344 



SCIENCE 



[N. S. Vol. LIV. No. 1398 



action of forces whose nature is still un- 

 known." What must be the nature of these 

 forces between elementary magnets? Weiss 

 argues that they are neither magnetic nor 

 electrostatic. These are questions to be left 

 to the reader. 



An attempt to correlate the many researches 

 which have followed in the wake of Curie, 

 Langevin and Weiss leaves the reviewer with 

 a feeling of utter helplessness. The experi- 

 mental work, in many cases, might well serve 

 as examples of the highest type of modern 

 physical research, but, when it comes to the 

 various theories advanced, one must confess 

 to a feeling that it is a good guessing contest 

 in which one is as good as the other. 



Out of Weiss's work, however, has grown 

 a conception that seems destined to have some 

 real meaning as we learn more concerning 

 magnetic phenomena, that is, the magneton. 

 Just as we have found that the electron seems 

 to be the unit out of which we build all 

 other electrical charges so here Weiss finds 

 a similar analogy in that the magnetic mo- 

 ment per gram molecule of various substances 

 seems to be small multiples of a common mag- 

 netic moment, equal to 1,132.5. Since we 

 think of magnetic fields as due to moving 

 charges can the magneton ever be so funda- 

 mental a concept as is the electron? 



C. Seat of Magnetic Powers. — As we go 

 over these various theories one is impressed 

 by the recurrent words, orientation, rotation, 

 revolution, change in magnetic moment, 

 electronic orbits, etc., and then one begins to 

 wonder as to how much magnetic phenomena 

 really depend on these phases of the subject. 



1. When a piece of iron, nickel or cobalt 

 is placed in a magnetic field, what grounds 

 have we for saying that the molecules, atoms 

 or elementary magnets of the specimen are 

 actually turned in situ by the external mag- 

 netic field? Does our affirmation of this 

 question _ rest upon the fact that Ewing^* 

 once on a time pivoted a number of little 

 magnets on needle points and showed how 



14 Ewing, Magn. Indue, in Iron, etc., p. 348 

 et seq., 3d ed. 



they behaved in a magnetic field and said 

 this is the picture of a group of elementary 

 magnets? Small magnets will turn on axes 

 as Ewing showed they would and the logic is 

 that the elementary magnets will also, but 

 note that Ewing would have found hysteresis 

 and B-H curves even if his little model mag- 

 nets had not turned at all. Ewing's magnets 

 did turn and the logic of the argument has 

 tremendous confirmation in the work of 

 Swinburne'-^ who predicted as a consequence 

 of Ewing's theory that if a piece of iron is 

 rotated in a very strong magnetic field and 

 the elementary magnets are held in alignment 

 steadily as the iron cylinder is rotated there 

 will be no changing from one configuration 

 to another which may be unstable and thus 

 dissipate magnetic energy into vibrational 

 energy; consequently there will be a suppres- 

 sion of hysteresis. This was experimentally 

 confirmed. Another verification is found in 

 the experiment of Waggoner and Freeman^^ 

 on the suppression of hysteresis by a longi- 

 tudinal A.C. magnetic field, where the same 

 kind of explanation as Swinburne's might be 

 applied. This suppression of hysteresis seems 

 to be closely associated with a certain degree 

 of freedom to rotate, as for instance Eosen- 

 ham^' points out that when an element whose 

 atomic volume is greater than that of iron 

 with which it is alloyed, the effect of the 

 added element is to decrease the hysteresis. 

 The increased atomic volume, from a me- 

 chanical viewpoint, makes larger interstices 

 between the elementary magnets which per- 

 mits of greater freedom to swing. If we have 

 a theory to explain dia-, para- ferromagnet- 

 ism then that same theory, in order to be a 

 comprehensive magnetic theory, must explain 

 all magnetic phenomena. At this point an 

 outline might be introduced as an aid to keep- 

 ing one's bearing when dealing with general 

 magnetic phenomena. 



15 Swinburne, Baily, Phil. Trails., 187, 715, 1896. 



16 Waggoner and Preeman, Gen'l Elec. Bev., 

 p. 143, Feb., 1918. 



1" Rosenhain, ' ' Introduc. to Phys. Metallurgy, ' ' 

 p. 110, 1915. 



