A. 8. Kimball—Magnetic Strains in Iron. 99 
Art. XVL—WMagnetic Strains in Iron; by A. 8S. KIMBALL, 
Professor of Physics in the Worcester Free Institute of 
Industrial Science. 
‘Tue object of this paper is to describe certain experiments 
made by inducing a magnetic state in bars of soft iron sub- 
jected to varying degrees of mechanical stress. As the result, 
we always have changes either in the form or dimensions of the 
bar, similar to those produced by the mechanical stress previ- 
ously applied, and therefore the term magnetic strain does not 
4,000 pounds ; and on the removal of the small weight, the beam 
promptly returned to its normal position, The course o 
experiment was as follows: Several pieces of the same kind of 
iron, made as nearly as possible uniform in size, were broken in 
the machine. The alternate ones, in the order in which they 
were cut from the bar, were magnetized to saturation by a 
helix, through which a constant current was passing during the 
experiment. The heating effects of the helix were slight, and 
probably without influence. The tabulated results were then 
compared, and from thern the following conclusion was reached : 
A soft iron bar has its tenacity increased about nine-tenths of one 
per cen magnetizing it to saturation. The following table 
gives the results obtained by breaking a series of pieces of 
