392 Intelligence and Miscellaneous Articles. 



not necessarily of all such motions, but of those among them 

 which are capable of restoring energy to the parts of the 

 molecule carrying electra (see Stoney on " Double Lines in 

 Spectra/ - ' Scientific Transactions of the Royal Dublin Society, 

 vol. iv. part xi.) whenever the motion of the electron has 

 transferred energy from the molecule to the sether. As ful- 

 filling this criterion we are probably to include all irrotational 

 motions within the molecules, and we must also include rela- 

 tive motions of the molecules — all of them indeed if time 

 enough be allowed for turmoil within a fluid to subside. It 

 does not include any motion which the molecules have in 

 common, as in wind, or in the rotation of a wheel. 



When these circumstances are taken into account, it is 

 obvious that the energy of the heat-motions of an individual 

 molecule undergoes rapid fluctuations, while there may be a 

 definite average of the energy of these motions, whether esti- 

 mated by what happens in an individual molecule over a 

 sufficiently long period of time, or when estimated by what 

 occurs simultaneously in all the molecules of a body. In 

 other words, the motions of an individual molecule do not 

 from instant to instant conform to the Second Law of Thermo- 

 dynamics, although the law may apply both to the average of 

 the motions of a single molecule taken over a long period of 

 time, and to the average of the simultaneous motions of vast 

 multitudes of associated molecules. As regards molecular 

 motions (the motions within a solid, or motions within a fluid 

 that do not produce currents in the fluid), the millionth of 

 one second is a long period. 



XXXVIII. Intelligence and Miscellaneous Articles. 



ON THE MAGNETIZATION OF IRON RINGS SLIT IN A RADIAL 

 DIRECTION. BY H. LEHMANN. 



THE chief results of the present research may be summed up in 

 the following principles, which hold for an imperfectly closed 

 ferromagnetic ring, the radius of which is large in comparison 

 with the radius of the section : — 



1. The demagnetizing factor, or the factor which, multiplied 

 by the mean magnetization, gives the mean factor of the demag- 

 netizing force, is constant up to about half the saturation. 



2. The coefficient of dispersion (Streuangs-coefficient), the ratio 

 of the mean induction to that in the slit, is constant up to half 

 saturation. 



3. The region of the dispersion of the lines of force is limited 

 essentially to the vicinity of the slit, and is narrower as the 

 magnetization increases. 



4. The coefficient of dispersion is independent of the radius of 

 the ring ; in regard to its constancy (2), it only depends on the 



