72 Intelligence and Miscellaneous Articles. 



THE DISPLACEMENTS AND DEFORMATIONS OF ELECTRIC SPARKS 

 BY ELECTROSTATIC ACTIONS. BY AUG. RIGHI. 



Known experiments show that the electric discharge commences 

 when the electric density on the electrodes has attained a sufficient 

 value relatively to the dimensions of the balls, their quality, dis- 

 tance, &c* Supposing that the discharge is constituted by the 

 emission of electrified particles, it will commence at that one of the 

 two electrodes on which the density is the greater — from which we 

 derive the explanation of many phenomena. 



If, then, at but little distance from the place where the spark is 

 formed there are other electrified bodies, the particles will deviate 

 from their path, moving away from the bodies which have charges 

 of the same name as that of the electrode which repels them, and 

 approaching the bodies charged with the contrary electricity. 



Now the spark must pursue the path of the first particles re- 

 pelled ; for, by reason of the heat evolved, it offers less resist- 

 ance. Therefore the spark itself will deviate, as if it were a body 

 charged with electricity of the same sign as that of the electrode on 

 which the density previous to the discharge is the greater. 



The following is one of the ways in which I have verified this 

 class of facts : — The two stems bearing the discharge-balls are 

 arranged vertically one below the other, and at equal distance two 

 parallel vertical disks are kept constantly charged, the one with 

 positive, the other with negative electricity, by a Holtz machine 

 with auxiliary combs, the exciters of which are sufficiently distant 

 from one another for the sparks not to explode. It is readily ob- 

 served that, when the two disks are not charged, the form of the 

 spark produced between the two stems by the discharge of a con- 

 denser charged by another Holtz machine is nearly a straight line 

 (if the distance between the balls is not too great) ; but if the disks 

 are charged and if the two balls are not in all respects identical, 

 the spark is curved, approaching the one or the other disk. The 

 changes of shape are very remarkable when a liquid resistance such 

 that the spark becomes yellow is inserted in the discharge-circuit. 

 The spark then takes very curious forms ; and at the same time it 

 is observed to start from points of the electrodes situated laterally. 



Suppose, for example, that the two balls are identical in dimen- 

 sions and quality, but that one of them, the negative, communi- 

 cates with the earth ; the greater density is then on the positive 

 ball, and it is there that the discharge will commence. The spark, 

 in fact, is displaced aud deformed as a positively electrified flexible 

 body would be. The same effect is obtained if, both balls being 

 insulated, the diameter of the negative is greater than that of the 

 positive ball. — Comptes Rendus de V Academic des Sciences, Dec. 11, 

 1882, t. xcv. p. 1223-24. 



* A. Righi, " Sulle scariche elettriche," Nuovo Cimento, ser. 2 ; xvi. 

 pp. 89 & 97. 



