320 
Te Be XIV. | 
Linear variation of the HALL effect 
for Bi,7, in strong fields T= 20°.3 K. 
| 
Jel | RH Obs. RH Calc. 
3450 230105 229103 
| 5660 350 352 
| 7160 431 434 
8520 503 507 
9880 583 582 
11090 647.5 647 
12090 700 102 
a! = al e-FT. : mee 
Within the temperature region 90° K.> 7214°K. A much more 
complicated formula would be required to embrace the observations 
at higher temperatures as well. 
On going down to liquid hydrogen temperatures the constant 5’, 
the maximum value of the second BrcQqveren component, which is 
negative at ordinary temperature becomes positive in the case of 
Bir and Birr. BuckMan’s investigations upon the same plates at the 
temperature of liquid air show that the reversal of the sign must 
take place below 72° K. 
6. With regard to crystals we have already stated in § 13 that, 
when the crystalline axis is perpendicular to the field, the Haun effect 
is negative at ordinary temperature, and approaches a limiting value. 
To this we may now add that with another rod also with its axis 
perpendicular to the field we found, at ordinary temperature, a maxi- 
mum at H == 9500, and then a decrease (10-3 RH fell from 37 to 
39,4); this leads us to suspect that proceeding to stronger fields than 
those we employed would have brought to light the same behaviour in 
the case of the rod quoted in $ 18. At hydrogen temperatures the sign 
of the Haut effect reverses and becomes positive, increasing linearly with 
the field for fields above 3 kilogauss*). From this it appears that in 
') J. BrecquerReL draws attention to the fact that at low temperatures RH 
becomes very large. The values we here give for hydrogen temperatures make 
this all the more striking. For Bi, we obtained RH = 500. 10° for H = 8500. 
With this plate, indeed, at the temperature 7’= 90° K. we get a higher value 
(RH = 214.10' for H= 8500) than that given by BrcQueReEL for his plates. 
From his data (loc. cit.) we calculate for the temperature of liquid air RH = 168, 103 
(or R=+19.8) for H=8500. 
