THERMO-ELECTRIC PROPERTIES OF CHARCOAL AND CERTAIN ALLOYS. 341 



TABLE XIV. 
Temperature. M-N Deflection. 
1352 C. 0 
32°'8 9 
1559 67 
2011 885 
216°4 96 




These observations give us the equation 
6, = const. + 472847. 
Hence 
dé, wae: 
at 47284. 
The line is laid down on Plate XXI. Its equation is 
y =— 0153t + 6°64. 
The magnesium line (after Tarr) will be found on our diagram. The line of 
the alloy is near it, but its inclination to the lead line is different. The thallium 
line is not yet determined. 
The unit of electromotive force which we employed in the above was 
an arbitrary unit. It was necessary then to find its value. For this pur- 
pose we used a DANIELL’s cell, consisting of a plate of copper dipping in a 
solution of pure copper sulphate whose density was 1:125, and a plate of amal- 
gamated zinc dipping in a solution of zinc sulphate (free from iron), whose 
density was 1:098. The temperature of the solutions was about 11°C. We 
compared the deflection produced in the same galvanometer, when the current 
from the shunted cell was sent through it, with that caused by the current 
of the M-N thermo-electric circuit with the junctions at definite temperatures. 
The following are the measurements made :— 
(1.) Circuit containing Daniell’s Cell. 
Resistance of galvanometer, ; ; = 22°588 ohms. 
Resistance of wire in circuit, ; ; 3 = 20,000°08 
” 

Average of several 
Resistance of Shunt. Denecona 


1 ohm. 134-2 
Dries 222 
D5, 365°8 



_ VOL. XXVIII. PART II. 40 
