148 COEEELATION OF PHYSICAL FORCES. 



I have satisfactorily proved, that whenever any metal suscepti- 

 ble of magnetism is magnetised or demagnetised, its tempera- 

 ture is raised. This was shown, first, by subjecting a bar of 

 iron, nickel, or cobalt to the influence of a powerful electro- 

 magnet, which was rapidly magnetised and demagnetised in 

 reverse directions, the electro-magnet itself being kept/ cool by 

 cisterns of water, so that the magnetic metal subjected to the 

 influence of magnetism was raised to a higher temperature 

 than the electro-magnet itself, and could not, therefore, have 

 acquired its increased temperature by conduction or radiation 

 of heat from the electro-magnet ; and secondly, by rotating 

 a permanent steel magnet with its pole opposite to a bar 

 of iron, a thermo-electric pile being placed opposite the 

 latter. 



Dr. Maggi covered a plate of homogeneous soft iron with 

 a thin coating of wax mixed with oil, a tube traversed the 

 centre through which the vapour of boiling water was passed. 

 The plate was made to rest on the poles of an electro-magnet, 

 with card interposed. When the iron is not magnetised, the 

 melted wax assumes a circular form, the tube occupying the 

 centre, but when the electro-magnet is put in action, the curve 

 marking the boundary of the melted substance changes its form 

 and becomes elongated in a direction transverse to the line 

 joining the poles, showing that the conducting power of the 

 iron for heat is changed by magnetisation. 



Thus we get heat produced by magnetism and the conduc- 

 tion of heat altered by it in a direction having a definite rela- 

 tion to the direction of the magnetism. Is it necessary to 

 call in aid ethep or the substance ' caloric' to explain these 

 results ? is it not more rational to regard the calorific effects 

 as changes in the molecular arrangements of the matter sub- 

 jected to magnetism ? 



There is every probability that magnetism, in the dyna- 

 mic state, either when the magnet is in motion, or when the 

 magnetic intensity is varying, will also directly produce chemi- 



