122 E. H. Hall—Rotation of the Equipotential Lines 
Bre gNoi %) 
Length of main strip when weighed ------.-- 3°70 cm, 
Width of main strip when weighed ....-.-.-- 1°06 cm. 
Area of whole strip when weighed -__-.----- 4°28 cm. sq. 
— CJte Mel whe eee enews sie sueonce 2915 grm, 
TNORINE oe e ee ao a oa ee Ee : 
Average thickness from the data ----_.-.-.--- 00934 cm. 
By calipers thickness at one end, ‘0098; at other end, °0100; 
between arms, ‘0100; average, 00993 cm. Take for true thick- 
ness nee ween arms 00941 cm. Distance between strips B, 5, 
about re 
G. (No. 1.) 
Length of main strip when weighed.......-.. 4°17 cm. 
Width of main strip when weighed ---__--.-- 109 cm. 
Area of whole strip when weighed -.-..--.-- 5°03 cm. 8q. 
Hae sii a: woh mayen Rte ea 5 ae ee edi "1206 grm. 
DIODES oxic 6 ip neues ok bee Oh Sens : 
Average thickness from these data _.....--.. ‘00333 om. 
From a somewhat careful use of the calipers it appeared that 
the thickness between ti arms was about 44 per cent greater 
than the average thickne 
Take then for thicknéad Rene arms *00348 cm. Distance 
between strips B, B, about 3 
e main object in the experiments upon these metals and 
their alloys was to determine whether the alloys would range 
themselves according to any simple law so that the magnitude 
of the rotational power in any alloy might be inferred from its 
known pel hg of copper and zinc. Some ere fe was 
cases except the experiments of Aug. 11th on copper. On 
that day the current used was less than one half as strong as 
that used later. “The same strip of copper was tested again 
Aug. 29th with a current of the usual strength and the agree- 
ment between the ay obtained under so widely different 
conditions is quite ¢ 
In the following table and throughout this article the C. G. 
S. system is used wherever no statement is made to the con- 
trary. The Bisco. symbols used with the tables need 
explanation 
