

 of March 7th. An iron wire of 20 centims. was placed in the 

 centre or axis of a coil of silk-covered copper wire, the exterior 

 diameter of the coil being 5i centims., having an interior vacant 

 circular space of 34 centims. The iron wire is fastened to a 

 support at one end, the other passing through a guide, to I eep 

 it parallel but free, so that any required torsion may be given to 

 the wire by means of a connecting arm or index. A sensitive 

 telephone is in direct communication with the coil, or a galvano- 

 meter may be used as the currents obtained by a slow elastic 

 torsion are slow and strong enough to be seen on a very or(linai7 

 galvanometer. I prefer, however, the telephone, because it has 

 the int estimable advantage in these experiments of giving ihe exact 

 time of the commencement or finish of an electric current. It 

 has, however, the disadvantage of not indicating the force or 

 direction of the current; but by means of the ^onometer the 

 true value and direction of any current is 'at once given. The 

 current from a battery of two bichromate cells is sent constantly 

 through the wire if we wish to observe the influence of the 

 torsion of the wire upon the electric current, or a constant field of 

 magnetic energy is given to the wire by either a separate coil or 

 a permanent magnet. The currents obtained in the coil are 

 induced from the change in the molecular ■magnetism of the 

 wire, but we may equally obtain these currents on the wire itself 

 without any coil by joining the telephone and rheotnme direct 

 to the wire ; in the latter case it is preferable to join the wire to 

 the primary of a small induction coil, and the telephone and 

 rheiitome upon the secondary, as then the rheotome does 

 not interrupt the constant electric current passing through the 

 wire. As the results are identical, I prefer to place the telephone 

 on the coil first named, as the tones are louder and entirely fi-ee 

 from errors of experimentation. 



If ve place a copper wire in the axis of the coil we produce 

 no efi'ect by torsion, either w hen under the influence of a constant 

 magnetic field or a current passing through it, nor do we i>erceive 

 any effects if we place an iron wire (2 millims. in diameter), 

 entirely free from magnetism, and throui.h which an electric 

 current has never passed. I mention this negaiive experiment in 

 order to prove that all the effects I shall mention are obtained 

 only through the magnetism of the wire. If now I pass an 

 electric current for an in-tant through this sn me wire, itsmilecules 

 are instantly polarised, and I have never yet been able to restore 

 the wire to its original condition, and the magnet isatie.n induced 

 by the 1 assage of a current is far mc^re powerful and more 

 persistent in soft iron than tempered steel. This may he due, 

 however, to the fact that in tempered or softened steel we find 

 traces only of a current during the rotation by torsi' in of its 

 molecules some two to three degrees of sonometer, whilst iron 

 gives constantly a current of 70 sonometric degrees.^ 



In order to obtain these currents, we must give a slight 



torsion of 5° or IC to and fro between its zero point. We then 



have a current during the motion of the index to the right, and 



a contraiy current in moving the index to the left. If w e use a 



, _ ' o'S of a Daniell batterj'. 



