2 Prof. Faraday on the Magnetic Relations of Metals. 



a certain degree of heat, and then suddenly ceases ; and it 

 comes on as suddenly in descending from still higher tempe- 

 ratures. 



The oxide of cobalt procured by burning the metal cobalt 

 on charcoal by a jet of oxygen was obtained as a fused glo- 

 bule and was not magnetic. 



The oxide of nickel being heated and cooled is not mag- 

 netic, but whilst heating care must be taken that it is not re- 

 duced. If heated in the flame of a spirit-lamp, especially at 

 the lower part, it will often appear to be not magnetic, and 

 then as the temperature falls will become magnetic ; but this 

 is caused by the reduction of a little of the oxide at the edges 

 or elsewhere in the mass to the metallic state, and its exhibi- 

 tion of the properties of the metal at temperatures above and 

 below the magnetic point. 



Manganese. — A piece of manganese prepared by Mr. 

 Thomson and considered pure was put into my hands. It 

 contained a trace of iron ; it was very slightly magnetic, and 

 probably only in consequence of the little iron present. Before 

 a jet of oxygen or charcoal, it burnt with sparkles somewhat 

 in the manner of iron, and produced an oxide which could be 

 obtained either as a porous white mass or as a dense compact 

 brown mass, translucent in small slices; but in neither state 

 was the oxide magnetic. 



I then cooled* manganese, chromium and many other 

 metals and bodies to the lowest temperature which I could 

 obtain by a mixture of aether and solid carbonic acid placed 

 i7i vacuo-\, the temperature being then not higher than 156° F. 

 below 0°, but not one of them assumed the magnetic state. 

 The following is a list of the substances: — 



Platinum. 



Gold. 



Silver. 



Palladium. 



Copper. 



Tin. 



Lead. 



Cadmium. 



Zinc. 



Rhodium. 



Manganese. 



Chromium. 



Titanium. 



Iridium and Osmium. 

 Antimony. 

 Arsenic. 

 Bismuth. 

 Fusible metal. 

 Speculum metal. 

 Plumbago. 

 Gas- retort carbon. 

 Kish. 

 Orpiment. 

 Realgar. 



Sulphuret of antimony, 

 bismuth. 



* Phil. Mag., 1839. vol. xiv. p. 162. 



f Fhilosopbical Transactions, 1845, pp. 157, 158. 



