372 



GALVANISM. 



poles. It is only recently that chemical decomposition has been obtained by 

 the dry pile. Mr. Gassiot prepaired 10,000 Zamboni's disks ; and by carefully 

 directing the electricity through hydriodate of potassium on a slip of glass, he 

 obtained the development of iodine on the wire connected with the oxide of 

 manganese end of the series. He could not obtain heating effects on Harris's 

 thermo-electroscope, unless he allowed the charge to pass in sparks. 



The only uses to which dry piles have been hitherto applied are 1. To 

 produce a continued motion, by an electrical pendulum suspended between the 

 contrary poles of two such piles placed side by side, so that the positive pole 

 of one and the negative pole of the other shall be at the summit. This motion 

 will be continued as long as sufficient moisture is retained by the elements of 

 the piles to sustain their activity ; but it will not be regular, since the develop- 

 ment of electricity will be affected by variable atmospheric causes. 2. In con- 

 densing electrometers, to detect the presence of very small quantities of elec- 

 tricity on the inferior plate of the condenser.* 



I shall conclude this notice of the progressive advancement of Voltaic elec- 

 tricity here. The phenomena and laws whose development followed the ex- 

 perimental researches which have been explained, will probably be noticed on a 

 future occasion, when I shall offer a view of the actual state of Voltaic elec- 

 tricity, its relations with magnetism and heat. 



* Becquerel, TraitS de 1'Electricitg. torn, i., p. 166. 



I 



