( 232 ) 
3. The Harr-effect in electrolytic bismuth. The plate is obtained 
n the way described in Comm. N°. 42 U). 
The method of observation is the same as in all the previous 
experiments, and was described in Comm. N°. 26%). The plate car- 
rier / is made of ebonite. 
The leads for the HALL-current zj 7g are only 0.1 mm. thick, in 
order that they may conduct as little heat as possible, the larger 
resistance being immaterial. The wires mj mg supplying the primary 
current of about 0.5 amp. were chosen somewhat thicker, 0.25 mm., 
in order to decrease the heat produced in the liquid without in- 
creasing too much the heat conducted to it. 
The following results were obtained for the coefficient of HALL 
R and the product RM (M = Magnetic force). 
MAGNETIC FO RC &, 
Temp. 
3900 
2600 5000 | 5800 
R ea | R na] R | RM 
R nar] ru | R ORM 
+ 15° |] 11,2 | 14,5 | 10,9 | 28,2 | 70,0 | 39,0 | 9,4 | 47,0 | 9,1 | 52,7 | — -- 
— 90e 21,1 | 97,41 — | — [27,7 16901 — | — 145,8 | 91,4 [24,6 | 118,0 
(RM was expressed in the unit 1000 C.G S.) 
Hence in all fields the Harr-effeet has been increased, especially 
in the weakest field. The latter particular was also observed before *) 
with other bismuth for temperatures ranging from 20°C. to 100°C. 
The coefficient of Hatt at — 90° C. in a field of 1300 C.G.S. 
units is 21,1 and exceeds by far the highest value formerly obtained. 
The question delt with in several earlier communications, as to 
whether or no a maximum Harr-effect exists at low temperatures, 
is not definitely answered by these measurements at only two tem- 
peratures, but the rapid increase points to the contrary. A more 
decisive answer will be obtained I hope before long by repeating 
the experiment in a bath of liquid oxygen. 
The figures communicated for the temperature — 90°C. are not 
yet quite final, as the contact-resistance at the secondary electrodes 
1) Versl. 25 Juni °98, p. 98. Comm. NO. 42, p. 7. 
2) Versl. 30 Mei °96, p. 47. Comm. NO. 26, p. 3. 
*) Versl. 30 Mei 96, p. 5. Comm. N° 26, p. 20. 
