of am Electric Current by Magnetic Action. 125 
_ The values of R. P. given in the first table are in the follow- 
Ing proportion : 
R. C. 
A: No.1, 100 (—) 
| ae 77.6. (—) 
ERR ee 157°5 (+) 
alloys except C, a fall of temperature appears to cause a slight 
increase in the numerical value of of the rotating power. It is 
Possible that upon further trial the apparent exception fur- 
he X periments upon iron and steel were in the main 
te of those already published, but made with more 
e. 
Sort Iron. 
Boek dimensions of the strip of soft iron used in the experi- 
*nts were roughly as follows: 
ee ee ae 
Thickness SE 
P eRe R sw wwe we ee ew ee ee eee 
athe the strip used in 1882* it was obtained through the 
ceeaness of Prof. Langley of the Allegheny Observatory, and 
¢ two strips had probably nearly the same composition and 
character, . 
* This Journal, March, 1883. 
