Magnetic Permeability of various Alloys of Iron. Ita 
the reversal back to softness by increasing the percentage of nickel, was most 
unexpected. Upon putting another set of specimens to mechanical tests for tensile 
strength and resistance to compression, similar changes in the mechanical pro- 
perties were observed at nearly corresponding percentages. The following curves 
illustrate this remarkable behaviour. In fig. 9 the coercive force in C.G.S. units 
of these nickel-steels is plotted, the abscissee being percentages of nickel, and the 
ordinates coercive force x 2. This curve shows the relative magnetic hardness of 
these alloys; the relative magnetic softness is shown by the reciprocals of the 
coercive force, which are also plotted on the same figure. In fig. 10 the 
tensile strength in tons per sq. inch is shown, the abscissz being as in fig. 9, and 
60 : ; : 
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7 
Sara sS : : a \ 
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| 
O AZ| hn f 
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Gq 
~.- Rectproc 
pe ee 5 
~— Coercive force tm C.G.8.units x2 
al of coerctve force X /00 
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s rs 
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to 
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Percentage of Neckel tw alloy. , 
Fie. 9. 
the ordinates the breaking stress in tons per sq. inch. Again in fig. 11 the reduc- 
tion in length per cent. produced by a compression load of 100 tons per sq. inch 
is shown, the ordinates in this case being the percentage reduction.* 
This latter curve illustrates the mechanical softness of these alloys, and will be 
seen to be very similar to that of the magnetic softness on fig. 9, whereas the curve 
on fig. 10, showing the tenacity, resembles the magnetic hardness shown on fig. 9. 
* See paper on Wickel Steels, by R. A. Hadfield, Proc. Institute of Civil Engineers, March, 1899. 
