358 Molecular Theory of Induced Magnetism. [June 19 



(1.) That in considering the magnetisation of iron and other mag- 

 netic metals to be caused by the turning of permanent molecular 

 magnets, we may look simply to the magnetic forces which the 

 molecular magnets exert on one another as the cause of their direc- 

 tional stability. There is no need to suppose the existence of any 

 quasi- elastic directing force or of any quasi-frictional resistance to 

 rotation. 



(2.) That the intermolecular magnetic forces are sufficient to 

 account for all the general characteristics of the process of mag- 

 netisation, including the variations of susceptibility which occur as 

 the magnetising force is increased. 



(3.) That the intermolecular magnetic forces are equally compe- 

 tent to account for the known facts of retentiveness and coercive 

 force and the characteristics of cyclic magnetic processes. 



(4.) That magnetic hysteresis and the dissipation of energy 

 which hysteresis involves are due to molecular instability resulting 

 from intermolecular magnetic actions, and are not due to anything in 

 the nature of frictional resistance to the rotation of the molecular 

 magnets. 



(5.) That this theory is wide enough to admit explanation of the 

 differences in magnetic quality which are shown by different sub- 

 stances or by the same substance in different states. 



(6.) That it accounts in a general way for the known effects of 

 vibration, of temperature, and of stress upon magnetic quality. 



(7.) That in particular it accounts for the known fact that there is 

 hysteresis in the relation of magnetism to stress. 



(S.) That it further explains why there is, in magnetic metals, hyste- 

 resis in physical quality generally with respect to stress, apart from 

 the existence of magnetisation. 



(9.) That, in consequence, any (not very small) cycle, of stress 

 occurring in a magnetic metal involves dissipation of energy. 



XIV. " On the Relation between the Magnetic Permeability of 

 Rocks and Regional Magnetic Disturbances." By A. W. 

 ROCKER, M.A., F.R.S. Received May 30, 1890. 



[Publication deferred.] 



XV. " On the Causes of the Phenomena of Terrestrial Mag- 

 netism, and on some Electro-mechanism for exhibiting the 

 Secular Changes in its Horizontal and Vertical Com- 

 ponents." By H. WILDE, F.R.S. Received April 22, 1890. 



[Publication deferred.] 



