MEIDINGEH'S ELEMENTS. 



687 



which permit the passage of the wires between the balloon and the 

 rim of the cell. 



The current produced by Meidinger's elements is so feeble that 

 it cannot be used at all for experiments on heating effects, and is 

 insufficient for effecting chemical decompositions with rapidity. 

 The batteries are, however, very serviceable where a weak but very 

 constant current is required, as in electric telegraphy, and for similar 



FIG. 348 (A and C real size; B \ real size'). 



purposes, which will be described farther on. When the circuit is 

 uninterruptedly closed, such elements give a constant current for one 

 or two months ; if the circuit is only occasionally closed, as for elec- 

 tric bells etc., they will even act for a year or two. 



The balloon should never be placed upon the cell unless the latter 



