ON STANDARDS OF ELECTRICAL RESISTANCE. 129 
Length ‘“ mm.; diameter 0-627 mm, 
(9 Copper ........ 89-7 ” Conducting power. 
DMS ca c's Os b 10:3 Li: 0 10-1386 
Made from pure metals. 55°) 9:8710 
Hard-drawn. 100-0 9:6526 
A=10-212—0-0068043¢+ 0-000012102. 
These alloys are given, as they approach in composition to that of ordinary 
gun-metal. 
(10) Gun-metal (Austrian). Length es 5mm.; diameter 0650 mm, 
Copper. ” Conducting power. 
Zine. 1 0 26°336 
Tron. 56:5 24-056 
A specimen obtained through 100-0 22-121 
the kindness of Mr. F. Abel. 
Hard-drawn. 
A=27-084—0-058750¢ + 0:00009116#. 
The conducting power of this alloy increased by heating to 100° for one 
day 5*7 per cent.—a larger increment than has been observed with any alloy. 
Generally, the conducting power of an alloy either remains constant or only 
varies 0-1 or 0-2 per cent. under the same conditions. 
Length 1564 mm. ; diameter 0-525 mm. 
(11) Proof gold. ay Conducting power, 
Hard-drawn. 15:0 68-969 
57°5 60179 
100-0 53°387 
A=72:548—0-24692¢+ 0:00055312, 
Length 2328 mm. ; diameter 0:525 mm. 
(12) Standard silver. su * Conducting power, 
Hard-drawn. 12:0 78015 
56:0 69-301 
100-0 61-949 
A= 80-628—0:22196¢+ 0:00035182?, 
In the following Table I have given the results here obtained, with those 
of last year, in such a manner that they may be easily compared :— 
Conducting | Percentage de- 
power crement in con- 
at 0°. ducting power 
: between 0° & 100° 
TES. 2% Siattag ciel ol éralsa, ahd sale del « fdlale 16°81 39-2 
EMMA or Ale .'si5 Shales Geese aed oa 9-16 31-4 
Other pure metals in a solid state .......... aster. 29°3 
Bebe With 1S p.c. on i. ove Lie cease 2°76 27-9 
MRED. 0.252 Pin) Lcdets (erate tetaidte & Sialy W GLa a's aes 72-55 26-4 
MMMPREO SUVER xi 5k fed ode) Hel edd clad wot ele #2 80-63 23:2, 
Gun-metal (Austrian) ............000 eee 27-08 18:3 
mere VO. p.c.cIPOM si iedeia le fbd hele a obatanks 2-06 17-5 
Gold, with 14-3 p.c. silver and 7-4 p.c. copper| 44:47 15:5 
Mopper, with 36-7 p.c. zinc .......6...6..-- 22:27 12-4 
‘Copper, with 25 p.c. zinc. ....66.80 0.2. e eee 22-08 11:5 
* Proc. Roy. Soe, xii. 472, 1863. 
1863. K 
