262 



NA TURE 



July 12, 1906 



Chemical Society, June 21.— Prof. R. Meldola, F.R.S., 

 president, in the chair. — The Cleve memorial lecture : 

 I'rof. T. F,. Thoi-pe. — The constituents of the essential oil 

 Ironi the fruit of Pitlosporum undulatum : F. B. Power 

 and F. Tutin. The results show that the oil contains 

 iJ-pinene, d-limonene, esters of valeric, formic and other 

 acids, a sesquiterpene, palmitic acid, and a phenol. — Mo- 

 bility of substituents in derivatives of /3-naphthol : J. T. 

 Hewitt and H. V. Mitchell. — The decomposition of nitro- 

 cellulose ; O. Silberrad and R. C. Farmer. The de- 

 composition products are elhyl nitrate, ethyl nitrite, ethyl 

 alcohol, nitric and nitrous acids, ammonia, formic, acetic, 

 butvric, dihydro.xybutyric, oxalic, tartaric, isosaccharinic, 

 and hydroxypyruvic acids. Carbohydrates were also pre- 

 sent. — Note on gunpowder and bullets made about 1641, 

 recently discovered in Durham Castle : O. Silberrad and 

 W. S. Simpson. The gunpowder was found lo approxi- 

 mate closely in composition to the black powder now used 

 in this country. The ingredients had been merely ground 

 and mixed together. It seems probable that this powder 

 was of Prussian origin. — The constitution of acetone : 

 Miss M. Taylor. The results prove that acetone does not 

 behave either towards sodium or Grignard's reagent as iso- 

 propenylalcohol,CH,.C(OH) : CH,.— Diazo-derivatiyesof the 

 mixed aliphatic aromatic m-benzene-sulphonylaminobenzyl 

 amines ; G. T. Morgran and Miss F. M. G. Mickle- 

 thwait. — Influence of substitution on the formation of 

 diazoamines and aminoazo-compounds, part v. — s-Dimelhyl- 

 4 : 6-diamino-m-xylene : G. T. Morgan and A. Clayton. 

 — Improved apparatus for the determination of molecular 

 weights : P. Blackman. 



Linnean Socie'y, liine 21. — Dr. A. Smith Woodward, 

 F.R.S., vice-president, in the chair. — .\ contribution to the 

 botanv of southern Rhodesia : Miss L. S. Gibbs. The 

 collections on which the report was based were obtained 

 in August to October, 1905, at the end of the dry season. 

 The air is dry and the sun's rays very strong, temperature 

 from 80° to 90°, so that the country presented a burnt-up 

 aspect, and the trees were bare, except a few evergreens. 

 The veld is systematically burnt, to promote young growth 

 for cattle-food, to the detriment or destruction of trees 

 and shrubs. Distribution of species is wide, and the pre- 

 sent paper tends to a confirmation, with many new records. 

 Twenty-three new species are described, amongst the more 

 interesting being the grass Erianihus teretifolins, Stapf, 

 and a characteristic Elephantorhiza. — The authentic por- 

 traits of Linnffus : \V. Carruthers. The author recalled 

 the fact that in iSSg he made the subject the chief topic 

 of his address at the anniversary meeting on May 24 of 

 that year ; he subsequently visited Sweden, Germany, and 

 the Netherlands to inspect the originals, and read a paper 

 detailing his results at the general meeting held on 

 November 19, 1891 ; a transcript of his remarlcs had been 

 prepared, but did not satisfy him, and nothing was pub- 

 lished. The approaching bicentenary celebration of the 

 birthday of Linnjeus, for which the Swedes have been 

 mailing extensive preparations, had induced him to revise 

 his old transcript, and add some recently ascertained facts, 

 which he now submitted to the society. — Plants novae 

 Daweanae in Uganda lectse : Dr. Otto Stapf. Mr. M. T. 

 Dawe, officer in charge of the Forestry and Scientific De- 

 partment of the Uganda Protectorate, made an expedition 

 from Entebbe, through Buddu and the western and Nile 

 provinces of that territory. His collections were trans- 

 mitted from tiine to time to Kew, and his report was 

 issued as a Blue-book (1906, Cd. 2904) last April ; it gave 

 an account of his journey, with some rough illustrations 

 of specially noteworthy plants. Much new light is thrown 

 on distribution, and new species are described, amongst 

 them the new genus of Rutacea^, Balsamocitrus, Stapf, 

 and a new species of Warburgia (Canellaceae). As an 

 appendix, Mr. Dawe gives a summary of his report on the 

 vegetation of the country traversed. — The genitalia of 

 Diptera : J. Hopkinson. — The structure of bamboo leaves : 

 Sir Dietrich Brandis. 



