498 Albert P. Mathcivs 



magnet. In the non-magnetic state the magnetism of each 

 molecule is supposed to be neutralized by the surrounding 

 molecules, which have their magnetic axes variously directed. 

 The magnetic field is thus limited to a single molecular diam- 

 eter and will vary with the distance apart of the molecules. 

 The magnetic field of each molecule is delimited by the sur- 

 rounding molecules. If, however, these molecules are 

 oriented, either by acting on each ether, or by external forces, 

 then the magnetic fields coincide and the magnetism may be 

 perceived extending outward from the mass. In other 

 w r ords, to explain why magnetism does not persist in soft iron 

 and to account for magnetic hysteresis, Ewing has made 

 exactly the same assumption which has been made to explain 

 why cohesion does not extend beyond molecular distances. 



It seems to me not impossible that magnetism is the 

 cohesive attraction of a molecule. If the molecule is of such 

 a nature, or shape, that the total effect of the little magnets, 

 its electron couples, coincide more or less completely so that 

 the molecule has a polarity, and the molecules can be oriented 

 in any way and held in position, we have the ferro and para- 

 magnetic substances. If the molecules have many poles, so 

 that there is no polarity of the molecules as a whole, there is a 

 diamagnetic substance. The magnetic field of each molecule 

 would be its cohesive field. 



The recent work of Cotton and Mouton 1 on the orienta- 

 tion of molecules in the magnetic field seems to me to bear out 

 such an interpretation. The work of Weiss 2 and Langevin 3 

 appears to point in the same direction, but Weiss, who has 

 considered the possibility of the identity of cohesion and 

 magnetism, states that he will shortly show that they can not 

 be identical. Nevertheless it appears to me not impossible 

 that magnetism is simply a special case of cohesion, and if 

 this is true the rotation of the plane of polarized light by op- 

 tically active substances would be easily understood. 



1 Cotton and Mouton: Journal de Physique, [5] I, 40 (1911). 



2 Weiss: Journal de Physique, [5] i, 900 (1911); [4] 6, 661 (1907). 



3 Langevin: Ann. Chim. Phys., 5, 70 (1905). 



