THERMO-ELECTRIC PROPERTIES OF CHARCOAL AND CERTAIN ALLOYS. 331 
and two points being determined of the AgPd,,; line, its line is determined. It 
will be found in Plate X XI. Its equation is found to be 
y= —1865t—35°2 
Along with the lines for these alloys we give in the diagram those of silver 
and palladium (after Tarr). We may notice that the alloy lines lie between 
those of the metals. But they resemble in position and in general relation to 
others much more that of palladium than that of silver, although they contain 
a much greater proportion of the latter than of the former metal. The specific 
heat of electricity of both alloys is negative, that of palladium being negative, 
that of silver positive. 
Platinum-Iridium Alloys. 
We have investigated four, in which the percentages of iridium were 6, 10, 
15, 20 respectively, and, as above, two ata time. We give in Table V. the results 
of our observations on the first two, viz., the alloys PtIr, and PtIr,. The 
N wire of each alloy circuit was connected with the same terminal of the gal- 
vanometer as the N wire of the M-N circuit. The temperature of the beakers 
was constantly 13:4° C. 


TABLE V. 
PtIr.-N Deflections. PtIr,,-N Deflections. 
M-N Temperature. : as: 
Deflections. Observed. Calculated. Observed. Calculated. 
2 753 DOO Cal ene 255:2 +32°5 334 
66°8 36277 232°) 233 oe oe 
62°8 341°8 2335 2139 Bil Sy 
58:5 319°7 195 1944 30 29°9 
558 305°3 182°8 182°1 29 29-1 
52:8 289°9 168°8 169°2 28 28:1 
47°6 262°7 147°3 TAT 26°5 26:1 
43°3 240 130°5 1301 25 24°4. 
40°5 226 118°7 119.9 23°6 23°2 
36°3 204:2 105°8 104°3 Died Zilles 
By) 184-2 91:5 90°7 20 19°5 
29°5 169°4 80 81 18 18:1 
24°3 TAZ 63°5 64:1 15 153 
20 119°8 5L5 50°9 AT 12:9 
16°5 101°3 41°3 40°6 10°5 10:8 
13'8 86°6 B32 32'°8 9 8:8 
10°5 69°5 26:5 241 Sor 6:9 
8°8 60 Ds5 19°4 De 5:8 
6 45:9 2 12°8 4. 4. 



Table VI. gives observations which enable us to find the temperatures 
given in the 2d column of Table V., and to find the rate of variation of the 
deflections of the M-N circuit with the temperature of the heated junction :— 
