

I'1IY>KX I'l. OF, l\ 



connection between the elect ric ami in.> 



a Maxwell's equal i due to tl. 



that they are not dn ITOMIOM in tin- ether, 



but concomitants or remits of tin- disturbance, 

 just as the eondniv. 1 rarefactions of t In- 



air that affect the ear drum are concomita: 

 the displacements of the air. 



Sowre*. Trowbrtdgc ("American Journal of 



-e, w September), br examining tin- char. 

 istic flame of the discharge of a large n mm 

 Plant*'- ct-lls tlnd* that it is oscillatory, ami he con- 

 clude* that a eHl may U> regarded as a Iraky con- 

 denser, and that it- litharge is always essentially 



hrift 



fQr 1 lie," Feb. 20) have investigated tin- 



Jacques carU.n cell ," Annual rvelopa-d ,. L8M, 

 page 648) and fl n<l that a coll of carbon and iron dill- 

 ping into fu*ed rat. -h has at lir-i I 

 small lie- ."live force, which riSM 

 nly. when tin- ir>n a m >ndi- 

 ut one volt. Tin- current i- very incon- 

 .ii). 1 I In- ir.-n is rapidly jH.lari/.ed. although 

 tin- can In- miu-dicd t<> -ome extent by passing a 

 m of air through tin- fu--d Hect n.l'yte. 



Conduction. Muller (WledeflUUin'l "" Annal-n." 

 January) has made a new measurement of the con- 

 ductivity of air. taking into account the residual 

 mercury vajnir and the specific heat of the glass 

 employed and investigating all source- of . 

 His re'-ult is 0-000056 in C.<J.S. units. Price (Lon- 

 don Physical Society) luis invest igated the proper- 

 ties of a proposed form of submarine cable made of 

 itric conductors interrupted alternately 

 at different points throughout its length. He finds 

 tie-ally that the speed of such a cable can not 

 exceed that of the ordinary type, but it appears 

 from exjH-rimcnt that the definition of signals is 

 better, and that the clearness ( ,f definition increases 

 within certain limits, the greater the nunil 

 Mibdi visions. Baly (London Physical Society. .Ian. 



M the theory that conduction in gV 

 lytic. bringing "up against it the following 

 facts : (1) The sign of the change on the supposed 

 gaseous ion is variable; (2) a gas has initial re- 

 sistance; (3) Ohm's law does not hold ; i-li the -up- 

 posed gaseous electrolyte is permanent : 

 mixture of gases must also be an electrolyte : at 

 the potential gradient in a vacuum tubi-. when the 

 current passes, is uneven. Criticism of the au- 

 thor's views was distinctly unfavorable (see " Na- 

 ture," Jan. 28). 



Resistance (see also above). Trowbridge ("Pro- 

 ceedings of the American Academy," April) finds 

 that Ohm's law does not hold good for electrical 

 discharges in air and rarefied gases. A 6-inch dis- 

 charge encounters no more resistance than one only 

 2 inches long, and probably the resistance met bv a 

 flash of lightning a mile long is no greater. The 

 author believes that electrical ox illations are of 

 the nature of voltaic arcs and that the discharges 

 in Crookes tubes are arcs, and he is " forced to the 

 conclusion that under high electrical stress the 

 ether breaks down and becomes a good conductor." 

 *-m ("Philosophical Magazii. :t>er) 



examines the relation betw,.n the electric resist- 

 ance of a metallic wire and itl t.-mperaturc. with a 

 Tiew to recu latin if the plntumm thermometer, and 

 deduces the formula (U + a) * = p (t + b). where 

 a, p, and 6 are constant H. Thi- h. mop- 



representative of fact than previous formulas and 

 as simple as any. Swyngedau ademy of 



- VCS, March is sp., r k resistance as'de- 



pending on length, sect ion. and tomi* rature. and 

 on the nature of the luminous conductor that 

 stitutes the spark. The consequences of thi- view- 

 differ from those of Thonw.n, who regaitls the re- 

 sistance as constant, and lead to the result that a 



iiarp* that is . when the 



capacity is lar-c In-come- c,.nt inu-u- \\'li.-n ti 

 pa.itv is small noii-h. l'o^i (" Nu >\o Cimento." 

