﻿830 
  Notices 
  respecting 
  New 
  Books. 
  

  

  chlorides, 
  its 
  combination 
  with 
  chlorine 
  is 
  a 
  protochloride 
  

   and 
  its 
  formula 
  RaOl. 
  

  

  The 
  atomic 
  weight 
  226 
  shown 
  for 
  radium 
  will, 
  therefore, 
  

   require 
  to 
  be 
  reduced 
  by 
  35 
  (the 
  equivalent 
  of 
  chlorine), 
  or 
  

   226-35 
  — 
  191. 
  Although 
  this 
  value 
  is 
  still 
  7 
  units 
  higher 
  

   than 
  the 
  value 
  shown 
  in 
  my 
  table, 
  yet, 
  considering 
  the 
  dif- 
  

   ficulties 
  attending 
  the 
  experiments 
  on 
  account 
  of 
  the 
  minute 
  

   quantities 
  of 
  the 
  chloride 
  operated 
  upon, 
  the 
  result 
  is 
  as 
  near 
  

   the 
  theoretical 
  value 
  as 
  might 
  reasonably 
  be 
  expected. 
  

  

  While 
  extreme 
  care 
  has 
  been 
  taken 
  in 
  both 
  these 
  deter- 
  

   minations 
  to 
  eliminate 
  barium 
  from 
  the 
  mineral 
  experimented 
  

   with, 
  which 
  element 
  would 
  reduce 
  the 
  value 
  shown 
  for 
  radium 
  

   on 
  account 
  of 
  its 
  lower 
  atomic 
  weight 
  (137), 
  no 
  mention 
  is 
  

   made 
  or 
  indication 
  given 
  by 
  Dr. 
  Thorpe 
  of 
  any 
  residual 
  

   quantity 
  of 
  uranium 
  that 
  might 
  have 
  remained 
  in 
  the 
  radium 
  

   chloride 
  from 
  which 
  the 
  atomic 
  weight 
  was 
  determined. 
  

   His 
  investigation 
  commenced 
  on 
  about 
  half 
  a 
  ton 
  of 
  pitch- 
  

   blende 
  (uranium 
  oxide) 
  residues. 
  It 
  would 
  have 
  been 
  in- 
  

   teresting 
  to 
  know 
  the 
  steps 
  by 
  which 
  this 
  large 
  amount 
  of 
  

   uranium 
  oxide 
  residues 
  was 
  reduced 
  to 
  a 
  single 
  grain 
  of 
  

   radium 
  chloride. 
  

  

  As 
  the 
  atomic 
  weight 
  of 
  uranium 
  is 
  240, 
  the 
  elimination 
  

   of 
  two 
  and 
  a 
  half 
  per 
  cent, 
  of 
  uranium 
  chloride 
  from 
  the 
  

   grain 
  of 
  radium 
  chloride 
  ultimately 
  obtained 
  would 
  reduce 
  

   the 
  atomic 
  value 
  191 
  to 
  184, 
  the 
  atomic 
  weight 
  of 
  radium 
  as 
  

   shown 
  in 
  my 
  tables. 
  

  

  Yours 
  faithfully, 
  

  

  H. 
  Wilde. 
  

   Alderley 
  Edge, 
  Sept. 
  29th, 
  1908. 
  

  

  LXXI. 
  Notices 
  respecting 
  Neiv 
  Books. 
  

  

  The 
  Mathematical 
  Theory 
  of 
  Electricity 
  and 
  Magnetism. 
  By 
  J. 
  H. 
  

   Jeaxs, 
  M.A., 
  E.R.S. 
  Pp. 
  viii 
  + 
  536. 
  Cambridge 
  University 
  

   Press, 
  1908. 
  

  

  rpHIS 
  treatise 
  is 
  intended 
  to 
  give 
  the 
  mathematical 
  theory 
  of 
  the 
  

   •-*- 
  fairly 
  well-defined 
  range 
  in 
  Electromagnetic 
  Theory 
  which 
  every 
  

   student 
  of 
  physics 
  may 
  be 
  expected 
  to 
  have 
  covered, 
  with 
  more 
  or 
  

   less 
  thoroughness, 
  before 
  proceeding 
  to 
  the 
  study 
  of 
  special 
  branches 
  

   or 
  developments 
  of 
  the 
  subject. 
  The 
  treatment 
  is 
  considerably 
  

   more 
  elementary 
  than 
  that 
  in 
  Maxwell's 
  Treatise 
  upon 
  which 
  it 
  is 
  

   based. 
  It 
  also 
  includes 
  much 
  detail 
  which 
  is 
  not 
  in 
  Maxwell. 
  

   xA-lthough 
  the 
  author 
  makes 
  no 
  claim 
  for 
  much 
  newness 
  or 
  

   originality 
  of 
  treatment, 
  and 
  even 
  expressly 
  disclaims 
  having 
  

   taken 
  much 
  interest 
  in 
  the 
  writing 
  of 
  it(!), 
  yet 
  we 
  think 
  that 
  the 
  

   -result 
  is 
  to 
  be 
  highly 
  commended. 
  Undoubtedly 
  it 
  appears 
  to 
  us 
  

  

  