MAGNETIC ALLOYS OF IRON, NICKEL, AND COBALT 441 



you see on topographical maps and represent the intersections with 

 the surface of planes parallel to the base at definite elevations. Each 

 line locates the compositions of those alloys which have equal values of 

 initial permeability. 



In this solid diagram of the initial permeabilities for the alloys in 

 annealed conditions, there are three regions of composition which are 



Fig. 3 — Initial permeabilities for annealed alloys. 



of special interest. The first of these is in the binary iron-nickel 

 series represented by the back face of the diagram, which may be 

 referred to as the nickel-iron plane. The nickel percentage is indicated 

 by the numbers at the intersections of the permeability coordinates 

 with the surface. The left-hand corner represents 100 per cent iron 

 and the right-hand corner 100 per cent nickel, with initial permeabilities 

 of 250 and 200, respectively. Between these limits of composition 



