38 Ona Standard Measure of Resistance to Galvanic Currents. 
Table VI. 
Conducting power of the metals at the temperature ¢ compared 
with that of mercury at 0° C. 
1 
Mercury . 1+0:00095 .z (S). 
5°1554 
Lead ° 2 e e ° ~ ° 1+0:00376.¢ (A). 
8:257 
Platinum : ° ° 3 < e 1+0-00376.t (A. S). 
8°3401 
Iron ss + + + + + 740:00413.¢4-0-0000082718 (A). 
10°532 
ae T£0-000887.4—0-000000557.2 (A): 
annealed 4:°137 (S). 
Brass, hard << 4...) -s gla ws): 
7, annealed. : >". “her oue tO) 
14249 em, 
A 2 © 1 -0'00166.4—8-00000208.F- . 
Anca 31°726 
wea 1 +0-003638.¢° 
Ceppe: T+0003682 ‘4: 
% us beards. soa ‘dst: D2 ROARS). 
Be uannedied.. ay 2s. «is. Do eoo Ws). 
Silver, hard . OO ES aac AG 
1+0-0003414:.z 
yr) wannedleds:: o;!. 64°38 (8S). 
For convenience I have given Arndtsen’s results, together 
with the coefficients for correcting the resistances for the tempe- 
rature. Whether these are the same for annealed and unannealed 
wires I have not been able to determine. The brass that I experi- 
mented on was found on analysis to consist of 29°8 per cent. 
zinc, and 70:2 copper. 
In conclusion I should mention, for the benefit of those who 
may wish to make standard measures of resistance in the manner 
here described, that it 1s necessary to warm the mercury to be 
employed for several hours under a covering of concentrated sul- 
phuric acid mixed with a few drops of nitric acid, to get rid of 
all metallic impurities, as well as the free oxygen, which greatly 
increase its conducting power. 
