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JULY 18i'5. "^JSHKO*.?^ 



I. On the Magnetic B.elation^'^^pqid^i'Qharacters of the Metals, 

 By Michael Faraday, D.C.L.^ F.B.S.t Foi-eign Asso- 

 ciate of the Acad. Sciences^ 'Si'C.'^^^ ivyni^ll .i\A U, -. ijiMt^i.iil A 



IN two former communications to iRe.E^iiosppnicaflitaga-j, 

 zinet I'especting- the magnetic characters of metals ge- 

 nerally and the temperatures at which they respectively lost ; 

 or gained the powers of magnetic induction, I said that iron, 

 and nickel were the only metals which had this powers and . 

 that I could not find it in pure cobalt. In this 1 was in error; 

 cobalt has this property in common with iron and nickel, as 

 others have said. I have sought for the piece of cobalt on 

 which I experimented and believed to be pure, but cannot 

 find it, and am now unable to ascertain the cause of my error, 

 though not too late to correct it. 



By favour of Dr. Percy and Mr. Askin I have recently 

 experimented with two fine pieces of pure cobalt prepared b^^ 

 the latter, both being well-fused and perfectly clean nlasse^f^. 

 This metal becomes strongly magnetic by induction, either of - 

 a magnet or an electro-current, and can easily be made to lift 

 more than its own weight. Like soft iron and nickel, it does 

 not retain its magnetism when the inducing influence is re- 

 moved. ' r ■'/ 



It was to me a point of great interest to ascertain whether, 

 and at what temperature, cobalt would lose this powej^ ,^nd . 

 become as the unmagnetic metals. To my surprise I found 

 this to be very high, not merely much higher than with nickel, 

 but far above that required for iron or steel, and nearly ap- 

 proaching the temperature of melted copper. That for iron 

 is a moderate red heat, and that for nickel the temperature 

 of boiling oil only. As the temperature rises, the magnetic 

 force of the cobalt continues, apparently undiminished, to 

 * Communicated by the Author, 

 t 1836, vol. viii. p. 177, and 1839, vol. xiv. p. 161. 

 Phil. Mag. S. 3. Vol. 27. No. 177. My 1845. B 



