44 H. Haug on the Electro-motive Force 
With this object in view, I preferred to exchange the nitric 
acid for a properly acidulated solution of bichromate of potash, 
since a battery with this liquid, after having been used for some 
i s much less reliability as regards constancy than 
the Bunsen battery. The results of this series of experiments 
are re in tabl They are very irregular, from errors 
electro-motive force. For every external resistance two mean — 
values of the internal resistance are calculated, one from the first 
half, the other from the second half of the single observations. 
These mean values are: 
Forcentim. of — First Second For centim. of First Second 
platinnm in mean mean platinum in mean mean 
the circuit. value. value. the circuit. value. value. 
25°69 25°00 30 8735 84°37 
4 36°5 23°42 40 84-72 36°09 
6 83°34 31:08 60 41:37 39-76 
8 83°44 31°69 120 41°85 39°57 
10 3136 31°75 200 41°54 40:09 
20 85°27 84°66 - 
In nine out of eleven cases the mean values of the first ob- 
servations are greater than the mean values of the last observa- 
ions. From this fact I thought myself warranted to believe 
that all those circumstances together which may be considered 
as influential upon the results, generally tend to diminish the 
ratio of increase, or at least, t that in my experiments they would 
not inerease this ratio. I therefore considered the results of my 
Since the heating of the thin platinum wire of the reochord 
prevented me from observing higher intensities (those above 
tan, = 0°6), and ealeulating upon them, and since I was aware 
that the influence of temperature upon the resistance of con- 
dueters would prebably be, and has been, considered as suffi- 
cient to explain the inerease “of internal resistance, as proceeding 
from the commor method of calculation, I prepared myself a 
rather imperfect reochord with copper wire, because this metal 
jeanlte of experiments with this copper wire aecoeath 
resistances are expressed in centimeters of this copper wire. 
Experiments of table viil are made with the platinum wire rheo- 
