46 Hi. Haug on the Electro-motive Force 
vation I . calculate upon the a of every two 
intensities. The results are contained in the vertical columns 
to the right of columns (a), of tables vir and pit In table vu, 
I further calculat e mean of the last five values of each 
vertical column from ‘@ to (b); and the mean value of all the 
other figures. e table shows unmistakably a general and great 
increase of the internal resistance with decrease of observed in- 
tensities. Comparing now the mean of the first five values of 
column (a), not with the mean of column (4) which may be too 
_ high, but with the mean of all the last figures, — is still less 
than the mean of 171°6 and 198-9; we get a ratio of increase 
of from 103-91 to 183-6; or 1 to 1 7 7; and this for a reduction 
of intensity from 1-982 to ‘7844, or from 2°58 to 1; and for a 
reduction of temperature of the unit of copper wire which I 
should not think at all sufficient to explain that rati 
In table vull, calculated in the same way, the mean n values at 
the foot of it embrace only the last three figures of each col- 
umn. Comparing here the mean of the first three figures of 
column (a) with the mean of the last two mean values, viz: 
15°81-+18: : 
~=17-08, in order to avoid any overrating, we get an 
increase of from 6:5 to 17-08, or from 1 to 2°63, which again can- 
not be accounted for solely by the difference of temperature of the 
unit of resistance. This ratio is therefore partly due to the ratio 
844 
of HE eey of intensity of the current which amounts to oe p 
equal 8°62 to 1. 
In table vt, with the copper wire rheochord, a reduction of 
intensity arnt and of temperature of the rheochord wire to 
an unknown ae are attended with an increase of internal re- 
sistance from 1 to1-77. In table vim, with the platinum wire 
rheochord, a reduction of intensity to —., and of temperature 
1 
8°62? 
of the rheochord wire to an extent much greater, I have no doubt, 
than in case of the copper wire, is followed by an increase of 
internal resistance not more than from 1 to 2: 68, being less, in 
proportion, than in ease of table vir. It therefore seems that 
the increase of internal resistance, as proceeding from difference 
of intensities, is greater at high intensities than at low intensi- 
ties of the current. And combining now the results of both 
tables, we find an increase of internal resistance from 1 to 1°77 X 
2°63, or from 1 to 4-655, this increase being due first to the re- 
duction of intensity from 1°982 to -091, and second to the dif- 
ference of temperature of the unit of resistance, which however 
could not produce half that ratio, I should thi nk. 
