128 FE. H. Hali—Rotation of the Equipotential Lines 
Results obtained with these two strips are shown in the fol- 
lowing ta 
Date. Te mp. M. 0. RP. 
No. 1. Nov. 24. 18°7° 1647 0970 + +12000X 10 
s “3 2°5 1629 = 1007. +:11230x “ 
16°2 
Decrease for 1° fall of temperature, approximately ‘4 per cent. 
No. 2. Dee. 1. 18°° 1602 0870 +32720X 10" 
28 * 19 1587 0908 +30800X * 
1920 
Decrease for 1° fall of temperature, approximately ‘4 per cent. 
The magnitude of the rotational coefficient in the soft steé 
is about 14 times, and that in tempered steel about 4 times as 
reat as that in the soft iron. is agrees very well with the 
conclusion drawn from the hasty experiments of the year be 
fore, when a piece of steel from a clock-spring was used. 
When a sensitive galvanometer is used, an ordinary permanent 
horse-shoe magnet of half inch bar produces an easily discern 
ble effect in the strip of tempered steel. : 
It should be stated that two or three months before the trials 
which furnished this table were made, both these steel strips 
had been subjected, in the usual position, to a magnetizing force 
of about 8500 intensity. It does not seem probable that the 
results just recorded were seriously affected by this previous 
experience of the steel. nae 
is first inagnetization was for the purpose of detecting, if 
possible, a permanent effect, such as had been observed a yea 
before in a piece of tempered clock-spring, but had been vainly 
obtained with the tempered clock-spring. No. 1 showed @ 
permanent effect relatively, and even absolutely, larger that 
that in No. 2. It was about 5 per cent of the temporary effect. 
. 
observed that residual magnetization is, under certain condi 
test for permanent effect. The strip used was the one expel 
mented with the yea ore, a ipti 
already been published (this Journal, March, 1883). The per — 
manent effect, if any was produced, must have been a V@F. 
small part of one per cent of the temporary effect. a 
