154 
The method of measurement was the same as at 18°; the deter- 
minations afforded no difficulty, the resistances being quite steady. 
At the lower and higher temperatures thermo-electric effects were 
sometimes evident but by successive reversals these were eliminated. 
It was incidentally observed that these thermo-electric effects — when 
occurring at the connections of the graphite and therefore within the 
magnetic field — were also influenced by the field *). Thus in one case 
the thermo-electric effect was increased fourfold by a field of 38 kgs. For 
all the specimens examined (with the exception of the piece from 
Himbuluwa) the resistance of the graphite out of the field was found 
to zncrease with the temperature, the coefficient of increase of resi- 
stance being of the order 0,001 per degree. The ordinary temperature 
curve = funcet. (0) for =O is given in Fig.2 for G15. Very 
ResisTANcl R ww O4Ms 
CHANGE or Resisrance 
TEMPERATURE 
——— 
Fy = 0 
EM PERATURE O 
Fig. 2. 
nearly the same type of curve was obtained in the case of specimen 
G11. It is interesting to compare this with the curves obtained by 
KAMERLINGE ONNES and Nernst’). The temperature during a series 
of readings, the graphite being in the field, was determined as 
follows. Before commencing, the current required to be sent in the 
reverse direction through the magnet to reduce the residual field to 
zero, was determined. Then, to measure the temperature, the graphite 
1) These effects are being subjected to further detailed investigation. 
2) H. Kameruincu Onnes, Versl. Afd. Nat. 19. p. 1187, 1911. W. Nernsr, Sitz. 
Ber. Berl. Akad. p. 306, 1911. 
