50 



LOCALIZED ELECTRIZATION. 



practice its employment has been attended with inconveniences 

 that have prevented its general adoption ; although it rendered 

 valuable service in the first researches into electro-magnetism. 



B, — Batteries of large surface and ivith constant currents. 



(a), DanielVs hattery (fig. 9). In 1836, Daniell contrived a 

 battery in which he succeeded in avoiding rapid weakening of the 



action, or variations 

 of the power during 

 the passage of the cur- 

 rent. It is a battery 

 with porous organic 

 diaphragms, and with 

 two liquids, a solution 

 of sulphate of copper 

 for the copper, and 

 acidulated or saline 

 water for the zinc. 

 It is highly useful 

 for protracted experi- 

 ments, and especially 

 for inquiries into the 

 chemical effects of 

 the current. 

 (6). Groves constant lattery (fig. 10) resembles that of Daniell in 

 having two kinds of liquid and a diaphragui ; but the copper is 

 replaced by platinum, the sulphate of copper 

 by nitric acid, and the porous diaphragm 

 is of smooth unglazed porcelain. This bat- 

 tery is the most useful for the production 

 of the electric current ; because it combines 

 enormous power with a constancy only little 

 less than that of Daniell. 



(c). Bunsens constant hattery (fig. 11) is 

 a modification of that of Grove by the sub- 

 stitution of carbon for the platinum. It is 

 constant for a longer period, but is less 

 energetic than that of Grove. It is much 

 in use, especially in Germany. 



The batteries of Bonijol and of Deleuil 

 differ from that of Bunsen only in the form and place given to 

 the carbon. 



Among all the foregoing batteries, that of Daniell has been 

 most generally employed for medical purposes. 



Fig. 9.— Darnell's battery. 



Fig. 10.— Grove's battery. 



