as a Standard of Electrical Resistance. 11 
The gold-silver alloy, however, only varies 0°3 per cent.,— 
another reason why the alloy may be drawn by anybody, and 
still have the same conducting power. 
The following experiments show the effect of an increase of 
temperature on the conducting power of this alloy. The details 
of the experiments, together with the apparatus employed, will 
be published shortly in a paper by Dr. von Bose and myself, 
“ On the Conducting Power of the Metalloids, Metals, and Alloys 
at different temperatures.” Our results at present do not agree 
with those of Arndtsen and Siemens, who state that the resist- 
ances of most metals vary in direct ratio with the increase 
of temperature, but with those of Lenz, who calculates the 
conducting powers for different temperatures by the formula 
N=a+yt+ z 7%, where x is the conducting power at 0° C., 
y and 2 constants. I may also mention that the metalloids 
conduct better on being heated, being the reverse of that which 
the metals do. | ets 
An annealed wire of No. 1 alloy was heated in a glass tube 
placed in a water-bath (a), and afterwards heated in an oil- 
bath (4). Its conducting power was determined at different 
temperatures ; and the values found are given in Table V. The 
values found for an annealed wire of No.5 alloy (c), heated in 
an oil-bath, are also added. 
Table V. 
(4.) (d.) (e.) 
Conducting Conducting Conducting 
T. power. T. power. T. power. 
0°4=15°053 9:°1=14°954 6°1=15:088 
19°5=14°854 30°9=14°728 33°3 =14:798 
41°3=14°626 java — 14°50) 51°6=14°607 
60°6=14°431 71°4=14°325 73°3=14391 
82°7=14°219 95°'1=14:094 96°7 =14°162 
100:0= 14°052 69°'4=14°342 73°3= 14391 
79°3 = 14°251 47°9=14°550 51°4=14°609 
59°1=14°453 30°8 = 14°730 31:7=14°811 
39°3=14'647 10°5=14°939 10°3=15°039 
17°9=14°865 
0°-7=15-049 
The diameter of (a) was 0°539 millim. and its length 683 
millims., and that of (c) 0-915 millim. and its length 987 
millims. 
Taking the mean of the two temperatures and conducting 
powers, and calculating (by the method of least squares) the 
probable values for 2, y, z for the formula X=2-+ yt+ 2é?, where 
A= conducting power z at ¢ degrees, 2 conducting power at 0° C., 
yand z constants, we find, ) 
