278 SEC. 10. ELECTRICITY. 



and a cylindrical tube, each of which holds one of the two equally long wires 

 as electrodes. The tension of electricity with which passage occurs is much 

 greater when the wire serves as cathode in the narrow part than when it is 

 anode. This may be shown if a spark micrometer be introduced in the induc- 

 tion current near the tube, and for each of the two directions the interval of 

 the balls be determined with which the current takes the path through the 

 tube. If the wire in the wide reservoir, being cathode, be placed in conductive 

 connexion with the third aluminium wire, which is in the beginning of the 

 cylindrical tube, the current can no longer pass over in the latter to the former. 

 This, therefore, loses its negative light, and only with the greater tension, 

 such as occurs with the other direction, is the passage of electricity effected. 

 (Of. Pogg. Ann., Bd. 136, p. 197.) 



The aluminium wire, which is quite sheathed with glass, with exception 

 of the last cross section, is taken as cathode of the opening induction- current. 

 The straight discharge from the cross section, when the tubes are brought 

 over and between the poles of an electro-magnet, behaves like a flexible con- 

 ductor which is fixed at one end and at the other freely movable, and follows 

 the Laplace-Birl laws. (Cf. Pogg. Ann., B. 136, p. 213.) 



1377e. Three Tubes of Glass, with rarefied air to show the 

 magnetic behaviour of the negative glow light. 



Prof. Jfittorf, Miinster. 



5. The negative electric discharge which, with great rarefaction, occurs at 

 a cathode with small surface, raises the conducting particles of gas to a very 

 high temperature. When strong induction currents are used, these, notwith- 

 standing their small mass, are capable of raising the surface of badly-conducting 

 solid bodies with which they come into contact to a red heat. This heating, 

 which the negative discharge gives in much greater degree than the positive, 

 produces with the best light-givers, like sulphide of calcium, a light of dazzling 

 intensity. 



1377f. Three Glass Tubes of Rarefied Air and Sulphide 



of Calcium, to show the phosphorescence of the negative electric 

 light. Prof. Hittorf, Munster. 



1378. Gassiot's Star. Frederick Guthrie, F.R.S. 



This exhibits (1) the varieties of the electric discharge through various 

 rarefied gases in tubes of different shapes, and (2) by being rotated shows by 

 the retention of images the intermittent nature of the discharge. 



1379. Block Specimen of Glass, 2 inches high, penetrated 

 vertically by an electric discharge. (By Ruhmkorff, of Paris.) 



George Gore, F.R.S. 



1380. Effect of Lightning. Portion of a half-sovereign and 

 a fragment of sheet iron fused together by a discharge of lightning 

 in the colony of Natal. This and other coins were in a tin box, 

 of which this fragment alone remained. 



Robert James Mann, M.D. 



1381. Metals fused into Glass by Lightning. 



Alfred B. Harding. 



!Frame No. 1 consists of strips of zinc, tin, and lead, fused into glass by an 

 actual flash of lightning, collected by means of " exploring wires " stretched 



