GALVANISM. 



battery having a smaller number, or 

 even into one corresponding in principle 

 to the simple battery with a single pair 

 of plates, such as the calorimotor. 

 These changes may be effected by alter- 

 ing the connexions of the plates, and 

 uniting several plates of the same metal 

 together, so that they may act as only 

 one plate ; or if the effect of a calorimotor 

 be desired, connecting all the zinc plates 

 together, and also all the copper plates, 

 so that the whole may act only as a 

 single pair. 



CHAPTER IV. 



Effects of Galvanism. 



(21.) THERE are three principal cir- 

 cumstances in which the electricity 

 produced by the voltaic battery differs 

 from that obtained from the ordinary 

 electrical machine; first, the very low 

 degree of intensity in which it exists in 

 the former, when compared with the 

 latter ; secondly, the very large quantity 

 of electricity which is set in motion by 

 the voltaic battery ; and thirdly, the 

 continuity of the current of voltaic elec- 

 tricity, and its perpetual reproduction, 

 even while this current is tending to 

 restore the equilibrium. The effects of 

 the voltaic pile have been compared by 

 the inventor of that instrument to those 

 of an electric battery of large dimen- 

 sions, but charged only to a low degree ; 

 in which case,'as appears from what has 

 already been said on this subject in the 

 Treatise on Electricity, a large quantity 

 of electricity may be contained, with a 

 very small tendency to escape, or, in 

 other words, with a very feeble in- 

 tensity. The comparison is, in many 

 respects, just ; but it fails in regard to 

 the third property we have noticed as 

 belonging to the voltaic apparatus ; 

 namely, the continuity of the current 

 arising from its perpetual reproduction 

 and circulation. 



However considerable may be the 

 power collected in a highly charged 

 electric battery, the whole of that power 

 is at once expended as soon as the cir- 

 cuit is completed. Its action may, while 

 it lasts, be sufficiently energetic ; but it 

 is exerted only for an instant ; and, like 

 the destructive operation of lightning, 

 can effect, during its momentary pas- 

 sage, only sudden and violent changes, 

 which it is beyond the power of the 

 experimentalist to regulate or control. 



On the contrary, the voltaic battery con- 

 tinues, for an indefinite time, to develop 

 and supply vast quantities of electricity, 

 which, far from being lost by returning 

 to their source, circulate in a perpetual 

 stream, and with undimished force. 

 The effects of this continued current on 

 the bodies subjected to its action, will, 

 therefore, be more definite, and will be 

 constantly accumulating; and their 

 amount will, in process of time, be in- 

 comparably greater than even those of 

 the ordinary electrical explosion. We 

 shall accordingly find that changes in 

 the composition of bodies are effected 

 by galvanism which can be accom- 

 plished by no other means. Hence 

 may be conceived the advantages which 

 have accrued to science from the ac- 

 quisition of an instrument of such vast 

 power, and admitting of such extensive 

 application in the wide field of chemical 

 research. 



It will be convenient to study the 

 effects of galvanism in their relation to 

 the three circumstances which have 

 been noticed as characterizing its ope- 

 ration when contrasted with those of 

 ordinary electricity. 



1. Ordinary Electrical effects re- 

 sulting from Galvanism. 



(22.) The degree of intensity in which 

 the electricity developed by a single 

 galvanic circle exists, is so extremely 

 low, that its action produces none of 

 the usual phenomena exhibited by the 

 common electrical machine. Even from 

 the largest calorimotor that has yet 

 been constructed, it is not possible to 

 obtain indications of electrical attraction 

 and repulsion, such as are given by the 

 feeblest degree of excitation to a piece 

 of sealing-wax. With a few alternations 

 of plates and interposed fluid, as in the 

 pile or trough battery, electrical indica- 

 tions may be obtained, by means of .an 

 ordinary condenser. It is necessary in 

 these experiments to advert to the dis- 

 tinction already pointed out ( 15.) be- 

 tween single and compound circles as 

 to the denomination of the extremities 

 or poles of the battery. In the com- 

 pound circles the zinc side is found, to 

 be positive and the copper negative. 

 When fifty pairs of plates are employed, 

 a delicate gold-leaf electrometer will be 

 affected, without the aid of the condenser, 

 and with a series of one thousand 

 groups, even pith balls are made to 

 diverge. In order to exhibit these ef. 



