492 M. PoggendorfF on Galvanic Circuits composed of 
drying with bibulous paper, or, if it seemed requisite, by rub- 
bing with sand-paper, scouring with sand and acids or water ; 
although these operations are exceedingly troublesome from 
frequent repetition, yet they were never neglected. Moreover, 
the platina was, previous to each experiment, heated over an 
alcohol lamp after having been cleansed, as it otherwise only 
produces weak effects. I therefore believe that the following 
results merit some confidence, especially as most of them are 
deduced from several experiments repeated on various days. 
Before, however, communicating these results, I must still 
add one remark. 
By whatever cause the electricity may be produced in cir- 
cuits of this kind, it is evident that there can be no doubt 
respecting the where, that it can only occur at the places of 
contact of the fluids with the metals, — since a contact of hete- 
rogeneous metals does not take place, or rather each of the two 
metallic slips contains two such contacts, which, from their 
being of opposite nature, must necessarily nullify each other. 
There are, therefore, in this kind of circuits four possible places 
of excitation, two in each vessel ; and if we combine the electro- 
motive force developed in each vessel, we have two such forces, 
e and d, which act in opposition to each other. If, moreover, 
we call r the total resistance of the circuit, then, according to 
Ohm^s fundamental law for the intensity of the resulting cur- 
e ”■ d 
rent, we obtain the expression — - — . 
Accordingly, the direction of the current, i, e. the direction of 
the deflection of the needle of the multiplier, depends solely on 
the sign of the difference e — d; on the other hand, the inten- 
sity of the current, or the magnitude of the deflection, both on 
the value of the difference e — d and on the value r of the 
resistance. The amount of the deflection of the needle affords 
gen, the temporarily negative one, so it seemed, always to a greater extent ; yet 
but few hubbies ascended from it. 
Amalgamated plates exhibit the same phaenomena ; hut since in this case 
stronger acid may be employed without giving rise to any disturbance, it can 
be observed that the mere raising one of the plates about one inch renders 
it considerably negative ; re-imrnersion again increases the negativeness. I 
observed this with sulphuric acid of 1-827 spec. gr. diluted with 9 times its 
volume of water, into which the plates were immersed to the depth of 2*5 inch. 
These enigmatical currents are all of them, however, but of transitory 
duration, and they can therefore, in the following experiments, in which 
the positive metal, situated in the acid, was in most cases immersed last, at the 
utmost have only effected the first deflections, and then only when these were 
feeble. But in general the heterogeneity which originates for the positive 
plates from the contact with two fluids, is far stronger. At times I have 
also convinced myself that the results were essentially the same, whether the 
positive plates were immersed at the same time, or one after the other, before 
or after the negative plates. 
