V. DISCHARGE. 323 



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

 magnetic behaviour of the negative light. 



Prof. Hittorf, Munster. 



The aluminium wire, which is quite sheathed with glass, with the excep- 

 tion of the end, 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 conductor 

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

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



1377f. Three Glass Tubes of Rarefied Air and Sulphide 

 of Calcium^ to show the phosphorescence of the negative electric 

 light. Prof. Hittorf, Munster. 



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. 



1378. Gassiot's Star. Frederick Guthrie. 



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 Ruhmkorffj 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 after the passage of the 

 discharge. 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 

 over the grounds of the late Andrew Crosse, and conveyed into his electrical 

 room, as shown in the stereograph. It was here accumulated in the great 

 Leyden battery of 50 jars, and passed thence by dischargers through the 

 metals, which were burnt into the glass on which the strips were laid. 



Frame No. 2 contains composite strips of copper and iron, gold and tin, 

 and gold, silver, and copper, fused in like manner. 



A photograph of the Leyden battery, with which the experiments were per- 

 formed, accompanies the frames. 



1382. " Thunder House,** or model to illustrate the identity 

 of lightning and electricity, and the use of lightning conductors 



X 2 



