Feb. lo, 1881] 



NATURE 



355 



Mr. Shaw on Heat. All these courses are given in the Cavendish 

 Laboratory. 



Prof. Stuart is lecturing on the Difterential Calculus and its 

 Application to Mechanics ; the Demonstrator has a course on 

 Elementary Applied Mechanics. 



Dr. Michael Foster continues his cour.se of Elementary Physio- 

 logy. The advanced lectures announced this term are by Mr. 

 Lea (who has been appointed Lecturer in Physiology at Gonville 

 ani Caius College), on Physiological Chemistry ; .Mr. Langley, 

 on the Histology and Physiology of the Dige.-tive System, and 

 Mr. Hill (Downing College), on the Central Nervous System. 



The Report of the Syndicate on the Higher Education of 

 Women is to be discussed tomorrow (February 11). 



The Board of Natural Science Studies recommends that the 

 agreement between the University and Dr. Dohrn, of the Zoo- 

 logical Station at Naples, by which 75/. per annum is paid from 

 the Worts Travelling Bachelors' Fund towards the expenses of 

 the station, be renewed for five years. The Board calls attention 

 to the services which those members of the University who have 

 studied at Naples have rendered to jcience and the University, 

 and to the fact that three of them have obtained professorships 

 elsewhere, namely Professors A. M. Marshall (Owens), T. W. 

 Bridge (Mason's College, Birmingham), and A. C. Haddon 

 (Dublin). 



At Newnham College Miss Harland is lecturing on Euclid 

 and Algebra, and Miss Scott on Analytical Conies, Mr. Ganiett 

 lectures on Statics and on E.\perimental Physics, Mr. Hudson 

 on Arithmetic and on the Differential Calculus, Mr. Hillhouse 

 on Botany, while Miss Cross superintends practical and paper 

 work in Chemistry and Geology. 



SOCIETIES AND ACADEMIES 



London 



Royal Society, December 9, 1880. — " The Electrostatic 

 Capacity of Glass," by J. Hopkinson, M.A., D.Sc, F.R.S. 



In 1877 I had the honour of presenting to the Royal Society 

 {Phil. Trans., 187S, Part i.) the results of some determinations 

 of specific inductive capacity of glasses, the results being ob- 

 tained with comparatively low electromotive forces, and with 

 periods of charge and discharge of .sensible dm-ation. In 1S78 

 Mr. Gordon (Phil. Trans., 1879, Part i.) presented to the Royal 

 Society results of experiments, some of them upon precisely 

 similar glas.se.s, by a quite different method with much greater 

 electromotive forces, and with very short times of charge and 

 discharge. Mr. Gordon's results and mine differ to an extent 

 which mere errors of observation cannot account for. Thus for 

 double extra dense flint glass I gave lo'l, Mr. Gordon 3'i, and 

 subsequently 3*89 (Report of British As Delation for 1879). 

 These results indicate one of three things, either my method is 

 radically bad, Mr. Gordon's method is bad, or there are some 

 physical facts not yet investigated which would account for the 

 difference. Two suggestions oocur : — I. Possibly for glass K is 

 not a constant, but is a function of the electromotive force. 2. 

 When a glass condenser is discharged for any finite time, a part 

 of the residual discharge will be included with the instantaneous 

 discharge, and the greater the time the greater the error so 

 caused. To test the first I measured the capacity of thick glass 

 plates with differences of potential ranging from 10 to 500 volts, 

 and also of thin glass flasks between similar limits ; the result is 

 that I cannot say that the capacity \^ either greater or less where 

 the electromotive force is 5000 volts per millimetre than where 

 it is 4 volt per millimetre. The easiest way to test the second 

 hypothesis is to ascertain how nearly a glass flask can be discharged 

 in an exceedingly short time. A flask of light flint gla's was 

 tested ; it was charged for some seconds, discharged for a time 

 not greater than T7j-jru second, and the residual charge observed 

 so soon as the electrometer needle came to rest ; the result was 

 that the residual charge under these circumstances did not exceed 

 3 per cent, of the original charge, also that it mattered not 

 whether the discharge lasted Tywtr second or jV second. These 

 experiments suffice to show that neither of the above supposi- 

 tions accounts for the facts. 



I have repeated my own experiments with the guard-ring 

 condenser, but with a more powerful battery, and with a new 

 key which differs from the old one, inasmuch as immediately 

 after the condensers are connected to the electrometer they are 

 separated from it. In no case do I obtain results differing much 

 from those I had previously published. 



