Mr. J. N. Hearder on Electrical Conductivity. 17 
employed in each experiment was 3°5 inches, and its size about 
No. 26 wire-gauge. The numbers given are the mean of six 
experiments, the variation in them not exceeding more than 2 
or 3 degrees :— 
Metal employed in Degrees of heat on scale 
thermo-electrometer. of thermo-electrometer. 
Silver . ECR: 
2.02 re aah 7) 
LATS SR Saat eeraaae? 
LOOT Nitta tap 2: 
nh eT os Ae 
jg TT ee nS ale 
ae ca Lc aie Ee 
ET Oa RRR 
SS 26 
These experiments were repeated at different times with the 
same wires and with the same relative results, 
Since the best conductors were the most heated in these ex- 
periments, it seemed to follow that, with any single metal, larger 
wires would be heated more than small ones ; and this I found 
to be the case up to the largest size that could be inserted into 
the electrometer, viz. No. 15 wire-gauge. I regret that a scale 
of these results with copper wires from No. 15 to No. 36 has 
been lost, but it showed a curious coincidence between the tem- 
perature and the mass of metal. This remarkable inversion of 
their relative order as compared with the results obtained by the 
Leyden discharge, whilst it showed a consistency with itself 
which left no room to attribute it to any error in manipulation, 
yet seemed to exhibit such an inconsistency with preconceived 
notions of the laws of electrical conduction, that T'was induced 
to vary the experiments in the followin g manner. 
Instead of introducing the several metallic wires in succession 
into the bulb of the thermo-electrometer, I used them externally, 
causing them to form part of the circuit between it and the bat- 
tery, and employing in the electrometer simply a copper wire 
much stouter than those under examination. The following 
Table gives the results, the same wires being used as before :-— 
Wires in circuit between Degrees on 
battery and thermometer. thermometer. 
im, SR ee 
Copper. . . . . 128 
Pe). Td: bow. iep 
Berries 9 tld iss | eee 
Baste) a fan “Sow 
fe Pee 
Platinum. . . . . 60 
ee bee 
Lead. . 33 
Phil. Mag. 8. 4. Vol. 19. No, 124. Jan. 1860. C 
