124 E. H. Hall—Rotation of the Hqwipotential Lines 
that this direct effect was small and I endeavored to arrange 
matters in such a way that it would affect all the new results with 
A, Band G in the same direction and to nearly the same extent. 
B 
and G No. 2 were compared, this determination was not con- 
sidered necessary. On October 13th A No. 2 was tested first, 
then B No. 2, then A No. 2 again. This arrangement tended 
to make the result of the comparison independent of any pro 
ressive diminution in the strength of the current operating 
the electromagnet, and it saved much time. On October 27th 
the same method was followed. 
I shall not attempt to give the result of these experiments 10 
absolute measure, but shall write the results obtained on an 
arbitrary scale. : 
Per cent 
Specimen. of Copper. of Zine. Temp. KF, 
A No. 2. 99°9 eg lus oe 100 =m 
B. " 81°08 18°51 21° 1671(— 
6c rd “ “6 4° "8°7 —) 
G. - mas 99°54 oe 158°8(+) 
A No. 2 and B No. 2 were compared at about 25° C., A No. 2 
and G No. 2 at about 19°C. : - 
