THERMO-ELECTRIC PROPERTIES OF CHARCOAL AND CERTAIN ALLOYS. 343 





TABLE XV. 
dy |. ; __ | & in terms of 10-6 eee a aie 
Substance. di (diagram unit).| A (diagram unit).| of a aia © | aie atin Cleans 
oe cell. | 
Charcoal . a -)290 + 20°54 — 00304 — ‘000193 
moPd,, . — 1240 =| 26'Go = “01302 — 000830 | 
Bord, . — ‘1865 — 35:20 — :01958 = 0 AES | 
or, — ‘1540 + 213 — ‘01617 — ‘001026 | 
pir, - — ‘0268 + 58-11 — ‘00281 — ‘000179 
obr. . + -0443 + 67°86 + 04651 + -000296 
oe + :0199 + 70°21 + -00209 + :000133 
mae. |. + ‘1490 — 41:06 + -01564 + -000991 
RpAS... — ‘2410 — 40:93 — ‘02530 — ‘001607 
MeTl ; — -0153 + 6:64 = OOn oil — 000102 







The above experiments were conducted during the summer months of 1877 
in the physical laboratory of the Edinburgh University. The alloys were kindly 
supplied us by Professor Tarr, at whose desire we undertook the investigations, 
and to whom we are indebted, not only for the use of his laboratory and appa- 
ratus, but also for his invaluable advice. 
In addition to the lines of the substances which form the subject of this 
paper, we give on the diagram the lines of the metals potassium, sodium, and 
cobalt. These were investigated experimentally in Professor Tart’s laboratory 
after the publication of the “First Approximation to a Thermo-Electric 
Diagram,” so that, though their positions were indicated in notes read before 
the Society in the years 1874 and 1876, they had not been presented graphi- 
cally on the diagram. They all lie below the lead line, and are inclined like 
iron and palladium; but the cobalt is so far down that its position relatively 
to palladium cannot be represented except ona diminished scale. Accordingly, 
in the lower right-hand corner of the diagram, a smaller diagram is constructed 
Which gives the relative positions of the iron, lead, palladium, nickel, and 
cobalt lines. The numerical constants are as follows :— 



d k in terms of 10-6 
Substance. ol A. of a DANIELL’S k (after Tair). 
at cell. 
Na 2539 = 26 — “0336 = 00213 | 
Pd — ‘27 — 47 — ‘0284 — ‘00182 L 
K — 10 — 84 — .0105 — ‘00067 | 
Co — 88 — 200 — ‘0924 — ‘00585 | 
i 