 VoL 1 ^ > fnuls t hat in >alt -olut ion- win-re \ lu- 

 ff clecin.:\ produce - i.-eiitralion 

 at the p<.-itive pnh-. the increases \\ hen 

 the li.|iiid moves opposite to the current and d. 

 Creases when it m-. \.-wiih the current, the in- 

 crease in the first case being greater than the 

 decrease in the second. Wliere the concentration i- 

 greater at the negative poleihr,! 1 <-rscd, 

 and when then- i- no dilTn. : 



the resi-talice is unalTected by the l;i..li..|| of the 



liijuiil. Kr-kine (Wiedemanni "Annalen. 



vemin-r) finds that the elect ric reaistanoe of a: 



trolyte for rapid oscillation- i- directly pi 

 tional to the thickness reipiired to produce a . 

 amount of damping. 



\ViedelllHl!' 



nalen," l-'ebruar\ i finds that a thin win-, elect rically 

 harp-d. IOM-S it- chart:' 1 more n-adily in air whei'i 



hot than cold. The diiTen-nce between a pot 



and a negative -har.L r e is al-o more marked at hi^'li 

 tt-mperalnres. the latter bein-r n , ( , r e rapidlv 

 iMited. \Ve-einl. inek iNViedemaiin's Aniialen." 

 February) finds that the quantity of negative elec- 

 tricity CUBOharged from a point into hydros 

 greater than the quantity of po-itive elect ricity di 

 charged ;it t he -ame p. .fent ial : but t he init ia'l dis- 

 cliar-e p. .tent ial- an- IK-I nece--arily different. 



Tin >/<"//. i-ee also ui. above). 



Schuster (I'.riti-h As-ociatioii) has niea-ured the 

 yeloc-ity with which metallic particles are pro- 

 jected from the Hern-odes in a <\mrk discharge, as 

 mined by the -pert ro-cope. lie photographed 

 the -park sjM-("-trum on a film fixed to the rim of a 

 rapidly revolving wheel and moving with a linear 

 speed of 80 metres a second at rifful angles to tin- 

 spectroM-ope .-lit. The metallic In ar in- 



clined on account of the finite velocity of the lumi- 

 iions molecule-, while the air line- remain -trai^lit. 

 \\'ith two xinc j>oles the velocity was found gradu- 

 ally to diminish from 2,000 metres per second to 400 

 a- the distance from the pole increased. With one 

 zinc and one bismuth pole the bismuth in 

 cases had a smaller speed. Warburg (\\ 

 mann's " Annalen." November) has -tudied what he 

 calls the "retardation" the period clap-in:: be- 

 tween the establishment of the necessary difference 

 of {potential and the con-.-pondinu r discharp-. It 

 varies from a few minutes to a fraction of a second 

 and is due to a noiiluminous partial di-H. 



md fisrillafitiH. I'.o-c il'.riti-h 

 As-ociati(n) has succeeded ill obtaining el< 

 waves -ix millimetres in length. In a lecture at the 

 I n-t it ut ion he has >h..wn that numcrcii- i \ -- 



tais polarise the waves, Prude <\Viedem;inn'- ,\n- 



nalen." Janunrv) finds that eledri.- n not 



totally reflected by a bridge laid acp.-- a wire 8VS- 

 teni. Itut undergo a di-placement of phase ami a 

 diminution of amplitude, depending .n the ratio of 

 the length of the bridge to that of the 

 noting the number of nodes alon^ the wire the ab- 

 sorptive power for electric waves may be mea-un-d. 

 :to ( Atti .lei Lincei." VI. pace 4) find- that 

 the principal indices of refraction of electric waves 

 in wood- are proportional to the square root of the 

 dielectric constant in the -ame direct ion- a- M;i\- 

 wHl's theory requires. PocklingtOfl (Cambridge 

 Philosophical S<.ri.- lin.ls by mathemat- 



ical treatment that wit h accurate t lining the mag- 

 nitude of an induced current is independent of 

 the thickness of the wire, and that the thinner the 

 wire the more sensitive it i- to accuracy of tuning. 

 In the ca.e of a helical wire, when the reciprocal 

 of its radius can be neglected, there are two po~- i- 

 ble velocities of propagation, one measured along 



