﻿Chemistry 
  and 
  Physics. 
  303 
  

  

  excited 
  by 
  A3303 
  but 
  also 
  the 
  D 
  lines, 
  at 
  A5893. 
  This 
  observa- 
  

   tion 
  is 
  very 
  important 
  because 
  it 
  clearly 
  establishes 
  the 
  existence 
  

   of 
  some 
  mechanical 
  coupling 
  between 
  the 
  system 
  which 
  absorbs 
  

   A3303 
  and 
  that 
  which 
  emits 
  A5893. 
  Furthermore 
  this 
  phe- 
  

   nomenon 
  seems 
  to 
  have 
  no 
  analogy 
  in 
  the 
  behavior 
  of 
  the 
  vibra- 
  

   ting 
  systems 
  dealt 
  with 
  in 
  classical 
  mechanics. 
  On 
  the 
  other 
  

   hand, 
  the 
  radiations 
  of 
  higher 
  frequency 
  at 
  A3303 
  were 
  not 
  

   detected 
  when 
  the 
  radiations 
  of 
  lower 
  frequency 
  at 
  A5893 
  were 
  

   caused 
  to 
  pass 
  through 
  the 
  vapor 
  in 
  the 
  resonance 
  bulb. 
  The 
  

   lines 
  of 
  the 
  subordinate 
  series 
  gave 
  no 
  re-emission. 
  

  

  When 
  D 
  light 
  falls 
  on 
  sodium 
  vapor 
  of 
  appropriate 
  density, 
  

   it 
  is 
  known 
  that 
  an 
  intense 
  surface 
  emission 
  occurs 
  from 
  the 
  

   front 
  layer, 
  and 
  a 
  weak 
  one 
  from 
  succeeding 
  layers. 
  Analysis 
  

   by 
  absorption 
  in 
  an 
  independent 
  layer 
  of 
  sodium 
  vapor 
  showed 
  

   that 
  the 
  superficial 
  emission 
  is 
  more 
  absorbable, 
  and 
  therefore 
  

   nearer 
  the 
  center 
  of 
  the 
  I) 
  lines, 
  

  

  Polarization 
  could 
  not 
  be 
  detected 
  in 
  the 
  ultra-violet 
  resonance 
  

   radiation, 
  though 
  in 
  accordance 
  with 
  previous 
  observers 
  it 
  was 
  

   readily 
  perceived 
  in 
  D 
  resonance. 
  — 
  Proc. 
  Roy. 
  Soc, 
  96A, 
  272, 
  

   1919. 
  h. 
  s. 
  u. 
  

  

  9. 
  Electric 
  Oscillations 
  and 
  Electric 
  Waves; 
  by 
  George 
  W. 
  

   Pierce. 
  Pp. 
  ix, 
  517, 
  136 
  figures. 
  New 
  York, 
  1920 
  (McGraw- 
  

   Hill 
  Book 
  Co.). 
  — 
  This 
  book 
  is 
  designed 
  to 
  present 
  a 
  mathemat- 
  

   ical 
  treatment 
  of 
  some 
  of 
  the 
  fundamentals 
  of 
  the 
  theory 
  of 
  

   electric 
  oscillations 
  and 
  electric 
  waves. 
  The 
  material 
  is 
  conve- 
  

   niently 
  divided 
  into 
  two 
  Books, 
  of 
  which 
  the 
  first 
  (17 
  chapters, 
  

   345 
  pages) 
  relates 
  to 
  electric 
  oscillations 
  and 
  the 
  second 
  (9 
  

   chapters) 
  to 
  electric 
  waves. 
  Book 
  I 
  deals 
  with 
  circuits 
  contain- 
  

   ing 
  capacity, 
  resistance, 
  and 
  self-inductance, 
  with 
  the 
  free 
  

   oscillations 
  of 
  variously 
  coupled 
  circuits, 
  with 
  resonance 
  rela- 
  

   tions, 
  etc. 
  Book 
  II 
  is 
  devoted 
  to 
  Maxwell's 
  equations, 
  to 
  wave 
  

   equations, 
  to 
  electrical 
  doublets, 
  and 
  to 
  theoretical 
  investigations 
  

   of 
  the 
  radiation 
  characteristics 
  of 
  an 
  antenna. 
  The 
  author 
  says 
  : 
  

   "Although 
  the 
  selection 
  of 
  material 
  particularly 
  applicable 
  to 
  

   radiotelegraphy 
  has 
  been 
  the 
  first 
  consideration, 
  yet, 
  because 
  the 
  

   electromagnetic 
  theory, 
  which 
  is 
  fundamental 
  to 
  radiotelegra- 
  

   phy, 
  is 
  fundamental 
  also 
  to 
  optics, 
  wire 
  telephony 
  and 
  power 
  

   transmission, 
  it 
  is 
  hoped 
  that 
  the 
  volume 
  may 
  be 
  useful 
  in 
  these 
  

   fields 
  also." 
  

  

  As 
  regards 
  the 
  manner 
  of 
  presentation 
  and 
  attention 
  to 
  prac- 
  

   tical 
  details 
  nothing 
  is 
  left 
  to 
  be 
  desired. 
  In 
  many 
  places 
  where 
  

   the 
  student's 
  previous 
  mathematical 
  attainments 
  may 
  be 
  inade- 
  

   quate, 
  the 
  author 
  has 
  incorporated 
  clear 
  concise 
  proofs 
  of 
  the 
  

   relations 
  and 
  theorems 
  required. 
  This 
  is 
  especially 
  true 
  of 
  the 
  

   complex 
  quantity, 
  of 
  vector 
  algebra, 
  and 
  of 
  ordinary 
  differential 
  

   equations. 
  The 
  judicious 
  use 
  of 
  italic 
  and 
  Clarendon 
  type, 
  the 
  

   employment 
  of 
  Gibbs' 
  notation 
  for 
  dot 
  and 
  cross 
  products, 
  the 
  

   inclusion 
  of 
  illuminating 
  foot-notes 
  throughout 
  and 
  of 
  useful 
  

   tables 
  in 
  the 
  appendix, 
  and 
  the 
  care 
  with 
  which 
  the 
  line 
  dia- 
  

  

  