220 



PROCEEDINGS OF THE AJIERICAN ACADEMY. 



that for the rod of same diameter worked out beginning on October 9. 

 It will be noticed that these values for iV are considerably larger than 

 those of the earlier series. This again shows very clearly the difference 

 between the reversal and the step method. 



TABLE VIII. [Figure 11.] 



November 16, 1906. 



Diam. = 0.3175 cm. = 1/8 in. 



Reversals. 



Figure 13 gives the experimental curves corresponding to Table XI, 

 January 18, 1907. They were taken by the step method, and each 

 curve was based on three or four separate magnetizations from zero to the 

 highest value of H', so that good average results might be obtained. 

 It will be noticed that the curve for m — 200 passes very nearly 

 through two sets of observations, but that on either side of it lie 



