A. S. Kimball—Magnetic Strains in Iron. 101 
amount, occur in a bar which is neither compressed nor 
stretched. 4th. If the bar be subjected to tension, the elonga- 
subsequent passage of the same current, and that the sec- 
ond, third and all subsequent elongations of the bar by a 
constant magnetizing force, are equal to each other; also that 
which have been shortened by compression, will be elongated 
by the action of the magnetizing force, while the fibers of the 
bar on the convex side, which have been subjected to tensional 
strain, will either be elongated by a less amount or will be 
shortened. As the result of this action we may be tolerably 
n 
soos side, was placed upon the platform of a Fairbanks 
scale. el 
closed in its helix, was adjusted upon its supports so that the 
oa of the micrometer screw was just below its middle. The 
elix was made in two parts for convenience in loading the 
bar. The middle of the bar supported one corner of a trian- 
gular platform, whose sides were four, eight and nine feet. 
The other corners of this platform were supported upon points. 
the adjustment of the bar.. The micrometer screw had sixty 
threads to the inch, and its head was gra uated to three hun- 
ed parts. The unit of measurement is therefore rstov of an 
inch. At first, contacts of the screw with the bar was deter- 
* This Journal, August, 1873. 
