WIEDEMANN ON THE MOTION OF LIQUIDS^ ETC. 233 



Then again the mechanical action of the galvanic current mani- 

 fests itself in the transference of material particles at places 

 where, for a short distance, the circuit is interrupted by a non- 

 conductor; in the galvanic sparks and arcs of light, which are 

 always accompanied by a motion of the incandescent particles 

 of the conductor, at the place of interruption. Many attempts 

 have been made to establish a connexion between this phaeno- 

 menon and the direction of the galvanic current producing the 

 arc ; in particular, it has been thought that a motion of the par- 

 ticles from the positive towards the negative conductor was per- 

 ceptible; nevertheless, later experiments — for instance, those 

 of Van Breda and Matteucci — have proved that these phaeno- 

 mena can always be explained by the different intensity of heat, 

 and hence different state of fusion, of the ends of the two poles : 

 this is the more probable, inasmuch as these phaenomena are 

 seen only in gases which, at high temperatures, exert a chemical 

 influence on the substance of the polar wires. A transference 

 of matter in the voltaic arc, according to a fixed direction, is not 

 therefore established with certainty ; and perhaps the action of 

 the galvanic current here may be analogous to that of friction al 

 electricity ; for by means of the sparks produced by the latter, 

 the material particles are moved in one direction as well as in 

 the other. 



Nevertheless, just as in frictional electricity, a certain difference 

 in mechanical action manifests itself, depending on the direction 

 of the two opposite electricities (no matter whether this be ob- 

 servable in the different facility with which a brush of light may 

 be produced at points by means of positive or negative electricity, 

 or whether it be in the different Lichtenberg's figures which 

 positive and negative electricity separately produce), so also in 

 a galvanic current a similar difference can with certainty be 

 proved. When liquids are introduced into the circuit, this dif- 

 ference shows itself by a motion of the liquid particles in the 

 direction from the positive towards the negative pole. This 

 phaenomenon, which under certain circumstances can be ren- 

 dered visible, was observed a long time ago, but has never yet 

 been made the subject of a separate and closer examination*. 



* The few experiments which bear upon the subject considered in the pre- 

 sent memoir, were collected in a note by PoggendorfF at the time of Daniell's 



SCIEN. MEM.— Nat. Phil. Vol. I. Part III. S 



