G8 



HENRY A. ROWLAND 



TABLE VI. 



CAST COBALT, MAGNETIC, AT 230 C. 

 Experiments made February 3, 1874. 



From Table IV we see that at ordinary temperatures cobalt does not 

 offer any exception to the general law for the other magnetic metals 

 that as the magnetization increases, the magnetic permeability first 

 increases and then decreases. We also see that the results satisfy to a 

 considerable degree of accuracy the equation which I have used for the 

 other magnetic metals. The departure from the equation is of exactly 

 the nature that can be accounted for in either of two ways either by 

 the heating of the ring by the current for the higher magnetizing- 

 forces, or by some want of homogeneity in the ring. According to the 

 first explanation, the maximum of magnetization at C. will be some- 

 what lower than the curve indicates; but by the second it must be 

 higher. I, however, incline to the first, that it is due to heating, for 

 two reasons: first, it is sufficient; and secondly, the smaller cobalt ring 

 gives about the same maximum as this. Hence we may take as the 

 provisional value of the maximum of magnetization of cobalt in round 

 numbers 3= 8000, or SB = 100,000. 



We also see from Table IV that, at least in this case, the permeability 

 of cobalt is less than that of nickel, though we could without doubt 

 select specimens of cobalt which should have this quality higher than a 

 given specimen of nickel. The formula at the foot of the Table also 

 shows, by the increased value of the coefficient of K in the right-hand 

 member, that the diameter of the curve is much less inclined to the 

 axis of $ in this case than in the case of nickel or iron. In this re- 

 spect the three metals at present stand in the following order cobalt, 

 nickel, iron. This is the inverse order also of their permeability; but 



