46 



.\'. V TL R1-: 



[May 9, 1895 



iir expelled by the magnet, accunling !•> the pole that »tis 

 within the ring, which showed the existence of an electric 

 current prodiiceil liy the influence of the current in the conduct- 

 ing wire. Veritct, when dc^ribing the atwve ex[ierinient, falls 

 into a curious error. He says the apiwratus consisted of a 

 ring of tine copper « ire. susj>cnde<l by a silk thread in front of 

 the piDle of an electromagnet in such a way that the plane of 

 the ring was parallel to the plane of the turns of wire on the 

 electromagnet. On " making ' the current the ring is said to have 

 been repelled, but this deviation did not jiersist, and on *' break- 

 ing" the current the ring was attracted, also only momentarily. 

 Mr. Blakesley did not feel quite confident th.at in \'erdet's 

 form of the experiment there could ever be attraction. He 

 also pointed out that with an alternating current the disc would 

 tend to set itself parallel to the lines of force of the electro- 

 magnet. With reference to repulsion by alternating currents 

 in one of Elihu Thomi>s<in's experiments where a sphere is 

 supported over an alternating (xile, a screen being placed so as 

 to partly shield this sphere, there is generally a misstatement 

 as to the direction in which the sphere rotates. It 

 rotates in .such a direction that the part of its surface next the 

 magnet moves towards the edge of the screen. Dr. Burton 

 said that from the fact that when the current in the electro- 

 magnet in \'erdet's ex|)eriinent is broken, the induced current 

 in the ring is in the same direction as the current in the 

 magnet, the ring will be attracted. Mr. Boys confirmed Dr. 

 Burton's statement. lie recommended setting the ring at an 

 angle of 45' to the lines of force, under which circumstances a 

 rotation would be obtaineil. .\ distinction must, he pointed out, 

 be drawn between .such an exiwriment as that of Verdet and 

 those of Elihu Thompson. The repulsions observed in these 

 latter were only due to the " l;ig " in the induced currents caused 

 by self-induction. The bc>t materials to use for all such experi- 

 ments were magnesium and aluminium, since for a given mass 

 these had the highest conductivity. — Mr. VV. G. Kho<les read a 

 |«per entitled "A theory of the .Synchronous Motor." The 

 object of this paper is to give as sim|>le a treatment as possible 

 of the mathematical |xirt of the subject, and to give theoretical 

 proofs of some experimental facts. Starting from the energy 

 equation 



/ -4- r- R = r E cos ■^ 



where/ is the output of the motor, k the resistance of the arma- 

 ture, < the current through the armature, E the E.M.K. applied 

 to the motor terminals, anil i( the phase diflference between i" and 

 E the ca.ses of maximum rmtput, zero out[Hit, minimum current 

 at jero (xiwer, and maximum phase ilifference between i and E 

 are considered. The.se results are, for the most part, obtained 

 directly from the energy e<)ualion. The latter part of the paiK-r 

 Is devoted to a discussion of the pha.se relationships Ijetween the 

 current and the E..M.E.S in a plant con.si.sting of a generator and 

 motor, and to the variations m the armature reactions in both 

 generator and motor. .\ theoretical proof is given of the fact, 

 oljscrved by f'rof. .Silvanus Thompson and others, that an over- 

 excited synchronous motor acLs as a condenser, and tends to 

 make the current leail lieforc the generator's E.M.K. I'rof. 

 .S, P. Thomi)vm said that the mathematical |>artof the paper was 

 much .simpler than that in previous investigations on this subject, 

 and the metho<l of arriving at the results by rejecting imaginary 

 r<x>ls of the equatii>ns was particularly neat and inslnictive. 

 The part of the paper relating to armature reactions and pha.se 

 rclationshi|is was quite new. Two results deserved special 

 attention : first, that the maximum current at zero power Wiis 

 the same as if the circuit was non-inductive ; second, that the 

 iruximum current 7.cro (lower Wiis double the current correspond- 

 ii' inim output. Mr. Blakesley .said that the iwper did 

 " 'he stability of the .system, and he thought some of 



' rres|>onile(l to regions of imstabilily. — .\ pa|KT by 



^' On a simple graphical interpretation of the deter- 



iiM ition of dynamics," was, in the absence of the 



•lullmr, read by Dr. Burton. The rekation is worked out for two 

 s(»vi.i||y Mmple systems |>os.sessing erne degree of freedom : (I) a 

 I'" ing in a straight line with uniform acceleration; 



' -' moving to and fro ahmg a straight line with an 



•«.■•. Li., Iirected towards a fixed point im the line, and pro- 

 portioned to the distance from that [Kiinl (simple harmonic 

 motion). On conslruriing a iliagram in which the ab.sci.vv-e re- 

 IwcMnt values of the single rwirdinate of the particle, and the 

 >ir(Iinate'» corresponding values of the momentum, the deter- 

 tninanlal relation Iiecomes equivalent to the constancy of the 

 area ■•f a certain elementary parallelogram. In case (I) this 



NO. 1332, VOL. 52] 



|V»rallelogram moves along a parabola, experiencing a shear as 

 it goes, while in case (2) there is no distortion, the (rectangular) 

 parallelogram revolving alniul the origin of the diagram as if 

 rigidly attachetl to an inextensible radius vector. 



