ON STANDARDS OF ELECTRICAL RESISTANCE, 137 
components,—I at once foresaw that it would be useless, as was afterwards 
proved by the research made in conjunction with Dr. Vogt, to make any 
experiments with the two metal-alloys, which may be. looked upon as a 
solution of one metal in the other, as no practical alloy would be found 
which would vary in its conducting power between 0° and 100° to a small 
extent. It must also be borne in mind that the alloy sought for must be a 
ductile one, capable of being drawn into wire, not too soft, as would 
easily be damaged by covering and winding, easily produced, and cheap in 
price. Bearing this in mind, we turned our attention to some three metal- 
alloys, thinking that we had some chance there of obtaining a good result ; 
for it is well known that the conducting power of German-silyer wire varies 
in such a slight extent between 0° and 100°. 
It also appeared worth while to experiment with some of those alloys 
which may perhaps be considered chemical combinations, or to contain such, 
as, for instance, platinum and silver ; and, on account of their other physical 
properties, the platinum-iridium alloys were also experimented with. 
In the following Table I give the results obtained in conjunction with Dr, 
Vogt. The unit here taken for comparison is that of a hard-drawn silver 
wire at 0°. The normal wires were made of German silver, and in order 
to obtain their values in terms of hard-drawn silver, they were compared 
with the gold-silver alloy. In these experiments it was thought better 
first to use those pure metals which are easily obtained, so as to learn some- 
thing regarding the manner in which the three metal-alloys behave, and 
then try some alloys made of the cheaper commercial metals. As will be seen 
by the Table, only the first part has been as yet carried out. 
TABLE. 
(With each series, the formula deduced from the observations for the corree- 
tion of the conducting power of the alloy for temperature is given, when ) is 
equal to the conducting power at the temperature ¢ C.) 
Composition of alloy. | Weight. Length 532 mm. ; diameter 0°625 mm. 
(1) olde, Aes): 58°3 Conducting power. 
Copper .... 26:5 Ts Found. 
Silver .... 15:2 9:0 11-956 
Made from pure metals. 53°5 11-674 
Hard-drawn. 100: 11-438 
A=12:017—0:0069033¢+ 0-00001112. 
This alloy was taken as Karmarsch states it is the hardest and most elastic 
of all the gold-silyer-copper alloys. 
Length 341-5 mm, ; diameter 0-618 mm. 
(2) Golds io 28 66-5 Conducting power. 
SU Gs a 18-1 TD. Found. 
Copper .... 15-4 10:95 10:5637 
Made of pure metals, 33°52 10-4341 
Hard-drawn. 55:15 10-3130 
78:35 10-1846 
97°52 10-0852 
A =10-6220 —0-0056248¢+ 0-00000098632. 
This alloy was tried as it corresponded to equal volumes of gold-copper 
and gold-silver, and these again correspond to an alloy possessing the lowest 
conducting power of any of those made of gold-copper or gold-silver. 