Lastly, a rough model of the five plate induction balance used 



by Mr. Gordon was constructed, but arranged so that the 

 distances of the plates could be varied within wide limits. So 

 far as instrumental means at hand admitted Mr. Gordon's method 

 was used. A plate of double extra dense flint and a plate of 

 brass were tried. In the first, by varying the distances of the 

 five plates, values of K were obtained ranging from ij to 8j, 

 with the latter results from y'^ to 3. It is clear that the five 

 plate induction balance thus arranged cannot give reliable 

 results. 



The explanation of the anomaly, then, is that the deviation 

 from uniformity of field in Mr. Gordon's apparatus causes errors 

 greater than any one would suspect without actual trial. It is 

 probable that the supposed change of electrostatic capacity with 

 time may be accounted for in the same way. 



January 27. — "Dielectric Capacity of Liquids." By J. Hop- 

 kinson, F.R.S. 



These experiments have for object the determination of the 

 refractive indices and the specific inductive capacity of certain 

 liquids, and a comparison of the square of the refractive index for 

 long waves and the specific inductive capacity. 



In the following table are given the results obtained for 

 refractive index for long waves deduced by the formula 



(u = ^^ 4- — , the square of (U„, and the observed values (K) of 

 the specific inductive capacity. 



Petroleum spirit (Field's) I "922 ... I "92 



Petroleum oil (Field's) 2 "07 5 ... 2^07 



,, (Common) 2*078 ... 2'IO 



Ozokerit lubricating oil (Field's) ... 2'oS6 ... 2'13 



Turpentine (Commercial) 2'I2S ... 2*23 



Castor oil 2-153 ••■ 478 



Sperm oil 2'I35 ... 3'02 



Olive oil 2131 ... 3-16 



Neatsfoot oil 2-125 ■•■ 3'07 



It will be seen that whilst for hydrocarbons /ij^ = K, for 

 animal and vegetable oils it is not so. 



Zoological Society, February i. — Prof. W. H. Flower, 

 LL.D., F.R.S., president, in the chair.— Mr. F. M. Balfour, 

 F.K.S., read a paper on the evolution of the placenta and made 

 some observations on the possibility of employing the characters 

 of this organ in the classification of the mammals. — Mr. Sclater 

 read notes on some birds collected by Mr. E. F. im Thurn in 

 British Guiana, amongst which was an example of a new species 

 oi AgcLzus, proposed to be called/?. im-Thnrni, after its dis- 

 coverer. — Mr. W. T. Blanford, F.R.S., read an account of a 

 collection of reptiles and frogs made at Singapore by Dr. W. B. 

 Dennys. In this collection were two new species of Ophidians, 

 which were named respectively Cylindrophis lincitns and Simotes 

 Dennysi, and two new frogs, which the author proposed to call 

 Rana la'.iceps and Rhacophorus Dennysi. — Mr. A. F). Bartlett 

 read an account of a peculiar habit of the Darter [Plotus anhinga) 

 in casting up parts of the epithelial lining of its stomach, as 

 observed by him in the specimen now living in the Society's col- 

 lection. — A communication was read from Mr. A. Heneage 

 Cocks, F.Z.S., containing notes on the breeding of otters, as 

 observed by him in specimens living in his possession. — The 

 Secretary read a paper by the late Mr. Arthur O'Shaughnessy, 

 containing an account of a large collection of lizards made by 

 Mr. C. Buckley in Ecuador. The collection was stated to be of 

 great interest, both on account of the number of new species it 

 contained and the fresh material it afforded for the study of 

 species already known. Mr. O'Shaughnessy had given last year 

 a partial notice of this collection, confined however to a preli- 

 minary list of the species of A no/is identified. The present paper 

 gave the results of a study of the whole collection, and was not 

 restricted to a description of the new forms, but enumerated all 

 the species, for the purpose of recording additional remarks and 

 revisions which appeared necessary. In it twenty-seven species 

 were mentioned, ten of which were new. — Mr. G. A. Boulenger 

 read an account of a new species of Enyalins in the Brussels 

 Museum, from Ecuador, which he proposed to name Enyalius 

 0''Shaughncssyi.—V\e.\i\..-Qo\. II. H. Godwin-Austen, F.R.S., 

 read the first part of a memoir on the land-shells collected on the 

 island of Socotra by Prof. I. B. Balfour. The present communi- 

 cation comprised an account of the species of CyclostomaccT found 

 on the island. 



Photographic Society, January 11. — J. Glaisher, F.R.S., 

 president, in the chair. — Papers were read by E. Viles on the 