Linnean Society, April 18. — Mr. C. B. Clarke, F.R.S., 

 President, in the chair. — In view of the approaching anni- 

 versary meeting, the election of auditors was made, when 

 Mr. A. 1). Michael anil Prof. J. K. Green were nominated on 

 behalf of the Council, and Messrs. E. M. Holmes and H. 

 Groves on behalf of the Fellows. — Mr. T. B. Blow exhibited 

 specimens of the river-weed Mouirra fliivuililis, -Aublet, from 

 the River Es.sequibo, with observations on its life-history, and 

 lantern slides illu.strating the natural haunts of the plant. — Mr. 

 J. E. Harting exhibited and made remarks upon a collection of 

 West African Lepidoptera which had been collected and for- 

 warded by .Mr. J. T. .Studley from Old Calabar, and «as to be 

 presented to the British .Museum. — Mr. 1 Inward Saunders exhi- 

 bited a si>ecimen of the European white-winged Crossbill, Loxia 

 bi/asciata, which had been shot in co. Fermanagh in February last, 

 and was lent for exhibition by Mr. C. Langham. — Some photo- 

 graphs of English Red-deer heads, showing successive g.-ov\ths 

 of antlers in the same stag by comparison of the sheii hortis, 

 were exhibiteil on behalf of Mr. Lucas, of Warnham Court, 

 Horsham. — .V paper was then read by Mr. !•". W. Keeble, 

 entitled "Observations on the Loranlhateit of Ceylon," in 

 which country the author had made a short sojourn in 1894. 

 .-Vfter remarking that in Ceylon many species of J.oniiil/.iis have 

 large and conspicut)iis tlowers, with the corolla-tube brightl)' 

 coloured, more or le.s,s tubular and lobeil, he pointed out that 

 certain deviatit>ns from the typical regularity of the corolla-tube 

 were correlated with the mode of fertilisation of the Hower b) 

 Sun-birds {AW/artm;,-), an<l this wius made clear by diagrams 

 and some excellent coloured drawings. Discussing the mode 

 of distribution of the seeds, Mr. Keeble first tjuoted the views 

 of Engler and Prantl, and the remarks in Kerner's " Pflan/.en- 

 leben " (English edition), on the tlisseminalion <if the European 

 .Mi.stletoe, and then detailed his own observations in the ca,se ol 

 tropical Lorauthait\c, The modes of germination of various 

 species of /.oran/hiis and I'isciim were then described, as well 

 as the curvature and growth of the hypocotyl, and the effect ol 

 contact on the Latter, and <m its suctorial disc ; the |iaper con- 

 cluding with some remarks on the forms of fruit and seed ol 

 Cinghalese species of l.oranthaicit. — .Mr. A. Trevor-Baltyi 

 exhibited .and made remarks upon a collection of plants obtaineil 

 during his sojourn on the Island of Ivolguev. 



Entomological Society, M.ay l. — Prof. Raphael Meklola, 

 F. R.S., President, in the chair. — Dr. C. G. Thomson, of the 

 University, Lund, .Sweden, w.as elected an Honorary Fellow, to 

 fill the vacancy in the list of Honorary Fellows cau.sed by the 

 death of Pxstor Wallengren. — Mr. Waterhouse exhibited a living 

 larva of a Longicorn Beetle. This larva was found in a boot- 

 tree which had been in constant use by the owner for fourteen 

 years, the last seven of which were s|)enl in India. The 

 specimen w;vs brought to the British Museum on May 6, 1890, 

 and was put into a blink of beech wood in which it h.ad lived 

 ever since ; it did not appear to have altered in any way during 

 the.se five years. It had burrowed about eight inches, and 

 probably made its exit accidentally. Mr. Blandford referred to 

 a similar ca,se which had come under his notice. -Mr. C. G. 

 Barrett exhibited a long series of the dark and strongly-marked 

 varieties of Ajp-olis cunoria and Aip-iilis Iritiii. taken on the sand- 

 hills of the north-easl coa.st of Scotland by Mr. .\rthur Home, 

 of .Mwrdeen. — Mr. Dale exhibited a s|K'cimen of a Sesia — 

 sujiposed to Ik.' a new species — from the New Eore.st. — Mr. O. E. 

 Janson exhibited a remarkable species of Ciiriii/ioiiiiiir from the 

 island of Gilolo, having exceedingly long and slender antennie 

 and legs ; it w.as apparently an undescribed species of the genns 

 7'itlitiilliiii, Pascoe. Mr. Nelson Richardson called attention to 

 a paper by himself, in the /'ro.ei-iiiii/;s of the Dorset Natural 

 History and Antiquarian Field Club, on the subject of Dorset 

 I^-pidoptera in 1892 and |893.--Mr. W. L. Di.st.ant com- 

 municated a [hiikt entitled. " On a probable explanation of an 

 unverified observation rel.ative to the family Fulgoridie." In the 

 discussion which ensued, Mr. Blandforil S.U1I he thought further 

 evidence w:ls required on the subjecl of the allegecl luniiiiosily in 

 the Fulgoriike before the statement contained in .Mr. Distanl's 

 pa|>er could be accepted. — Mr. J. J. Walker, R.N., contributed 

 a paper entitled, "A preliminary list of the Butterflies of 

 Hong-Kong, Uised on observations and captures made during 

 the winter anil spring months of 1892 and 1893.''- Prof. Meklola 



