PROFESSOR THOMSON ON THE ELECTRO-DYNAMIC QUALITIES OF METALS. 667 
or from the last two of them without the first (°‘025 Cent.), was of the same kind as 
in the first two experiments. This experiment then conclusively demonstrated that 
the effect previously discovered was really owing to the heat in the central part of 
the conductor, and not to any inequality in the metal of the conductor itself, nor to 
any accidental disturbing agency. 
43. It was thus established, that the Resinous Electricity carries heat with it in an 
iron conductor. 
^§44 and 45. Experiment with Copper Conductor, repeated. 
44. The very small effect I had discovered of the opposite kind in the copper con- 
ductor required confirmation ; and indeed the analysis of the progress of the varia- 
tion (see Tables I. and II. § 56 below) was so unsatisfactory, that I felt it quite an 
open question, whether it was the true effect, or merely an accidental coincidence of 
irregularities; and I thought it improbable that contrary effects should really exist in 
copper and in iron. I made on the 26th of November another experiment on the 
copper conductor, with the current flowing six times eight minutes each way (instead 
of eight times six minutes, as before, because the analysis seemed to show that the 
effects which had chanced to appear in the average results of the six minutes might 
disappear with longer periods*) ; but I got still a very small result of the same kind. 
The full analysis (Table III.) was equally unsatisfactory with those of the two pre- 
ceding experiments on the same conductor. The following numbers show the tem- 
peratures at the reversals, and the final result, as in the previous abridged tables. 
45. Conductor composed of thirteen slips of sheet copper. 
Experiment V. November 26, 1853. 
(Current 
six times eight minutes in 
each direction.) Temperatures and 
Diminutions 
differences of temperature after eight minutes of current entering 
of differences 
from middles to 
Periods. 
By end next A. 
By end next B. 
ends of periods. 
Ta- 
Tb- 
Tb-Ta=D. 
Ta- 
Tb- 
Tb-Ta=D'. 
D'-D. 
I. 
50-88 
52-78 
i-90 
50-88 
52-72 
1-92 
--02 
II. 
50-64 
52-49 
1-85 
50-53 
52-32 
1-79 
-I--06 
III. 
50-38 
52-29 
1-91 
50-01 
52-00 
1-99 
— -08 
IV. 
50-14 
52-08 
1-94 
49-90 
51-83 
1-93 
+ -01 
V. 
49-60 
51-61 
2-01 
49-48 
51-52 
2-04 
— -03 
VI. 
49-11 
51-22 
2-11 
48-80 
50-92 
2-12 
— -01 
Means for five periods 
49-974 
51-938 
1-964 
49-744 
51-718 
1-974 
--01 
Augmentation of difference during periods included... *20 
Add average augmentation per half-period -l-0'02 
Effect due to reversal of current -Ol, 
in favour of Vitreous Electricity. 
* I now believe that a true effect, amounting to from °‘01 to °'02, was really reached in three or four 
minutes, and that in the latter parts of the half-periods there was no sensible augmentation of this effect, but 
MDCCCLVI. 4 T 
