502 SCIENTIFIC RECORD FOR 1882, 



tween the curvature of the electrodes is greater and the potential itself 

 higher ; (3) for a given length of spark, taken between electrodes of 

 equal curvature, the potential varies with the diameter of the sphere, 

 so that a sphere can be found of such diameter that the potential shall 

 be a maximum ; (4) the diameter of these equal spheres corresponding 

 to the maximum is as much smaller as the potential is itself smaller. 

 These two values increase together, but not proportionally ; (5) the 

 potentials V corresponding to the explosive distances d between two 

 planes can be expressed by the empirical hyperbola V^ = 10500 {8 + 

 0.08) S. {J. Phys., April, II, i, p. 169 ; Ann. Chim. Phys., April, Y, xxv, 

 p. 486.) 



Keitlinger and VVachter explain the Lichtenberg figures by a disag- ' 

 gregation of the electrodes by the passage of positive electricity. Those 

 positive figures which are radiating in form, are attributed to the trans- 

 portation electrically of particles of dust torn from the positive elec- 

 trode ; while those positive and negative figures alike, which have rounded 

 contours, are attributed to the transport of the dust by the gases shaken 

 by the discharge. {J. Phyft., April, II, i, p. 203.) 



Goldstein has investigated the question of the influence of the shape 

 of the kathode on the distribution of the phosphorescent light in Geiss- 

 ler's tubes, and figures some remarkable forms obtained. {Phil. Mag., 

 December, V, xiv, p. 455.) 



Spottiswoode, in a lecture at the Eoyal Institution upon matter and 

 magneto-electric action, gave a resumS of the work accomplished by 

 himself and Moulton in studying the electric discharge in rarefied gases, 

 especially with the use of alternating currents. {Nature, April, xxv, 

 p. 539.) 



Jacquelain has presented a memoir to the French Academy on the 

 purification of graphitoidal carbons, either natural or artificial, with 

 special reference to the electric light. He concludes that the luminous 

 power and the steadiness of the voltaic arc from a pure carbon, obtained 

 either directly or by a method of purification, increase with the den- 

 sity, the hardness, and the purity. The natural graphitoidal carbon 

 from Siberia has the unexpected property of giving when purified double 

 the light of the unpurified material. Its light-giving power surpasses 

 by one-sixth that of the purest artificial carbon, although a very hard 

 and brilliant pure artificial carbon has given an illumination equal to 

 236 carcels. Though the hardness of gas carbon is greater, its density 

 is less than that of the Siberian graphite, the former ranging from 1.90 

 to 1.99, while that of the latter is from 2.28 to 2.41. To this its superior 

 light-giving power is ascribed. {Ann. Chim. Phys., December, V, xxviii, 

 p. 537.) 



Foussereau has published an article on electric lighting, in which the 

 subject is divided as follows : 1st. Preparation of the carbons. The car- 

 bons most in use in France are those of Carre, made of coke, calcined 

 lampblack, and thick gum- water; of Gauduiu, made of the coke fix)m 



