202 J. A. POLLOCK AND A. B. B. RANCLAUD. 
held by large blocks of carbon A and B, (not shown in 
elevation), through which the heating current passes. The 
cool carbon rod D is fixed in a holder E which can be moved 
Rico: 
- 
aes 
H 
aes “S 
¢: i Br Car c 
coo eo a 
; if <A DS 
Soe Se | ee 
Elevation. 
VDI fapea) = 
in the direction of its length by turning the nut F, the 
latter being prevented from longitudinal movement by the 
stop G. The holder EH is attached toa cross piece provided 
with an adjustable stop H, the cross piece working on pivots 
so that the cool carbon rod D can be very quickly placed 
in position before the heated cylinder C or readily removed. 
A scheme of the connections is shown in figure 2, where 
A and B are storage cell batteries, G a galvanometer, and 
Pa potentiometer; by this arrangement any difference of 
potential desired could be set up between H and C, allow- 
