126 REPORT—1863, 
The differences in the above are probably due to temperature; for as the 
wires are in tubes filled with carbonic-acid gas, we can never be absolutely 
sure that wire has exactly the same temperature as the bath. In properly 
made resistance-coils this source of error is materially diminished, and in 
some experiments which are about to be made to further test the electrical 
permanency of metals and alloys this source of error will be almost entirely 
obviated. It may be here again mentioned, that the reason of placing the 
wires in glass tubes filled with carbonic-acid gas was to obviate the oxidation 
of the metal or alloy by the oxygen of the air, or from the acids produced by 
the oxidation of the oil or fat with which the wires are covered when drawn, 
as the holes in the draw-plates are generally oiled or greased, &c. 
Those whose conducting power has changed are as follows :— 
Values taken from column 38, 
No. 1. Silver: hard-drawn .......... 103:915 
No. 3. Silver: hard-drawn .......... 102-807 
No. 5. Copper: hard-drawn.......... 100-248 
No. 7. Copper: hard-drawn .......... 100-149 
No. 8. Copper: annealed ............ 95°556 
No. 11. Gold: hard-drawn............ 99-869 
INO. [2. Gold. “annealed ©... omen ect 99-877 
No. 17. German silver: annealed ...... 100:162 
No. 18. German silver: annealed ...... 100:145 
No. 19. German silver: annealed ...... 100-217. 
The cause of the change in the conducting powers of the alloys Nos, 1, 3, 
5, 7 is undoubtedly due to their becoming somewhat annealed by age*, With 
No. 8 the alteration may be attributed to faulty soldering. That the con- 
ducting power of the German silver experimented with has altered is not a 
proof that all German silver will do so; for we find the gold wires Nos. 9 and 
10 not altered, but Nos. 11 and 12 (which were cut from the same piece, 
but of a different one from the one from which Nos. 9 and 10 were taken) 
have altered. Further experiments are, however, required to prove whether 
the metals and alloys given above as constant in their conducting power 
are so or not. 
Schroder van der Kolk statest that the conducting power of copper wire 
undergoes a change when even weak currents are allowed to pass through it. 
In order to see whether that of the above wires would suffer any change, 
the following experiment was arranged :—Nos. 1, 2, 5, 6, 9, 10, 18, 15, 17 
were connected together, and a current from two Bunsen’s cells was allowed 
to pass through them day and night for six days. The cells were cleaned 
every morning and evening, and the dilute sulphuric acid renewed. The ex- 
periment was carried out soon after, June 14, 1863. In the subjoined Table 
the conducting powers are given as found before and after the trial, com- 
pared with No, 19. 
Conducting power observed, as compared 
with No. 19=100. 
Before. AVS After. We 
No. 1........103°700 20-0 103:775 20-2 
Won 2 skein 99:740 20-1 99-733 20:2 
INOS Pe cre fatator ste 100:040 20:2 100:045 20-2 
No: “6 vateutetez 99-807 20:0 99:865 20-0 
Noi 9c nccnaare: 99-838 20-2 99-860 20-2 
No: TOs. eee 99°855 20:0 99:807 20:2 
* Brit. Assoc, Report, 1862, p. 189. + Pogg. Ann. 110, 452. 
