294? Existence of electric Currents 



germination (or during the conversion of its starch into 

 sugar), may be compared to the negative plate of a voltaic 

 pile ; for, in addition to other phenomena, we find an acid 

 developed at its surface. It may be doubted by many 

 whether the weak voltaic current established during germin- 

 ation is of sufficient intensity to entitle it to be regarded as 

 the effect or cause of the chemical changes before alluded to. 

 It is now, however, well known that currents of the lowest 

 intensity (if the time during which they are in action be not 

 limited) are sufficiently energetic to produce most important 

 chemical changes ; and I think I am fully borne out by 

 experiment in asserting, that an electric current, from what- 

 ever source it may originate, is able to effect the decom- 

 position of any compound body capable of conducting it. 

 This opinion, however, of itself, would possess but little 

 weight, if it were not fully supported by the known action of 

 currents of the feeblest intensity on some of the proximate 

 principles of vegetables. I shall confine myself to the action 

 of these currents on starch, as it is the alteration which takes 

 place in this principle during germination that I have more 

 particularly considered in my last communication. 



From many experiments, illustrative of the general subject 

 of this paper, I shall select one of M. Becquerel's*, which I 

 have carefully repeated, and which has an immediate refer- 

 ence to the changes to which amylaceous matter is subjected 

 during germination. When a disc of copper is soldered to 

 one of zinc by its flat surface, and the compound disc plunged 

 into distilled water, an exceedingly feeble current of electricity 

 is set in motion, proceeding from the copper to the zinc, 

 thence to the water, by which it is communicated to the 

 copper, and so on in a succession of circles, or electric tides, 

 if I may be allowed the expression. Let two of these com- 

 pound discs be placed in separate glass cups, in different posi- 

 tions, the copper surface being uppermost in one, and the 

 zinc surface in the other ; and place on the upper surface of 

 either disc a piece of bibulous paper, on which some potato 

 starch has been scattered ; then fill the glass cups with dis- 

 tilled water, care being taken that the discs are completely 

 immersed. In the space of twelve hours, it will be found that 

 the starch on the copper surface of the disc will exert an 

 alkaline reaction on reddened litmus ; while the starch on the 

 zinc surface will turn blue litmus paper to red, demonstrating 

 the evolution of an acid on the zinc, and of an alkali on the 

 copper, surface of the compound disc. It will scarcely be 



* Traite de l'E'lectricite et du Magnetisme, torn. iv. p. 175. 



