August 24, 1893] 



NATURE 



407 



ia<tu:lionte<i resistance; E, a battery; ami A and B are two 

 cwiract piecas of a pendulum interruptor. \ and B are iniiially 

 cf)-el; B is first broken; A i'i then broken, and the charL;e 

 reniininj in the condenser is measured by di<charging it throoyh 

 a yilvanoTieter, The Idne interval between the two ruptures 



■ II B^ 



M 



H3 



1 



:^=: E 





cin be varied one twenty-thousandth of a second at a tim?, and 

 ilie manner of di^cliargS of the conIen=er under the circum- 

 ■iiances is thus determined. Curi-es were olitained showing 

 (i) a merely leaking discharge ; (2) the critical discharge that 

 i lit fails to ever have negative vaUies ; (3) the critical discharge 

 that just fails to be oscillatory ; and (4) a thoroughly oscillatory 

 di<charge. 



The differential equation to be satisfied by the discharge is^ 



1 Q = o. 



ell Sj 



ivhere Q is the charge at any instant and p is the dissipation 

 coistaot. 



The solution of this for the case of oscillations is of the 

 fcrm — 



Q = Q„€-"" sec <()Cos. (// + <p). 



Experiment shows that the rate of damping is much greater 

 ihm that calculated from the aSove, assuming that the wire 

 circuit is the only seat of dissipation of energy. The explana- 

 li m offered is that dissipation also takes placi in the dielectric 

 of the condenser. In accordance with this it is possible to re- 

 pr )Juce the experimental curve by increasing the value ofp 

 from 28 ohms (the wire resistance in a particular case) to 59'4 

 o'.ims. The observed time period in this case is -009147 

 seconds ; the time period calculated on the above assumption is 

 009154 seconds. 



Kxperimental curves have also been obtained when iron rods 

 are inserted in the coil. Their chief characteristics are — 



(a) A decrease in time-period as the discharge progresses. 



($) Much more rapid decrement. 



That [B) is only very partially due to eddy currents in the iron, 

 was shown by repeating with a brass rod iiiserted in the place 

 • f iron. 



Experiments are also in progress in connection with circuits 

 of negligible capacity; a Wheatstone's bridge method being 

 etsployed. 



Sydney. 



Linnean Society of New South Wales, June 28. —The 

 following papers were read : — Notes on Australian Coleoptera, 

 with descriptions of new species, part xiii., by the Rev. T. 

 Blackburn. — Notes on the family Brachyscelidte, with descrip- 

 tions ol new species, part ii , by W. \V. Froggatt. This paper 

 deals with Si:hradei's two genera Opisthoscelis and Ascelis ; 

 the two original species of Schrader are re-described, and two 

 i.ew species of Ascelis are atided. — On the habit and use of 

 nardoo (ManiUa Drummoniiii, R.Br.), together with observa- 

 tions on the influence of water plants in retarding evaporation, 

 by T. L. B.ancrofl. The author has visited the south-western 

 corner of Queensland, journeying there viA South Australia and 

 eastward across Queensland. He first encountered nardno in 

 ijiiantity near Lake Copperamana on Cooper's Creek, where, 

 ' as over all' the drainage-areas of the Cooper, Diamantina, and 

 Georgina Rivers, the Blacks still make use of it as in the days 

 I of Burke and Wills. As originally stated, the plant thus 

 utilised under the name of nardoo is a Marsilea ; though doubt 

 has been cast upon the statement under the idea that it would 

 be impossible to obtain the involucres (sporocarps) in suHicient 

 quintity to serve as food ; and by those who took this view the 

 seeds of Seshania n't-nleala, I'ers. , were supposed to furnish the 

 nardoo of Burke and Wills. In a day one could gather about 

 a hundredweight of the dried rhizomes of the Marsilea with 

 Involucres attached, yielding perhaps about forty pounds weight 

 of the latter. It was found also that the nardoo did not grow 

 ia permanent water nor in swamps, but in country subject to 



NO. 1243 VOL. 48] 



inundaion ; and from specimens brought home vii;orous pot 

 plants were reared without difficulty. As regaids floating 

 water-plants retarding evaporation, the author has made ex- 

 periments with a series of gallon glass cells, some furnished with 

 [.eiiina, Azollii^ and Nymphcca gigaiitea, others without, and 

 with some of each placed out of doors in the sun, and others 

 in the shade and under cover, he found that evaporation was 

 neither retarded nor hastened by the presence of the aquatic 

 plants. 