Physical Society, June 22. — Prof. 1. Perry, F.R.S., 

 president, in the chair. — The effect ot radium in facilitating 

 the visible electric discharge in vacuo : A. A. C. Svwinton. 



NO. I 91 5, VOL. 74] 



It has been shown by Edison, Fleming, and others that 

 the passage of the electric discharge in vacuo is much 

 facilitated by heating the kathode. More recently it has 

 been shown that the passage of the discharge is still further 

 facilitated by coating the heated kathode with oxides of 

 the alkaline metals. It is generally held that the efficacy 

 of the hot oxides in this direction is due to their giving 

 off negatively-charged ions or corpuscles. The author 

 therefore decided to ascertain whether similar effects could 

 be obtained by painting the kathode with radium, and as 

 radium gives off corpuscles when cold, it was anticipated 

 that it might not be necessary to heat the kathode. 

 Using a continuous current up to 400 volts pressure, this 

 was found not to be the case, the radium having no 

 appreciable effect in producing a visible discharge. When 

 the radium-coated kathode was heated to redness, the 

 radium was found to have a very marked action in facili- 

 tating the production of a luminous discharge. Experi- 

 ments were made which proved that the mere presence of 

 radium in the tube was insufficient to produce the effect, 

 and, furthermore, it was found that the tube would only 

 allow visible discharges to pass in the direction that made 

 the radium-treated electrode the kathode, the tube acting 

 as a unidirectional valve in the same way as do tubes with 

 kathodes coated with oxides. — The effect of the electric 

 spark on the actinity of metals : T. A. Vaughton. It has 

 been pointed out by several observers that some metals, 

 such as aluminium, cadmium, zinc, magnesium, &c.. 

 although not radio-active in the ordinary sense of the 

 word, yet have the power of affecting a photographic plate. 

 The electric spark has a remarkable influence on this 

 *' actinity," in some cases causing an increase, and in 

 others ^ apparently diminishing it. The alteration is not 

 inerely momentary, but remains for months. It is, how- 

 ever, quite superficial, and may be removed by slightly 

 rubbing the surface of the metal with emery-paper. In 

 the case of aluminium sparked with gold, the direction of 

 the current does not make much difference in the actinity 

 of the sparked plate, but in the case of other couples the 

 difference is very marked. For example, if a cadmium 

 strip is sparked with antimony, the cadmium being con- 

 nected with the positive terminal, the cadmium becomes 

 very active photographically, not only on the spot sparked, 

 but all over its surface. If, however, the cadmium is 

 connected with the negative terminal and sparked with a 

 positive terminal of antiinony, the cadmium remains very 

 slightly more active than if not sparked at all. — The 

 dielectric strength of thin liquid films : Dr. P. E. Shaw. 

 The range of voltage used in the experiments is from 25 

 to 400, and the corresponding spark-lengths vary from 

 about 015 fi to 60 fi (fi = oooi mm.) for the insulating 

 liquids used. The apparatus employed for measuring 

 length is the micrometer designed by the author for 

 measuring gauges fProc. Roy. Soc, April). The sub- 

 stances used were olive oil, castor oil. linseed oil, rape oil, 

 turpentine, fusel oil, oil of resin, cod-liver oil, neat's-foot 

 oil, paraffin, transformer oil, the homologous series 

 C,H,„ C„H,,, C.H,j, C.H,„ and armacelC ohmaline, 

 and Sterling varnishes. The best insulators are paraffin 

 and transformer oil, though for these, as for all commercial 

 oils, great care was taken to remove water and acid by 

 prolonged heating to 110° C, and treating with potassium 

 carbonate. No simple connection can be traced between 

 specific inductive capacity and dielectric strength. — The 

 effect of electrical oscillations on iron in a magnetic field : 

 Dr. W. H. Eccles. In attempting to make precise 

 measurements of the effect of high-frequency oscillations 

 on iron held magnetised by a magnetic field, two main 

 difficulties are met. The one is that arising from the fact 

 that the oscillatory currents induced on the surface of the 

 iron investigated shield the inner layers, and thus make 

 the mass of iron affected a variable quantity. The other 

 difiiculty arises in the matter of producing oscillations of 

 determinate and invariable character. The author has 

 endeavoured to meet the first difficulty by using oscillations 

 so feeble that they affected only the outermost layers of 

 the iron wires employed, and these even only slightly. 

 The second difficulty has been met by using the oscillations 

 produced in an open insulated solenoid by a single small 

 measLu'able spark passed to one end of the solenoid. 



