120 PROCEEDINGS OF THE AMERICAN ACADEMY 



The analyses of the cobalt and nickel were as follows : — 



Nickel 1. 3.1328 grammes gave 0.0115 gramme Fe 2 3 . 



0.0115 gramme Fe 2 O s = .00805- Fe = 0.256 %. 



Nickel 2. 4.3002 grammes gave 0.0178 gramme Fe 2 3 . 



0.0178 gramme Fe 2 3 = 0.01246 Fe = 0.289 %. 



Cobalt 1. 4.2264 grammes gave 0.0492 gramme Fe 2 3 . 



0.0492 gramme Fe 2 3 = 0.03444 gramme Fe 2 = 0.814 %. 



Cobalt 2. 4.5606 grammes gave 0.0358 gramme Fe 2 3 . 



0.0358 gramme Fe 2 8 = 0.02506 gramme Fe = 0.55 %. 



Cobalt 3. 3.3940 grammes gave 0.1091 gramme Ni 0. 



0.1091 gramme Ni O = 0.08571 gramme Ni = 2.52 %. 



The weight of bar of cobalt was 1 63 grammes approximate. 

 „ „ nickel „ 159 grammes approximate. 



The bars of nickel, cobalt, iron, and steel, all emitted loud musi- 

 cal notes while in the process of being maguetized and demagnetized, 

 the note emitted by the iron being the loudest. These notes could 

 easily be heard two hundred feet away from the bars. 



Among the papers published on the magnetic metals is one by 

 Professor Barrett of the Royal Cullege of Science, Dublin, which is 

 entitled " The Molecular Changes that accompany the Magnetization 

 of Iron, Nickel, and Cobalt." After giving a resume of what has 

 been written on this subject, the author remarks : " Nickel is invaria- 

 bly ranked above cobalt in the scale of magnetic metals, Faraday and 

 others placing it next to soft iron. But the bar of nickel I have used, 

 when submitted to the same magnetizing current as the cobalt bar, 

 exhibits far less portative force than the cobalt. It is remarkable that 

 the iron impurity contained in the cobalt is able to produce so power- 

 ful an influence. The nickel, like other specimens I have met with, 

 has a very slight retentive power when magnetized ; whereas, the cobalt 

 has a high degree of coercive force." 



It appears from our result that it is not the iron in the cobalt 

 which produces the high amount of molecular heating noticed by us ; 

 for the chemical analyses showed an amount of iron which would be 

 inappreciable in the electrodynamic experiments. 



The following table, for which we are indebted to a paper by Pro- 

 fessor W. F. Barrett, published in the London " Philosophical Maga- 

 zine," 1873, Vol. XLVI. page 478, exhibits the relationship of the 

 magnetic metals : — 



