321 
the case of the axis perpendicular to the field, the positive effect 
must be much weaker at ordinary temperature than the negative, 
and begins to be appreciable only at very low temperatures. What 
we haye found for the case of the axis perpendicular to the field 
is analogous to what BercqurreL obtained with the axis parallel to 
the field. 
With our erystalline rod placed in a definite position the value 
of the field at which the second component attains saturation at 
hydrogen temperatures is the same as that at which a plate con- 
sisting of crystals of various orientations (for instance, a plate of 
compressed electrolytic bismuth) reaches saturation. That is to say, on 
going down to hydrogen temperatures, the saturation field appears 
to be independent of the orientation. 
§ 15. Linear variation of the increase of resistance of bismuth 
in strong fields. 
In $ 2 we remarked that in strong fields the resistance varied 
directly as the field. For fields of 12000 gauss upwards we find 
1 
w 
LD le | ne, eee eee 
ww 
(ef. fig. 1 of the Communication N°. 180a by Brner Beckman) where 
the values of a and 5 vary, greatly with peculiarities of the bismuth 
employed (wire or various plates made from compressed electrolytic 
bismuth). 
It is worth noting that the coefficient a of the linear variation 
of resistance, and the coefficient a’ of the linear variation of the 
Hart effect can, for temperatures below that of liquid air, be repre- 
sented by the same functions of the temperature, so that we may write 
re A be OR TE) 
This is found to be the case when we use the values given by 
Benet BrCKMAN for the temperature of liquid air (see sections 2 and 
3 of the Communication N°. 180«) in conjunction with those con- 
tained in Tables I, I], and Ill. If we remember that the values of 
8 and #' can differ greatly for the different plates, 
(for Bi,7 B= 0,023 and p' = 0,023 
Bi,u B = 0,014 oo == 0,006 
lant = 0.027) 
it is evident that we can as yet give no answer to the question 
as to whether the values of @ and p/ are the same or not for pure 
bismuth, and the agreement in the case of 7,7 can quite well be 
) ae =e 1 
” 
accidental. 
The constant 4, which is very small at ordinary temperature, 
becomes large and negative at hydrogen temperatures. 
