153 
-.The values of A and n obtained for the different specimens are 
given in Table 1. For each specimen n = 1.74°'). 
A specimen was also prepared for investigation from another piece 
of Ceylon graphite out of the laboratory collection. This graphite 
very easily split up along its cleavage surfaces but pieces of uniform 
structure of suitable form were difficult to obtain. The best piece 
I could prepare gave an increase of resistance of only 182°/, in a 
field of 20 kilogauss, the resistance out of the field being 0.0427 Ohm. 
A piece of graphite from Himbuluwa (Ceylon), which was investi- 
gated, on the other hand, gave quite different results. The upper 
side of this graphite possessed a quite smooth and polished surface 
underneath which however it appeared to be of a fine granular 
structure. A thin piece of this upper layer was removed and the 
variation of its resistance found when transversely magnetised. An 
increase of resistance of 220°/, was observed in a field of 20 Kgs, 
the resistance out of the field being 0.0786 ohin. A thin piece removed 
from the under side of the same material, and having a high natural 
polish on both of its cleavage surfaces gave the anomalous results. 
Its resistance outside the field was several hundred ohms and diminished 
very rapidly with increase of temperature. In a magnetic field however 
no change in its resistance could be observed, while rough experi- 
ments indicated that it was apparently paramagnetic; no test for the 
presence of ferroginous impurities was made. 
Specimen G 12 was also tested with its cleavage plane parallel 
to a transverse field, the crystallic axis being therefore at right 
angles to the lines of force. In a field of 26 kgs the value R’/R, 
was found to be only 1,15 while for the usual position this ratio 
is rather more than 6. This evidently proves the necessity for very 
accurate adjustment of the angle between the erystallie and field 
axes’): an analogous question is known to arise in the behaviour 
of nickel and other ferromagnetic wires. 
EXPERIMENTS AT LOW AND HIGH TEMPERATURES. 
Observations were taken at temperatures of — 179°, 0°, + 18°, 
+ 95° and + 179°, the field being varied from 0 to 40 kilogauss. 
1, Within the experimental errors the exponent may also be nm =V 3 =1,732 
or n=7/4, 
2) The effect of longitudinal magnetisation was also observed. The increase of 
resistance involved was found to be independent of the direction of the current 
and of the same order as that observed in this last described position. Experiments 
are in progress to study the effect in both these cases at different temperatures. 
