April 17, 1890] 



NATURE 



575 



electro-dynamometers, wattmeters, &c. Assuming constant 

 period and constant moment of inertia about the axis of rotation, 

 it is shown that for zero instruments, the best shape of the section 

 is two circles tangential to the direction of the deflecting field at 

 the point about which the coil turns. A table accompanies the 

 paper, in which various forms of section are given, together with 

 their relative deflecting moments per unit moment of inertia ; 

 the coils being taken of equal lengths and the current density 

 constant. From this table it appears that ordinary D'Arsonval 

 coils only give about 45 per cent, of the maximum deflecting 

 moment, and ordinary Siemens' dynamometers from 40 to 53 

 per cent. The various assumptions made in the paper are shown 

 to be justifiable in commercial instruments, and the modifications 

 necessary in special cases are pointed out. Mr. C. V. Boys 

 said he had, when working at his radio-micrometer, arrived at a 

 shape similar to that recommended in the paper. He also 

 noticed a peculiar relation true for all shapes where the length 

 parallel to the axis of rotation is great compared with the breadth. 

 Suppose a coil of any dimensions, then another coil of half the 

 breadth and double the length and cross-section will be 

 dynamically, electrically, and magnetically the same as the 

 original ; for the moment of inertia, the electric resistance, and 

 the enclosed magnetic field are equal. The above relation is 

 also true when the breadth is not small, if the cross pieces be 

 thickened near the axis so as to make their moment of inertia 

 proportional to their length. He inquired whether the author 

 had considered the subject of grading movable coils ; he himself 

 was of opinion that, unlike fixed galvanometer coils, the wire 

 near the axis should be thicker than that further away. The 

 President remarked that in 1881 Prof. Perry and himself ex- 

 hibited a wattmeter at the Society of Arts, whose movable coil 

 somewhat resembled one of those in the paper, which gave a 

 deflecting moment of 95 per cent, of the maximum. In design- 

 ing the instrument they had felt that the ordinary method of 

 using a comparatively large swinging coil was not the best, and 

 this led them to the shape adopted. 



Entomologrcal Society, April 2.— Mr. Frederick DuCane 

 Godman, F.R.S., Vice-President, in the chair. — Mr. Godman 

 announced the death of Dr. J. S. Baly, of Warwick, the well- 

 known Goleopterist, who had been a member of the Society for 

 the last forty years. — Dr. Sharp exhibited and made remarks 

 on a female specimen of Temnochila quadricollis, Reitt., which 

 was the subject of a very unusual malformation of the nature 

 termed " ectromelie " by Lacordaire. — Mr. R. W. Lloyd ex- 

 hibited three specimens of Elater pomonce, taken at Brockenhurst 

 about the middle of March last. — Colonel Swinhoe exhibited, 

 and read notes on, a number of butterflies of the genus Etithalia. 

 He pointed out that the specimens described as a species by the 

 name of Euthalia sedeva were only the females of E. balarama. 

 — Mr. T. R. Billups exhibited male and female specimens of 

 Cecidomyia salicis-siliqua, Walsh, which had just emerged from 

 galls received from Mr. Cockerell, who had collected them on a 

 species of sallow in Colorado. He also exhibited three species 

 of IchneumonidiE new to Britain, viz. Ichneumon haglundi, 

 Holmgr. ; Phygadeuon rufo-niger, Bridg. ; and Phygadetion 

 sodalis, Tasch. — Mr. C. G. Barrett exhibited specimens of 

 Pryotropha ohscurella, Hein, and Doryphora elongella, Hein, two 

 species of Mic o Lepidoptera new to Britain. — Dr. Thallwit?:, 

 of Dresden, contributed a paper entitled " Notes on some 

 species of the genus Hilipus." These notes had reference to a 

 paper on the genus Hilipus, by Mr. F. P. Pascoe, published in 

 the Transactions of the Society for 1889. — Mr. E. Meyrick 

 read a paper entitled " The Classification of the Pyralidina of 

 the European Fauna." — Prof. Westwood communicated a paper 

 entitled "Notes on certain species of Cetoniidse." — Mynheer 

 P. C. T. Snellen, of Rotterdam, contributed a paper entitled 

 "A Catalogue of the Pyralidae of Sikkim collected by H. J. 

 Elwes and the late Otto MoUer," and Captain Elwesread notes 

 on the foregoing paper as an appendix. Mr. W. L. Distant, 

 Colonel Swinhoe, Mr. McLachlan, and Mr. Jacoby took part in 

 the discussion which ensued. 



