132 FE. H. Hall—Rotation of the Equipotential Lines 
the width of the poles of the magnet, a reversal such as Mr. 
Bidwell detected should not occur. 
Mr. Tomitnson’s SUGGESTION. 
No. ofexp. _ Date. Temp. M. 0. RP. 
a) 
1 July 28, "94; 22° 1717 03074 14940 x 10 
2 i 49° 1703 03135 13760 “ 
8 20; 20°5° 1652 = 03140 14710 
4 #80, 22° 1636 03123 i2810 “ 
5 ft 213° 1629 03121 15060 “ 
6.4: Angel, 98°. AGRI 03137 13180 “ 
7 ae 26°1° 1691. 03140 15110 “ 
8 ne 4°1° 1627 03112 13220 7 
Combining the Ist, 3d, 5th and 7th, we have 
Temp. BLP, 
22°5° 14960 x 10-* 
From the 2d, 4th, 6th and 8th we have 
3°5° 13240 x 10-* 
Decrease for 1° fall of temperature = approximately .6 pe 
c 
ent. 
It will be noticed that the results obtained at low temper 
tures do not accord so well as those at high temperatures — 
This fact is in all probability due to the difficulty experienced 
in preventing slight fluctuations of temperature while the colder 
water was flowing through the tank. Irregularity in the flow 
of this water causes disturbing thermo-electric currents. 
The quantity called R. P. in this paper corresponds to the 
= of my 1881 paper divided by the F of that paper. Calcul — 
ting the R. P. of nickel from the 188 experiments I find it © — 