Paris. 



Academy of Sciences, August 14 — M. Loewy in the chair. — 

 Oil the Tabulane, a truffle of the Caucasus, by M. A. Chatin. 

 This is a new variety of the Tirfezii Boiidieri, which is so 

 widely distributed in North Africaand Arabia. The roundness 

 of the spores resembles that of the African variety, whilst the 

 surface markings are those of Tirfezia Boiidieri Arahica. The 

 new variety, found about Tiflis and Baku, and sent from there 

 by the French Consul, M, Auzepi, has been named Tirfezia 

 Bouiheri Anzepii. The natives call it Tubulme. It is the size 

 of a large walnut, and its good cpiality and low price renders it 

 fit for European export.— Study of the microbian origin of 

 purulent surgical infection, by MM. S. Arloingand Ed. Chantre. 

 Purulent surgical infection has for its essential a.;ent the 

 orditt.ary microbes of suppuration (streptococci in the cases 

 examin-d). If microbes other than the preceding ones exist in 

 the woun Is, they complicate the purulent infection, but are not 

 nece>sary to its development. To produce purulent infection, the 

 streptococcus must assume the virulence which it possesses in the 

 acute and grave forms of puerperal septicemia, and not that 

 shown in ery.-ipelas. There is a suspicion of etiological rela- 

 tions between surgical purulent infection, puerperal septicemia, 

 and erysipelas, but it is not known as yet where and how the 

 transformation of the pathogenic properties of the strepto- 

 coccus take place which enables it to produce alternately these 

 diflerent clinical states. — ^On a product of incomplete oxidation 

 of aluminium, by M. Pionchon. Submitted to the action of an 

 oxy-hydrogen blow-pipe flame containing an excess of hydro- 

 gen, aluminium oxidises with vivid incandescence and is changed 

 into a substance of a greyish-black colour, in which the ratio 

 of ihe weight of oxygen to that of the aluminium has a value 

 approaching o 6, ami therefore very diff'erent from O'SSS, 

 the value characteristic of alumina. A treatuient of the sub- 

 stance with hydrochloric acid gave rise to a disengagement of 

 hydrogen and ihs formation ol aluminium chloride in solution, 

 besides leaving an insoluble re^idue. A quantitative estimation- 

 of these various constituents leads to the conclusion that the 

 grey .substance c mtains small quantities of freer aluminium and 

 alumina, and consists of a new oxide of aluminium, probably 

 represented by the formula AlgO^ = AljO, 2.VI„03, which may 

 be either a mixture or a compound. — On a new reaction of 

 eserine, and a green colouring matter derived from the 

 same alkaloid, by M. S. J. Fcrreira da Silva. — Synthetic pre- 

 paration of citric acid by ths fermentation of glucose, by M. 

 Charles Wchmer.— O.i the changes which have taken place in 

 the glacier of the Tee Rousse since the catastrophe of Saint- 

 Gervais, of 12th July, 1892, by MM. A. Delebecque and L. 

 Duparc. Nearly all the water from the glacier escapes at 

 present at the bottom, so that there is no immediate danger of 

 its accumulation. But this state of things is only temporary. 

 The valley of Monljoie appears to be exposed to a catastrophe 

 similar to that of 1892, which must happen sooner or la er. 

 No preventive measures seem possible. A diligent watch, 

 and an evacuation of the valley at the proper times seem to be 

 the sole remedies. 



Berlin. 



Physical Society, June 16.— Prof, von Helmhollz, Pre- 

 sident, in the chair. — Prof. Koenig gave an account of the 

 construction of tho newest forms of artificial larynx, more 

 especially the one described by Pro''. Julius Wollf. The capa- 

 bilities of the latter were demonstrated on a patient operated 

 upon by Prof. Wolfl', wh ) could not only speak continuously so as 

 to be audible throughout the whole lecture-room, but could also 

 sing. The president pointed out that this case fully substan- 

 tiated his theory as to the production of vowel-sounds, inasmuch 

 as the tones being initially produced by a vibrating elastic mem- 

 brane acquired their vowel quality solely by means of the vary- 

 ing shapes of the resonating buccal cavity. Prof. Fraenkel 

 exhibited a man who without either a natural or artificial larynx 

 could both speak and repeat the whole alphabet. It appeared 

 that the patient while speaking swallowed at frequent intervals 



