CONTEMPORARY ADVANCES IN PHYSICS 245 



that of all their magnetic moments, are zero. Now suppose that a 

 field is suddenly applied, parallel to the axis of the cylinder. The 

 substance is suddenly magnetized; this signifies that the resultant 

 of the magnetic moments, and hence that of the angular momenta, 

 are no longer zero. Let / stand (as heretofore) for the former re- 

 sultant, and P for the latter. Now it is desirable to remember that 

 each atom consists of a nucleus and an electron-family; that the 



ERRATA: Contemporary Advances in Physics, XXX — The The- 

 ory OF Magnetism — Karl K. Darrow 



I Bell System Technical Journal, April, 1936 



Page 245: Last sentence, " Its lowest possible value (from theorv) is 

 e/2uic, in which c, in, and c have their usual meanings;" 



should read 



V 



" One pre-eminent value (from theory) is c/2nic, in which 

 e, m, and c have their usual meanings ; " 



Page 246 : First sentence, '* Its highest possible value is twice as 

 great ; " 



should read 



" Another pre-eminent value is twice as great ; " 



llliD A (JH.1KJ 



is a rare sort of thing: it is a quantity of which the numerical value, 

 measured on pieces of bulk matter, is appropriate also to the elemen- 

 tary particles. If the substance is made up of identical elementary 

 magnets of magnetic moment m and angular momentum p, then I/P 

 is fx/p. Since /z and p are knowable from spectra, so also is their ratio. 

 Its lowest possible value (from theory) is e/lmc, in which e, m, and c 

 have their usual meanings;^ this would always occur if the electrons 

 had no spins; actually it occurs if the electron-family of the atom is so 



* Most nuclei possess magnetic moments, which, however, are so excessively small 

 that they can be detected only by experiments of extreme delicacy. 



* Charge (in E.S.U.) and mass of the electron, and speed of light in vacuo. For the 

 theory underlying these statements, c.f. I.e. pp. 285-300. Often the ratio of the 

 experimental value of nip to the quantity ejltnc is called an "experimental g-value," 

 the ratio of the theoretical value to elZmc being conventionally denoted by g. 



