4 ASHWORTH, Intrinsic Field of a Magnet. 



Treating the intrinsic field within the iron as the unknown 

 quantity its magnitude can then be calculated, and the 

 result is found to be of the order of the intrinsic field 

 required by the ferro-magnetic equation analogous to Van 

 der Waals' equation, or as required by Prof P. Weiss in 

 his investigations.® 



Although the experiment is thus in favour of an in- 

 trinsic field of some millions of gausses, the derivation of 

 this enormous field is still unexplained, and its magnitude 

 needs further confirmation. 



There are other experimental results which might be 

 brought to bear on the question. For example, there is 

 a remarkable and rapid change in the thermo-electro- 

 motive force of both iron and nickel at or about the critical 

 temperature of these metals. Also the temperature co- 

 efficient of electrical resistance of iron and nickel is 

 abnormally large compared to other pure metals. These 

 facts are probably connected with the magnetic qualities 

 of iron and nickel, and, if so, should give some clue to the 

 magnitude of the intrinsic field when submitted to quanti- 

 tative investigation. 



Sir J. A. Ewing's Presidental address to Section G at 

 the British Association Meeting at York in 1906, on the 

 similarity of crystalline polar forces to molecular magnetic 

 forces, is suggestive in connection with these newer views 

 of a very large intrinsic field in a magnet. 



" Vide Appendix. 