Zoological Society, April i.— Dr. A. Giinther, F.R.S., 

 Vice-President, in the chair, — The Secretary read a report on 

 the additions that had been made to the Society's Menagerie 

 during the month of March 1890 ; and called special attention 

 to a fine example of a rare Passerine ^vcA\Hypocolms amplmus) 

 from Karachi, presented to the Society by Mr. W. D. Gumming, 

 Curator of the Museum, Karachi ; and to two Mantchurian 



Cranes (Grus viridirostris), presented to the Society by 

 Mr. C. W. Campbell, of H.B. M.'s Consular Service, Corea. 

 — Mr. J. H. Gurney, Jun., e.\hibited and made remaiks on a 

 hybrid between the Tree-Sparrow (Passer montanus) and the 

 flouse- Sparrow {P. domestict(s), bred in captivity at Norwich. — 

 Mr. W. B. Tegetmeier, exhibited a specimen of a Greek Par- 

 tridge, shot in the Rhone Valley, and of an abnormal Viper. — 

 Mr. A. Smith- Woodward exhibited and made remarks on a 

 specimen of a Mesozoic Palaeoniscid Fish from New South Wales, 

 and pointed out that the structure of its pelvic fins seemed to 

 confirm the recent opinion that the Palaeoniscidae are related to 

 the Acipenseridae and not to the Lepidosteidse. The author be- 

 lieved the specimen exhibited to be the only one of the kind in 

 existence. — Mr. C. M. Woodford made some remarks on the 

 fauna of the Solomon Islands ; and exhibited a large number of 

 photographs in illustration of his remarks and of his recent ex- 

 plorations in these islands. — A communication was read from 

 Dr. R. W. Shufeldt, entitled " Contributions to the Study of 

 Helodernia suspectum," containing a complete account of the 

 osteology and anatomy of this venomous Lizard. A list of the 

 literature on the subject was added. — Dr. A. Giinther, F. R.S., 

 read the descriptions of new species of Deep-sea Fish from the 

 Cape {Lophotes fiski), based on a specimen sent to the British 

 Museum by the Rev. G. H. R. Fisk. — Mr. Edgar A. Smith, 

 read a report on the Marine Molluscan Fauna of the Island of 

 St. Helena, based principally on a large series of specimens 

 collected by Captain Turton, R.E., and presented to the British 

 Museum. — A second paper by Mr. Edgar A. Smith contained 

 a report on the Marine Mollusca of Ascension Island. 



Mathematical Society, April 3.— J. J. Walker, F. R.S., 

 President, in the chair. — The following communications were 

 made : — On the properties of some circles connected with a 

 triangle formed by circular arcs, by Mr. Lachlan. — Some pro- 

 perties of numbers, by Mr. Christie. — The modular equations 

 for « = 17, 29, by Mr. R. Russell. Communicated by Prof. 

 Greenhill, F.R.S. 



Edinburgh. 



Royal Society, March 17. — Sir W. Thomson, President, in 

 the chair. — The President read a paper on an accidental illustra- 

 tion of the effective ohmic resistance to a transient electric 

 current through an iron bar. — Prof. C. Michie Smith read a 

 paper on the absorption spectra of certain vegetable colouring 

 matters, the most interesting of which was a green colouring 

 matter extracted from the pulp surrounding the seeds tricosanthes 

 palmata. This substance is not chlorophyll, but is allied to it. 

 —Prof. Smith also described a method of determining surface 

 tensions by measurement of ripples. Ripples are set up on the 

 surface of the liquid by means of a tuning-fork and the surface 

 is then photoj^raphed along with a suitable scale. The lengths 

 of the ripples can thus be obtained by micrometric measurements 

 of the negative. The results obtained for mercury were very 

 concordant, andagreed with the mean value obtained by Quincke. 

 Strong electrification of the surface was found to reduce the 

 value of the surface tension by more than 20 per cent. A few 

 measurements of the surface tension of water also gave very fair 

 results. — The Hon. Lord M'Laren read a paper on the solution of 

 the three-term numerical equation of the «lh degree. — The Presi- 

 dent read a paper, illustrated by a model, on a mechanism for 

 the constitution of ether. 



Pa:iis. 



Academy of Sciences, April 8. — M. Duchartre in the 

 chair. — M. Maurice Levy, in a note on theories of electricity, 

 shows that the formula given in his communication on March 17, 

 representing the action between two moving electric particles, 

 includes all the theories of electricity yet proposed, and that the 

 values of an arbitrary constant required to satisfy each of the 

 known theories are none of them competent to explain the move- 

 ment of the perihelion of Mercury, whereas the latter is com- 

 pletely in accordance with the formula when another suitable 

 value is chosen for the constant. — M. R. Lepine, in a note on 

 the normal presence in chyle of a ferment destroying sugar, 

 suggests that in the majority of cases of diabetes the disease is 

 probably due to a defect in the production of this necessary 

 body. — Observations of Brooks's comet (a 1890), made with the 

 great equatorial of Bordeaux Observatory, by MM. Rayet, Picart, 

 and Couriy. The comet was observed on March 30 and 31, and 



