928 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



diminishes their conductivity, making it necessary, at intervals of 

 fifteen or twenty clays, to renew the battery and submit the car- 

 bons to thorough cleansing, l)y immersion in water for twenty- 

 four hours or more.. The bichromate solution has to be renewed 

 every day for main circuits, and for locals, twice a day. This 

 battery is properly called chromic acid battery, in contradistinc- 

 tion to the nitric acid batteries of Grove and Bunsen. Chromic 

 acid is the active ingredient in the porous cup. The greater 

 attraction of the sulphuric acid takes the potassa, and the chromic 

 acid is set free, but the quantity is so limited (not more than one 

 twcntj^-fifth part of its %veight) that the battery can never be but 

 short-lived and inconsistant. 



The facility with which chromic acid parts with oxygen to form 

 water with the hydrogen, which would otherwise appear in a free 

 state at the negative plate, is such as to make this battery very 

 powerful while it lasts, in both quantity and intensity. When we 

 form connection by contract with a short ground wire, a brilliant 

 flame of fire is elicited, which has Ijeen referred to, by respectable 

 electricians, as a property highly meritorious. It is a valuable 

 indication in a battery for electrolytic purposes, but in telegraphy 

 it is the reverse. It indicates a kind of force, not only liable, 

 under certain circumstances, to heat and destroy the magnet, but 

 prone to escape at every possible opportunity. Everv particle of 

 aqueous vapor that touches the telegraph wire, receives and car- 

 ries off a full cliarge, and every cobweb, or other fibrous material 

 that may chance to hang across the wire in a damp atmosphere, 

 carries oft* a stream of the galvanic force. On the whole, it seems 

 like a hard choice of evils to take this in place of Grove's batterj-; 

 indeed, the objections to both are serious, and call loudly for some- 

 thing better. 



In my numerous testings with both the chromic acid and nitric 

 acid batteries, I have always been annoyed with irregularities in 

 their action. I have set for hours to observe the perturbations of 

 the needle under their action. When using the quantity galvano- 

 meter, I have observed the needle to vibrate, sometimes gently and 

 steadily, and at others abruptly, to the distance of 4° or 5^, and have 

 seen it moving back and forth over an arc of 10° or 12° in the 

 course of an hour. These vibrations are not so large when I 

 use the intensity galvanometer. 



Daniels' sulphate of copjjer battery has always been emphati- 

 cally pronounced " the constant battery," but it is not entirely 

 constant, nor free from other objections. 



