GALVANISM. 371 



of disks composing these, their power is diminished. Their effects have been 

 generally limited to those produced on the condenser; but, by diminishing con- 

 siderably the number of disks, M. Pelletier has succeeded in decomposing 

 water by these instruments. Their action, however, ceases after the lapse of 

 a certain period, when the paper has lost all its humidity. 



The sources of the disengagement of electricity in this pile are various and 

 complicated. Besides what may arise from the contact of heterogeneous sub- 

 stances, chemical action intervenes in several ways. The organic matter acts 

 upon the zinc as well as upon the peroxide of manganese, reducing the latter 

 to a lower state of oxydation. 



Zamboni examined the effects produced on the electricity of the pile by 

 soaking the paper to which the tin leaf was pasted in different liquids, and 

 found that, according as the state of the other side of the paper was changed, 

 the poles of the pile were thrown to different ends. If the paper be soaked 

 in oil, the poles are in a direction contrary to that which they assume when a 

 coating of manganese is used. On the other hand, when the paper is soaked 

 in honey, in an alkaline solution, a solution of the sulphate of zinc, or half 

 curdled milk, the poles have the same position as when they arc coated with 

 manganese. 



No sensible shock is received from a pile of two thousand pairs, although 

 the tension at the poles is sufficient to produce a sensible effect on the proof 

 plane, and a condenser applied to one of the poles will, in a few moments, give 

 sparks an inch in length, and a Leyden battery may receive from it a charge. 



The conducting power of the vapor suspended in the atmosphere, carrying 

 away a portion of the electricity of these piles from their poles, produces a con- 

 ( tinual variation in the tension of the electricity at these points. 



Zamboni found that the energy of the pile was greater in summer than in 

 winter, whether measured by the tension of the electricity at the poles, or the 

 rate at which the fluids were produced and propagated. M. Doune compared 

 the tension with the height of the barometer, but could discover no relation be- 

 tween them. He found the tension the same in a vacuum as under the pressure 

 of the atmosphere. 



It is known that electricity may be developed on a plate of a single metal, 

 by causing one surface of the plate to be acted on chemically, in a degree or 

 manner different from the other surface. This may be effected by merely render- 

 ing one surface smooth and the other rough. This expedient is said to have been 

 resorted to in the construction of a Voltaic battery with one metal, without any 

 liquid element. From sixty to eighty plates of zinc, of four square inches of 

 surface, are made clean and polished on one side, the other remaining rough as 

 it comes from the mould. These are fixed in a wooden trough parallel to each 

 other, their polished surfaces all turned toward the same end of the trough, and ? 

 with an open space between the successive plates of from the tenth to the | 

 twentieth part of an inch. These intermediate spaces are filled by thin plates < 

 of atmospheric air. If one extremity of this apparatus be put in communica- J 

 tion with the ground, and the other with an electroscope, the latter will receive ( 

 a very sensible charge. 



We can regard the dry pile in no other light than as an extended \ oltaic ( 

 series. The moisture, which is essential to its activity, is in the condition of ( 

 anything but freedom of motion ; so that the renewal of contact by the pres- 

 ence of fresh particles, which seems essential in all developments of electrici- 

 ty, exists in the lowest degree ; and then again the feeble chemical actions ex- 

 isting between elements under circumstances so unfavorable, all conspire in 

 producing the small quantity of electricity for which these instruments are re- 

 ) markable ; while the great length of series produces the high tension of the ( 



