652 CONDENSATION OF GALVANIC ELECTRICITY., 



two metals. For if electricity is withdrawn from the 

 metals, so as for a moment to diminish the tension, the 

 electromotive force instantly reproduces whatever ten- 

 sion of electricity it is capable' of producing. In fact 

 a second is more than sufficient -to charge the condenser 

 as strongly as it is possible to charge it under the cir- 

 cumstances of the experiment. 



The condenser being thus charged, the pieces of 

 copper and zinc are placed aside, and the upper plate 

 of the condenser is lifted straight up by its insu- 

 lating handle and brought in contact with the knob 

 of the electroscope ; a divergence of the gold leaves 

 takes place, for the two electricities which were con- 

 densed and bound in the apparatus are set free by 

 the lifting of the upper plate, and the free electricity of 

 the latter is communicated to the electroscope. The 

 quantity of free eleptricity, in spite of the condensation 

 which took place, is nevertheless so small that it causes 

 a divergence of only a few millimetres. If, as has been 

 assumed in the figure, the upper plate of the condenser 

 has been charged by the copper plate, it communicates 

 a positive charge to the electroscope. This may be 

 proved by bringing a rubbed glass rod near the elec- 

 troscope; it increases the divergence of the leaves. 

 An examination by the electroscope of the lower plate 

 of the condenser, which was in contact with the zinc, 

 shows it to be charged with negative electricity. 



It requires considerable care to exhibit the galvanic electricity in 

 these experiments, on account of the smalhiess of the quantities of 

 electricity generated. The insulation should everywhere be perfect, 

 and must be examined before the experiments. See that no liquid 

 from the paper has dropped upon the metal strips close to the con- 

 denser, or upon the sealing-wax handles. The insulating surfaces 



