130 FE. H. Hall—Rotation of the Equipotential Lines 
It seems-probable that a thin slice of bismuth, properly pre- 
pared and mounted, will come to be a valuable instrument for 
measuring the intensity of strong magnetic fields. 
ANTIMONY, 
The powerful effect observed in bismuth suggested an exam- 
ination of antimony. A slice of this metal much like the slice 
of bismuth just mentioned was prepared. The cross suffere 
in shape a good deal in making the adjustment. The final 
average thickness in the central portion was estimated at 
2 mm. 
Date. Te M. C. R.P. 
1884, July 26th, 21°8° 1696 +1150 +114100x10-* 
Aug. 8th, “211° “1688 “1104 117800 .- 
Aug. 8th, 3° 1638 1104 +4+123900X ...- 
The two trials of August 8th were not entirely independent 
of each other, as only one test of the intensity of the magnetie 
field and of the sensitiveness of the Thomson galvanometer was 
made during the two trials of that date. The results as they 
stand indicate an increase of the rotational power with fall of 
temperature, but the experiments were too hasty to justify 4 
conclusion upon the matter. . 
eral experiments have resulted from the criticisms 
suggestions of other investigators. 
Mr. BroweEti’s TuEory. 
This has been so recently and so widely published that it 8 
hardly necessary for me to state it in detail. 
In Science (March 28th, 1884), I replied very briefly to Mr 
Bidwell’s first paper, stating that I found the transverse current 
in a strip of soft steel to be in the same direction when the 
strip was fastened to the supporting plate by a clamp across the 
middle of the strip only, as when it was fastened by means of 
tional effect.” In brief he obtains what he calls a “ reversal ” 
of the transverse effect in gold, using a strip of that metal hav- 
ing two narrow longitudinal slits lying on the same straight 
line and nearly meeting in the center of the strip. : 
I shall not undertake here an extended discussion of this 
interesting experiment of Mr. Bidwell. My view of the mah 
ter is in substance as follows: | 
