50 H. Haug on the Electro-motive Force 
24:97, elt: 92, as internal resistances. The mean value of all of 
out the platinum being red hot, against 5-77 of table 1x, with 
the platinum wire red hot indeed. At any rate the polarization 
cannot *~ a great part in the results of my experiments. 
aring the results of tables 1x to xIv, I get from the mean 
values ata following 
Table of ratio of ome of  Aiemaste poco manatee with constant addition of differ 
euit. 
wire in the circu 
——. ‘o ther "lResistances of columns (a); aor ae nast Pcie 
circui Lowest. Higher. — increase. resistances. increase. 
0 321 6°34 1°975 18°51 6 
25 em. 388 Lt 2°0038* 20°17 5°20 
2 4°33 849 | 1°961 20°67 477 
100 “ 5:02 9-79 : 1°95 21°30 4°24 
70 6-61 11°66 1764 22°24 3°36 
200°2* 7 65 12°94 1°691 23°44 3°06 
The table illustrates the dependence of the ratio of increase on — 
the manner the directly closed circuit is built up, on the greater 
or less intimacy of the contact, ete. 
In tables X to XIV, column (Cu) contains the resistances of the — 
respective lengths of copper wire. The increase of resistance 
maintains the same ratio as in the respective , columns (4a a). 
Using mean values, I derive, from comparing all five tables, the 
following results. 
‘ Length Resistance Respective Resistance Resp tive 
of copper at high resistance of at low resist ce of 
wire. intensity. 25 cin. length intensity. 25 cm length. 
25 5 “50 “2 99 
oo) ea 85 “425 1°666 833 
5 eed 16 "415 3°237 809 
160. .* 2-76 46 4°877 8138 
20 me 3°62 "452 6°12 "165 
The resistance of 25 cm. of copper wire, expressed in centi- 
meters of platinum wire, at high intensity, is rather irregular, 
the first value in particular being too great. It is, however, in 
agreement with all tie facts, safe to say that the resistance 
of a given length of copper wire, or the specific resistance, ap- 
pears the greater the longer the measured wire is. This is con- 
trary to what may be expected from the different influence of — 
temperature upon the resistances of copper and platinum, exem- 
plifying again the supposition that there is some other reason for — 
the increase of resistance in columns (a), overruling the influence 
of difference of temperature. At low intensities, the specific re- 
observation sb bi em, of co and 4 cm. of platinum wire in the 
aivaay boo oi on acto ‘this length © 
* The 
circuit, gives a ratio of increase comparativel 
of platinum wire having “been hotter than in any other 
