38 



NATURE 



[May 9, 1895 



by turning on or off any part, or the whole of the current. Electri- 

 cally heated hot-plates, flat-irons, and radiators were shown con- 

 ^^ruclcd on the same principle. Mr. Crompton also exhibited 

 ihe latest form of Crompton potentiometer, for ratio measure- 

 ments (accuracy I in 1,000,000), and simple forms of platinum 

 thermometers for use with potentiometer. 



A new instrument for testing the quality of iron in regard to 

 magnetic hysteresis was exhibited by I'rof. Ewing (Fig. I). Its 

 ^Iiecial use is to test sheet-iron for transformers and dynamo 

 armatures. A few strips of the iron to be tested are cut to the 

 length of three inches. These are clamped in a carrier, which 

 is then caused to revolve between the poles of a magnet. The 

 magnet is susjiended on a knife-edge, and becomes deflected in 

 consequence of the work exixnded in overcoming the magnetic 

 hysteresis of the sample. The deflection is observed by means 

 of a pointer, and serves .is a measure of the hysteresis. The 

 apparatus is so designed as to make the induction nearly the 

 same in all specimens, notwithstanding differences of perme- 

 ability. This makes its indications .strictly a test of hysteresis. 



Mr. L. Pyke showed an arrangement by means of which it is 

 possible to obtain a greater efticiency in the retiuction of the 

 highly electro- |X)sitive metals from aqueous solutions, into and 

 forming an amalgam with a mercury cathode. 



.\ system of electric meters, viz., voltmeters, ammeters, and 

 wattmeters, suitable for either direct or alternating currents, 

 formed Major Holden's exhibit. 



Prof. George I"ort>es exhibited a torsion model of submarine 

 cable. A thread vertically suspended in oil represented the 

 cable; the torsion (E.M.K.) Iwing applied at the top by vanes 

 and a p<jsitive or negative air blast (battery). The whole 

 was suspended at the top by a spring (sending condenser) : at 1 

 the bottom was a mirror to reflect spot of light. This was con- 

 trolled bv a magnet (receiving condenser). Fluid friction repre- 

 sented resistance. Twist represented charge. The model gave 

 signals com|)ared with those of a cable 2000 miles long". 



Specimens of the de|xisil or incrustation on the insulators of 

 the electric light mains at St. Pancras, in which metallic sodium 



and pola-ssium have lieen found, and of the insulators and wood 

 Ijearcrs, which were in use on these mains, were exhibited by 

 Major ("ardcw. K.K. The deimsil w.xs found to have ln-en 

 caused by the |>a.v<aj;i- of alkaline salts in solution to the negative 

 main, the sails U-ing chiefly derived from the neighlKUiring soil, 

 with which Ihe end fibres of the wood bearers were in contact. 



Electrolysis of these salts took place with liberation of the 

 metals at the negative main, the metals being oxidised and 

 slowly carbonated in air. During this process nodules of the 

 metal seem to have become embedded in the oxides, and 

 preserved from oxidation. 



Mr. Francis Galton showed enlarged finger prints, with de- 

 scriptive notation, and a print of the hand of a child eighty- 

 six days old. 



I'rof. J. B. F'anner had on view examples of helerotypical 

 nuclear division in repro<hictive ti.ssues of plants. 



Microscopic specimens illustrating some appearances of nerve- 

 cells were exhibited by Dr. Gustav .Mann ; and wandering cells 

 of the intestine were shown by Dr. VVesbrook and Mr. W. K. 

 Hardy. 



Mr. W. T. Burgess showed the results of experiments in 

 connection with the transmis.sion of infection by flies. Flies 

 having l)een placed in momentary contact with a cultivation of 

 Baiilliis prodigiosHS (or other suitable chromogenic organism) 

 were allowed to escape into a large room, .\fter some lime they 

 were recaptured and caused to walk, for a few seconds, over 

 slices of sterile potatoes, which were then incubated for a few 

 days. The experiments showed that the tlie>' Iracks on the 

 potatoes were marke<l by vigorous growths of the chromogenic 

 organism, even when the flies spent several hours in ct)nslanl 

 activity before they were recaptured. The use of pathogenic 

 organisms in these experiments would be attemled with obvious 

 dangers, but the results obtained with harmless microbes indicated 

 the constant risks to which flies expose us. 



Prof, f.otch and Dr. II. O. Forbes showed a living speci- 

 men of the Malafterurus cicilriiiis from the River Senegal ; 

 .Mr. Stanley Kent, a new b.icterial species: and Mr. D. Sharp, 

 K.R.S., examples of variation in the size of beetles. In some 

 beetles there is great difference in the size of adult individuals of 

 the same species and sex. In one of the ca.ses exhibited— 

 /ireiithiis aiuliorago — this difference was, in length alone, nearly 

 as five .ind one. It is believeil that these extreme ca.ses occur 

 chiefly in forms in which ihe males are ornamented with 

 "useless" appendages, e.g. the families Scarabaid;e, Lucanid.X', 

 Brenthidx. 



The exhibit of the Marine Biological .Vssociation consisted of 

 (l) marine organisms preserve<l in formic aldehyde, which, in 

 dilute solutions, is specially useful for the preserv.ition of trans- 

 parent organisms as nniseum specimens : (2) a new method of 

 fixing methylen-blue preparations. The methylenblue |>repara- 

 tions are fixed wilh amniunium m<>lyl>date. I'his method, due 

 to Dr. Berthe, of Berlin, has the advantage of retaining the 

 original blue colour of the preparations, and also of allowing the 

 object to be mounted in Ixilsam. or imbeddeil in paraffni in the 

 usual way ; (3) the action of light on the under siiles of flat 

 fishes. The flat fishes exhibited were reareil in a lank wilh a 

 flat slate boUom and glass from. Those porlions of the under 

 side of a fish which were nol in conlacl wilh the slale. and to 

 which light wasaccessilile— this point being demonstrated by the 

 expi>sure of a photographic ))lale upon which ihe fish lay — have 

 beccmie pigmented, whilst the remaining porlions are wilhoul 

 pigment ; (4) living repre.sentalives of ihe Plymouth fauna. 



.A gradient indicator was exhibited by Mr. |. Wim.shursl ; 

 and Sir Benjamin W. Richardson showed an electrical cabinel, 

 for use in the wards of a hospilal. 



There were only two astronomical exhibits. Mr. J. Norman 

 Lockyer, C.B., showed an enlargement of a photograph of the 

 .spectrum of a Ononis, taken with a 6-inch telescope and an objec- 

 tive prism of 45'. 



Mr. Sidney Waters exhibited charts showing ihe distribution 

 of the nebulx and slar-clusters, and their relation to the Milk) 

 Way. These charts, ujion which are recorded ihe posiuoii •■! 

 the 7840 objects of the New General Catalogue of iSSS, were 

 designed to show the distribution of the nebuke and star-clusters, 

 more es|K-cially in relation to the Milky Way. The resoluble 

 and irresoluble nebula- are shown to be most densely .scattered 

 in the poles of the gakictic circle, ami avoid the track of the 

 Milky Way, while Ihe star-clusters follow its course willi great 

 fidrlily. The evidence derived from this distribution seems lo 

 point lo scmie general cimneclion between Ihe nebular system and 

 Ihe system of the stars. 



Prof. Rainsjiy had a spectroscope and Pliicker tubes arranged 

 to give ocular demonstration of the spectra of argon exlracled 

 from air, and of a mixture of argon aiul helium extracted from 

 clevcile. Il is hardly neces.sary lo say that Ihe speclro.sco])e was 

 in great demand all the evening. 



NO. 1332, VOL. 52] 



