•418  Notices  respecting  New  Books. 
it  will  be  at  once  noticed,  furnishes  a  means  of  calculating 
the  molecular  conductivities  of  (1)  insoluble  or  unstable 
bases,  and  (2)  insoluble  or  unstable  salts,  the  molecular 
conductivities  of  which  cannot  be  determined  by  direct 
measurement. 
Similarly,  it  can  be  shown  that 
=/aVm1x2—  )^m2x2 
Hence  fiVMxx  — fii'x2x~  fJLVx.^— pvn^ 
=  /^WMlX2—  /^m2X2 
=  ^^M1X3  — ^M2X3 
constant. 
This  final  equation,  it  will  be  observed,  is  identical  with 
the  hitherto  unexplained  fact  discoA'ered  by  Kohlrausch  (and 
further  extended  by  Ostwald,  see  Lehrb.  tier  Ahj.  Chemie,  ii.). 
East  London  Technical  College, 
London,  E. 
XXXVI.  Notices  respecting  New  Books. 
Ions,  Electrons,  Corpusculcs.  Meinoires  reunis  et  public's  par 
H.  Abeaham  et  P.  La.ngevin\  Paris  :  Grauthier-Villars. 
1905.  Premier  Fascicule,  pp.  xvi  +  512.  Second  Eascicule, 
pp.  513-1138. 
TE  any  proof  were  needed  of  the  extent  to  which  the  modern 
-*-  theory  of  electrons  dominates  physical  science,  it  might,  not 
inappropriately,  be  regarded  as  furnished  by  the  publication  of 
the  two  large  volumes  under  review.  The  Societe  Erancaise  de 
Physique,  which  has  already  done  good  work  in  rendering- 
accessible  to  numerous  readers  collections  of  important  memoirs 
on  various  branches  of  physics  (issued  under  the  title  of  Collection 
de  Memoires  sur  la  Physique),  has  performed  another  most  useful 
service  by  collecting  all  the  scattered  papers  dealing  with  the  rise 
and  development  of  the  electronic  idea,  and  arranging  them  in  a 
form  which  renders  it  an  easy  matter  to  look  up  the  particular 
contributions  towards  any  branch  of  the  subject  made  by  different 
investigators.  . 
Originally,  the  work   was   to   have    been    edited    by   the    late 
M.  Alfred  Potier  (to  whose  memory  it  is  dedicated),  but  owing  to 
