494 M. Poggendorff on Galvanic Circuits composed of 



the signs of inequality express which of the two fluids {a and b, 

 fig. 1, page 489) developes the strongest electronriotive force 

 when a pair of plates of the metals stated at the head of the 

 column are immersed in them. The expression s<C w, for in- 

 stance, in the space common to the columns zinc-silver, and 

 hydrochloric acid water, indicates that in contact with zinc and 

 silver the water excites a greater electromotive force than the 

 hydrochloric acid-, or, in other words, that the current has a 

 direction as if the zinc plate in the water were positive to the 

 zinc plate immersed in the acid, the word positive being taken 

 in the sense previously mentioned. 



I might also have added to the direction of the current, or 

 the direction of the magnetic deflections, their magnitudes, as I 

 always noted them carefully. But I have omitted thisj on 

 the one hand, because the intensity of the current is no mea- 

 sure of the difference of the electromotive forces under con- 

 sideration, and also because in the present case it is at the 

 same time a very variable element. In general the intensity of 

 the current in this kind of circuits is most powerful in the first 

 moment, and then rapidly decreases ; the amount and velocity 

 of the decrease vaiy however considerably. This causes among 

 other things that in two cases the diflerence of the two first de- 

 flections of the needle, to the right and to the left, may indeed 

 be equal, but the magnitudes of the deflections differ consider- 

 ably. In the one case these deflections amounted perhaps to 

 10° and 8°, in the other to 30° and 28°. In general the inten- 

 sity of the cui'rent only descends to zero, but at times it also 

 increases towards the opposite side. Sometimes this reversion 

 of the current takes place so rapidly, that, for example, the 

 first deflection of the needle, perhaps of 50° to the right, is im- 

 mediatety succeeded by one on the left of 70°. Now and then 

 the intensity of the cun-ent is but feeble in the first moment, 

 increases then for a time, and then gradually sinks to zero. 

 Such variations render a numerical comparison of the intensity 

 of the current in the different cases quite impossible, especially 

 as in general, on the repetition of one and the same experiment, 

 highly different values are obtained for the magnitudes of the 

 deflections. I have therefore merely stated in general, in the 

 notes to the Table, when the current was especially strong or 

 feeble : when reversions of the current result, they are for the 

 most part already indicated in the Table by the signs of in- 

 equahty placed beneath one another. 



