S DE. A. MATTHIESSEN AND M. VON BOSE ON THE INFLUENCE OF 
These values have been reduced by using a formula which is the mean of the six 
deduced from the experiments ; for although there is a difference in the formula obtained 
for the annealed and hard-drawn (or rather partially annealed) wires, yet it is so small 
that they may be considered the same, more especially as the difference between the 
one obtained for the different wires is far greater. Taking the mean of the above values, 
and assuming the influence of temperature on the conducting power of hard-drawn and 
annealed wires to be the same, we find the following formulae : — 
For hard-drawn wires X^r^lOO’OO — 0’38287^-|-0‘0009848^^. 
For annealed wires X=108-574— 0-41570^-|-0-0010624^*. 
Copper. 
Wires 1 and 2 were of the same piece of electrotype copper prepared for us by 
Dr. H. MtiLLEE at Messrs. De la Rue and Co.’s. Wire 3 was cut off a piece of com- 
mercial electrotype copper from the same source. Table III. shows the results obtained 
with these wires. 
Table III. 
First wire. 
Second wire. 
Third wire. 
Hard drawn. 
Annealed. 
Hard drawn. 
Annealed. 
Hard drawn. 
Annealed. 
Length 
2262 millinis. 
0'691 millini. 
2245-5 niillims. 
0-691 millim. 
1753 miilims. 
0-598 millim. 
1738 miilims. 
0-598 millim. 
1476 miilims. 
0-537 millim. 
1461 miilims. 
0-537 millim. 
Diameter 
Conducting power 
found before heat- 
ing thehard-drawn 
wires 
^ Eeduced to 0°. 
95- 672 at 10-6 99-526 
96- 324 at 9-9 99-943 
96-750 at il-8 101-097 
96- 914 at 12-2 101-418 
97- 950 at 9-8 101-671 
98- 437 at 8-7 101-682 

0 Eeduced to 0°. 
94-355 at 15-0 100-021 
94-965 at 13-2 99-971 
94-880 at 14-2 100-268 
94-501 at 15-9 100-524 
94- 153 at 17-2 100-656 
95- 570 at 14-4 101-074 
94-327 at 18-2 101-230 
96- 575 at 12-7 101-469 
^ Eeduced to 0°. 
92- 568 at 20-6 100-327 
93- 263 at 19-0 100-461 
93-720 at 18-0 100-563 
93-434 at 19-0 100-645 
93-278 at 19-6 IOO-7O8 
92-865 at 20-6 100-649 
92-738 at 21-1 100-705 
Conducting power 
after being kept at 
100° for 1 day ... 
Ditto, for 2 days ... 
Ditto, for 3 days ... 
Ditto, for 4 days... 
Ditto, for 5 days... 
Ditto, for 6 days ... 
Ditto, for 7 days... 
The means of the conducting powers found for each of the following temperatures 
were — 
