into the Cause of Voltaic Electricity. 289 



requires a much stronger tension ; but the difference between 

 the tension in the two cases increases in proportion as the 

 liquid with which the pile is charged is a better conductor ; 

 such should be the fact, for when the liquid is a good con- 

 ductor the two electricities can reunite with greater facility 

 through the pile, if one of them be not furnished with means 

 of flowing into the earth. Numerous experiments have been 

 made in relation to this circumstance by charging the same 

 pile in succession with river water (Rhone water), a solution 

 of sulphate of soda, and a diluted solution of nitric acid. I 

 have observed, in particular, that to obtain the maximum ten- 

 sion the pole where the tension is perceived must be left in 

 contact with the condenser for a considerable time, if the li- 

 quid with which the pile is charged be simply water ; rather 

 a shorter, though still an appreciable time, if it be sulphate 

 of soda ; and, lastly, an almost insensible period if it be the 

 solution of nitric acid. The following are the results of an 

 experiment performed with a pile of ten elements, zinc and 

 copper, the surfaces four inches square, charged with river 

 water : 



Duration of contact of the pole with the condenser, 



15" 



30" 



60". 

 Divergence of the gold leaves of the electroscope, 



2° 



6° 



(The gold leaves touch the envelope of the electroscope). 



If we wish to charge the condenser twice in succession with 

 the same pile, a period of time must be allowed to elapse be- 

 tween the two charges, varying according to the nature of the 

 liquid with which the pile is charged, exactly in the same 

 manner as the duration of the contact of the condenser and the 

 pole varies. These results may easily be explained by consi- 

 dering, that as river water has much less action upon zinc, a 

 much longer time is required for the development of a certain 

 quantity of electricity, while with saline and especially with 

 acid solutions, this electricity is developed instantaneously. 

 That in the first case, notwithstanding its slow production, 

 there may still be a considerable quantity of electricity accumu- 

 lated at the poles, is a fact which arises from the imperfect 

 conductibility of the pile. I have seen a pile of 120 elements, 

 zinc and copper, charged only with pure water, give sparks at 

 both its poles, in very dry weather in winter, like an electrical 

 machine, while the same pile, charged with an acid solution, 



Third Series. Vol. 1 1. No. 67. Sept 1837. 2 P 



