RECENT PROGRESS IN PUYSICS. 383 



one end, by the attracted electricity, and those at the otlier end, by the 

 repelled, if the conductor was touched tlie distant pair of sus[)ended 

 balls ollapsed, while the diverjijence of" those nearest m, increased. 



Although tliis experiment, if proper piecaution be taken, such as 

 not charging m too strongly, does not easily fail, yet it has not suc- 

 ceeded ibr many observers, and to this may be attributed the whole 

 controversy on the nature of disguised electricity. The doubt about 

 the experiment arises, as liiess has properly remarked, from the fact 

 that the electricity of the inducing body acts at right angles to the 

 electroscopic pendulums, which it causes to deviate from their perpen- 

 dicular position. 



liicss has remedied this defect by the following arrangement. A 

 metallic rod about 5 inches long and 3 lines thick, with rounded ends, 

 is fastened by the middle to an insulating handle, as shown in fig. 22^ 

 and by means of this handle is held in a vertical po- 

 sition. It is provided at both ends with a pith ball ^'?" ^^• 

 suspended by a linen thread. 



M 



If an electrified body be brought near the lower end 

 both balls will be repelled. Suppose the approaching 

 body is ])ositively electrified, then the upper pendu- 

 lum is deflected with -|- E, the under one with — E , / 

 as may be tested by presenting a rubbed glass or wv 

 stick of sealing wax. 



If the metallic rod be now touched, the upper pendulum falls, while 

 the divergence of the under one is increased. 



At the lower end of the rod, and in the ball there, only disguised 

 — E is now femnd ; the electricity of this end, though it is disguised, 

 repels the like-named electricity of the ball ; hence disguised elec- 

 tricity acts as freely at a distance as though it were not disguised. 



The divergence of the lower pendulum proves, that the particles of 

 disguised electricity repel each other precisely in the same manner as 

 though they were not disguised, consequently its propagating power 

 is similar to that of free electricity ; and if (iisguised electricity can- 

 not be carried off to the ground by conductors, the cause is not that 

 it has not propagating power, but that it is restrained by the attrac- 

 tion of the opposite electricity of the inducing and restraming body. 

 To deny to disguised electricity its ordinary properties, is like assert- 

 ing, that because a stone lies upon the ground it has lost its gravity. 



The experiment of Eie.ss has proved, beyond all contradiction, that 

 latent electricity acts at a distance as perfectly as ^'g- ^3. 



though it were not latent. If an electrified body (a, * ^ 



Fig. 23) has rendered latent the opposite electricity fa^ (^6^\ 

 on a conductor connected with the earth, any point K.^^ ^v^-^ 

 (c) in the vicinity is acted on by the electricity of a 

 as well as by that of b; but since a and b are charged with oppo- 

 site kinds of electricity, only the difference of their effect can be 

 observed in c. 



After this contested question might have been considered as settled 

 by the experiment of liiess, Knochenhauer brought forward new ob- 

 jecfions. (Fogg. Ann., XLVII, 444.) 



