470 



PROCEEDINGS OF THE AMERICAN ACADliJMY 



TABLE XI. 



Cobalt magnetic. 



-Dec. 27, 1884. 

 —5° C. Softened. 



TABLE XII. — April 30, 1884. 

 Cobalt maffnetic. 20° C. Hardened. 



All the iron rings were forged. The cobalt ring was cast. 



Four of the iron rings were made from the same bar of Norway 

 iron, and were of nearly the same size. Nos. 1 and 2 are two of them. 

 The third was cooled down to —25° C. or — 40° C. by means of lique- 

 fied nitrous oxide, and a partial curve taken. The fourth was heated 

 up to 280° C. in liquid parafTine, and a few measurements taken. 

 Altliough complete curves were not obtained at either of these tempera- 

 tures, the part obtained differed but slightly from the corresponding 

 parts of the curves of Nos. 1 and 2. 



In order to prevent the insulation from being destroyed at the high 

 temperature, the ring was completely covered, except in three places. 



