/ 
604  Prof.  J.  H.  Jeans  on  the 
is  very  small.  The  curves,  however,  do  not  embody  the 
results  of  a  sufficiently  large  number  of  experiments  ;  so 
that  all  that  can  be  said  is  that,  accepting  the  absorbent 
action  of  the  membrane,  they  are  in  general  agreement  with 
theory.  The  work  must  at  present  be  left  at  this  point,  but 
the  writer  hopes  it  may  be  of  value  in  having  opened  up  an 
interesting  and  profitable  line  for  farther  research  in  the 
theory  of  solution. 
At  present  our  knowledge  of  non-aqueous  solutions  consists 
of  such  various  and  disconnected  data,  so  often  disagreeing 
among  themselves  when  arrived  at  by  different  methods,  that 
further  accumulation  of  experimental  results  is  required 
before  any  generalization  can  be  attempted.  It  has  become 
increasingly  evident  that  the  theories  of  solution  based  on 
work  with  aqueous  solutions  cannot  satisfactorily  cover  the 
data  obtained  where  the  solvent  has  been  other  than  water. 
The  problem  becomes  more  complicated  as  the  influence  of 
the  solvent  is  found  to  be  more  marked.  At  the  same  time 
this  comparatively  recent  development  in  experiment  may  be 
expected  to  afford  a  means  of  making  an  advance  towards 
the  truth  of  the  matter. 
All  we  can  say  now,  Raoult  said  in  summary  in  the  last 
section  of  his  '  Gryoscopie  '  : — i{ ...  the  molecules  of  a  salt 
(in  solution)  can  be  hydrated,  polymerized,  ionized  at  the 
same  time,  in  proportions  varying  with  temperature  and  con- 
centration ;  and,  consequently,  produce  cryoscopic  effects 
(and  among  these  may  be  included  the  parallel  osmotic  ones) 
much  more  complicated  than  is  generally  believed." 
LI.    On  the  Constitution  of  the  Atom. 
To  the  Editors  of  the  Philosophical  Magazine. 
Gentlemen, — 
MAY  I  put  forward  a  suggestion  in  connexion  with  a 
question  discussed  by  Lord  Rayleigh  in  his  paper 
"  On  Electrical  Vibrations  and  the  Constitution  of  the  Atom  " 
(Phil.  Mag.  Jan.  1906)  ? 
Lord  Rayleigh  states  an  objection  against  regarding  the 
atom  as  a  system  in  steady  orbital  motion,  rather  than  as  one 
performing  small  oscillations  about  a  position  of  statical 
equilibrium, — namely,  that  the  sharpness  of  spectral  lines 
indicates  a  definiteness  of  structure  such  as  it  is  difficult  to 
imagine  associated  with  a  system  of  electrons  in  orbital 
motion.     He  goes  on  to  say  :  "  It  is  possible,  however,  that 
