and its Effects. 11 



current, for under all circumstances these sparks are smaller with 

 a long thin induction wire than with a short thick one. 



What has here been said of sparks in free air, is partially true 

 also for the pha;nomena of light in a partial vacuum. Under 

 otherwise equal circumstances they are not so fully developed 

 with small, as with large condensers. 



Nevertheless it must be here remarked, that in general the 

 strengthening action of condensers is les,s prominent the more 

 intense the induction current itself, and the more perfect or 

 conducting the vacuum. When the current in the induction 

 wire was excited by two of Grove's elements, and the receiver 

 exhausted to a few lines of mercury pressure, the great condenser 

 itself scarcely exerted any influence upon the light produced; 

 on the other hand, however, this influence immediately mani- 

 fested itself when a little air was introduced, or when the long 

 thin induction wire was replaced by the short thick one. 



In all condensers, the wires which connected the same with 

 the hammer were always at a short distance from, and on oppo- 

 site sides of, the point of interruption. They can be connected 

 with other and more distant points of the circuit, but by so doing 

 their action is weaker. 



Voltaic Battery. 



On this subject I have only to remark, that, owing to the 

 small dimensions of my apparatus, I never found it necessary to 

 use more than two of Grove's elements, all the phajnomcna which 

 I wished to study being sufficiently developed with that number. 



Additional Apparatus. 



Amongst these may be mentioned the small instrument, which 

 I will call a discharger. It is requisite in order to observe many 

 of the phaenomena of the induction apparatus with convenience 

 and without being exposed to electric shocks. On the whole, 

 my discharger has somewhat the form of a spark micrometer, 

 but its use is more general ; the platinum wires, carried by glass 

 rods and connected with the poles of the induction coil, are, in 

 the horizontal position, capable of a horizontal, vertical, and 

 rotatory motion ; and, in the vertical position, they can be placed 

 side by side, or one above another. These wires, on whose ex- 

 tremities thinner wires, knobs, or discs can be fastened, serve 

 also, when in a vertical position, as electrodes in the chemical 

 decompositions which can be eficctcd by means of the induction 

 current. 



The second apparatus of this kind is known as the electric 

 egg, whose construction needs no description. 



