Contact Theory of Galvanism. 375 



happens at times that current equilibrium is obtained very ex- 

 actly, and then this equilibrium continues even when any 

 quantity of muriatic acid is added to the fluid contained in 

 one of the systems; the one system may even be filled much 

 higher with dilute acid than that producing the opposite cur- 

 rent is with water. It is true that an ascendency of the one 

 current is gradually developed, undoubtedly in consequence of 

 the changing action of the muriatic acid upon the plates, hut 

 it is not the cells with acid, in which a tumultuous development 

 of gas takes place, but the water-cells which obtain this ascend- 

 ency. If on the other hand each half of the cells is con- 

 nected by itself by the multiplier, that instrument experiences 

 from the acid cells a very stormy action, from the water-cells 

 a weak action merely. How then the result of this experi- 

 ment is to be explained accoi'ding to the chemical theory, 

 I cannot conceive. According to the theory of contact the 

 explanation is easy. For according to this the addition of 

 muriatic acid increases the action only by diminishing the 

 opposition to the conduction present in the circuit, and this 

 diminution is of as great advantage to the electricity (which is 

 developed by contact in the ceils without acid,) in its entire 

 circulation through the circuit, as the electricity of the pairs 

 of plates which are in the very acid fluid. We do not always 

 succeed in meeting with such homogeneous plates, that when 

 in the beginning everything has been equalized, equilibrium 

 shall exist between the pairs of plates of the one and the 

 other side. Frequently, previous to the addition of the acid 

 in the cells of the one system, a certain side, in which the 

 pairs have a somewhat more powerful electro-motive state, 

 has an ascendency, although if proper precautions have been 

 taken this is very weak. In this case, however, the experi- 

 ment can be rendered available for our purpose quite as well 

 by adding at present the acid to that series of cells which ap- 

 pears to be the weakest. According to the chemical theory, 

 the divergence of the multiplier should now quickly be re- 

 versed, instead of which it increases in the very direction which 

 it previously had. 



I will add yet the following variation of this experiment, 

 connected with a measurement. 



On one side five pairs of zinc and copper plates werearranged 

 in a couronne des tasses, on the other five pairs of zinc and tin 

 plates. The vessels of the first system were now filled only 

 a third part as high as those of the second, the first with 

 common spring water, the latter with strongly acidulated 

 water, which caused a very lively development of gas. The 

 first five plates connected by themselves into a circuit gave 



