ON STRUCTURE OF ATOMS AND THEIR MAGNETIC PROPERTIES. 511 
Nots. 
Prof. P. LanGEvin’s paper on The Structure of Atoms and their 
Magnetic Properties was ordered by the General Committee to be printed 
in extended abstract. This has not been received in time for inclusion, 
and the original abstract is therefore appended :— 
THE STRUCTURE OF ATOMS AND THEIR 
MAGNETIC PROPERTIES. 
By Professor P. LanGeEvin. 
(1) In order to account for magnetic properties it is necessary to 
assume that each atom or molecule possesses in its normal state a quite 
_ definite magnetic moment which is proportional to the total moment of 
_ the quantity of electron movement. This moment can be zero when 
the symmetry of the edifice is sufficient, and always becomes modified 
in the diamagnetic sense under the action of an external magnetic field. 
(2) From the point of view of classical dynamics a system of electri- 
fied particles which participates in thermal agitation cannot exhibit when 
it is isolated, nor assume under the action of an external magnetic field, 
any resultant magnetic moment, and consequently cannot possess any 
_ magnetic property. 
(3) The laws of quanta, on the contrary, allow us immediately to 
predict the existence of molecular magnetic moments which are integral 
multiples of the Bohr magneton, and they alone permit us to develop in 
a completely coherent manner an electronic theory of magnetism in the 
same way-as they have rendered possible a theory of atomic structure 
and of the emission of spectra. 
(4) Magnetic measurements contribute their information regarding 
atomic structure, and atomic models ought to be in quantitative agree- 
ment with them. The family of rare gases seems to give rise to some 
interesting difficulties from this point of view. 
(5) The variation of magnetic properties with the state of chemical 
combination furnishes in like manner important indications and con- 
_firmations of the theory. The progressive disappearance of ferro- and 
para-magnetism when the magnetic atoms (iron, cobalt, platinum, &c.) 
enter into more and more complex combinations shows that chemical 
affinity tends to constitute molecules with no resultant magnetic moment 
—to realise electronic edifices which present a higher and higher 
symmetry. 
1923 XM 
