50 Prof, von Bezold's Researches on the Electrical Discharge. 



or negative be extracted, it will be understood that a positive 

 charge produces a positive figure when the electricity reaches 

 the point of the conductor before it reaches the coating — that 

 is, when D l is shorter than D 2 . If, on the other hand, the dis- 

 charge reaches the coating first, the conductor will be traversed 

 by the induced electricity in the opposite direction ; and hence 

 a negative figure must be formed upon the glass surface when 

 D 2 is shorter than D t . In the course of the motion this in- 

 duction discharge must meet, in the wire D v the electricity 

 coming direct from F, and thereby a compound character will 

 be imparted to the figure. 



Between these two arrangements with entirely opposite results 

 there must obviously be some in which no figures are formed, 

 as there is no reason why one should be formed in preference to 

 the other. This must be the case when the electricities from 

 both sides arrive simultaneously — that is, when D l and D 2 are 

 of the same length*. 



The experiments completely fulfilled these theoretical antici- 

 pations. With either kind of electricity, figures of both kinds 

 are obtained when the lengths of the wires are rightly chosen. 



To many a one who makes the experiment under not quite 

 favourable circumstances this statement may appear incorrect, 

 apart from the case in which, owing to perfect equality of the 

 two branches, no figures at all are formed ; for it may occur that 

 the whole of the figures seem at first sight positive, whatever be 

 the circumstances and whatever be the kind of electricity worked 

 with. 



The cause lies simply in the circumstance that the compound 

 negative figures belong in this case to that group which have 

 already a strongly positive character, and even, at first, can 

 scarcely be recognized as negative ; but the considerable dif- 

 ference in magnitude which occurs after a change of poles is 

 sufficient at once to remove any doubt as to the true nature of 

 the figures, and to prove the agreement of the experiments with 

 theoretical anticipations. 



To sum up, the following results were obtained : — 



1. When an electrical discharge, after traversing a spark-interval, 

 is offered two paths to the earth (a si tort one, and a long one in- 

 terrupted by a test-plate), with small striking -distances the discharge 

 is divided. With greater distances the electricity takes only the 

 shorter path, and even carries with it electricity of the same kind 

 from the other branch. 



2. If electrical waves be sent into a wire insulated at the end, 



* There may probably in this case be a small difference in favour of 

 the upper wire, since the electricity coming from below has to spread over 

 the entire coating. 



