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LXXI V. On Galvanic Circuits composed of two Fluids, and of 
two Metals not in contact. By Professor J. C. Poggen- 
DORFF.* * * § 
I N support of the so-called Chemical Theory of galvanism^ or 
rather of that view which places the source of voltaic electricity 
solely in the chemical affinity of the positive metal of the circuit, 
viz. the zinc, for the electro-negative constituent of the fluid, Mr. 
Faraday has of late brought forward in an especial manner the 
three following arguments : — 
1. The production of a spark on completing the junction of a 
simple circuit. 
2. The electrolytic law. 
3. The preponderance of a circuit of zinc, platina, and sul- 
phuric acid, over one formed of the same metals and a so- 
lution of the iodide of potassium. 
With respect to the first point, the production of a spark 
on making the connexion between a single pair of plates, 
Faraday, in the Eighth Series of his Experimental Researches, 
lays much stress upon it, and for this reason ; — because it must 
have passed before the metals could have come into contact, 
and thus not only proves its origin from pure chemical forces, 
but also the superfluousness of metallic contact for exciting 
voltaic electricity t ; in the further progress of his labours the 
English philosopher seems, however, to have some doubt as to 
the reality of a spark on junction ; at least he expresses himself 
in his ninth series in a manner which induces the belief that he 
considers this spark to be a heating and ignition of the mer- 
cury employed in the experiment at or after the moment of 
j unction J. 
Moreover, Professor Jacobi, in an experiment performed for 
the very purpose of solving this doubt, in which the wire of junc- 
tion of a simple, very powerful zinc-platina circuit was interrupt- 
ed by a layer of air only 0*00005 inch, was not able to perceive 
the least sign of the passing of a spark at the place of dis- 
junction §, And recently Professor Draper, in New York, could 
not even observe the spark in a perfect vacuum before direct 
contact between the mercury and the wire which formed the arc 
of junction of a simple circuit |1. 
* From Poggendorff ’s Annalen, vol. xlix. January, 1840: translated by 
Mr. W. Francis. 
t Experimental Researches, Ser. viii. §. 915. 
+ lUd. §. 1074. 
§ London and Edinburgh Philosophical Magazine, vol. xiii. p. 401. 
II JMd, vol. XV. p. 349. 
