690 Prof. J. J. Thomson on the Magnetic Properties of 



the particks describing free orbits these tendencies balance 

 each other. 



15^ With a system of particles whose energy is being 

 dissipated in the way described in § 13 we should get mag- 

 netic properties, these properties would be properties in- 

 herent in the atom, and would not explain the magnetic 

 properties of iron for example, where the magnetization is j-o 

 much affected by gross mechanical strain as to indicate that 

 it depends largely if not entirely on the properties possessed 

 by aggregations of large numbers of molecules. In the case 

 ot such aggregations, however, we may easily conceive that 

 the orbits of charged bodies moving within them may not be 

 free, but that in consequence of the forces exerted by the 

 molecules in the aggregate, the orbit may be constrained to 

 occupy an invariable position with respect to the aggregate 

 - — as if, to take a rough analogy, the orbit was a tube bored 

 through the aggregate, so that the orbit and aggregate move 

 like a rigid body, and in order to deflect the orbit it is 

 necessary to deflect the aggregate. Under these conditions 

 it is easy to see that the orbits would experience forces equi- 

 valent on the average to those acting on a continuous current 

 flowing round the orbit; the aggregate and its orbit would 

 under these forces act like a system of little magnets ; and 

 the body would exhibit magnetic properties quite analogous 

 to those possessed by a system of Amperean circuits. 



1 G. On the effect of a magnetic field on the frequency ot the 

 vibrations emitted by a system of n corpuscles rotating in a 

 circular orbit. 



The results obtained on pages (679) and (680) give the 

 solution of this problem. We shall for the sake of breA'ity 

 confine our attention (1) to the vibrations emitted along the 

 axis of .?, which is parallel to the magnetic force; for points 

 along this axis ?/— ~ = 0; and (2) to the vibrations emitted in 

 a direction at right-angles to the magnetic force, say along 

 the axis of ?/, so that ,r = 0, r = 0. 



The components of the magnetic force are expressed by 

 terms of the form 



dx^ dy^ dz" ~T 



(1) 



When the distance from the vibrating system is a large 

 number of wave-lengths, the most important term in the 

 expression (1) is proportional to 1/V, and this term can be 

 got by wilting 



