SHUDDEMAGEN. — DEMAGNETIZING FACTORS FOR IRON RODS. 195 



larger. We may then plot out the abscissa-differences between this 

 normal curve and all the others, and thus actually construct the N- 

 curves. 



The only experimental magnetization curves for a number of varying 

 m's which had been published before 1895 are those obtained by 



FlGCKE 2. 



Ewing's magnetization curves for a soft iron wire of diameter 0.158 cm. 



Ewing 12 for m = 50, 75, 100, 150, 200, and 300 (see Figure 2), and 

 some by Tanakadate" for rather small values of m, his highest being 

 about m = 39. Ewing's iron cylinder was a wire of diameter = 0.158 

 cm. and original length = 47.5 cms., the other m's being obtained by 

 cutting off pieces from each end. The maximum permeability for this 

 iron was found to be yu, = 3500. Tanakadate's iron wires were of 



12 Phil. Trans., 176, II, 535 (1885). 



