﻿124 
  Prof. 
  E. 
  H. 
  Barton 
  on 
  Range 
  and 
  

  

  he 
  showed 
  that 
  the 
  logarithmic 
  decrements 
  involved 
  might 
  

   be 
  deduced 
  from 
  the 
  proportions 
  of 
  the 
  resulting 
  resonance 
  

   curve. 
  But 
  it 
  does 
  not 
  appear 
  that 
  he 
  pointed 
  out 
  the 
  

   possibility 
  of 
  any 
  variation 
  of 
  the 
  sharpness 
  of 
  resonance 
  

   with 
  frequency 
  while 
  the 
  damping 
  coefficient 
  remained 
  

   constant. 
  

  

  Indeed, 
  it 
  is 
  quite 
  possible 
  that 
  for 
  the 
  cases 
  then 
  under 
  

   examination, 
  no 
  such 
  simple 
  relation 
  held 
  as 
  that 
  here 
  

   deduced 
  for 
  the 
  case 
  of 
  forcing 
  of 
  sustained 
  amplitude. 
  

   For, 
  in 
  the 
  cases 
  usually 
  dealt 
  with 
  by 
  Bjerknes, 
  the 
  forcing 
  

   was 
  due 
  to 
  the 
  oscillations 
  in 
  a 
  Hertzian 
  oscillator 
  and 
  was 
  

   strongly 
  damped. 
  The 
  responsive 
  system 
  was 
  usually 
  a 
  

   Hertzian 
  resonator 
  in 
  which 
  the 
  damping 
  was 
  relatively 
  

   small. 
  

  

  Zenneck 
  on 
  Sharpness 
  of 
  Resonance. 
  — 
  In 
  his 
  treatise 
  on 
  

   Wireless 
  Telegraphy, 
  &c.*, 
  J. 
  Zenneck 
  plots 
  a 
  resonance 
  

   curve, 
  with 
  certain 
  specified 
  coordinates, 
  and 
  takes 
  as 
  a 
  

   measure 
  of 
  the 
  sharpness 
  of 
  resonance 
  the 
  curvature 
  of 
  this 
  

   resonance 
  curve 
  at 
  its 
  summit. 
  It 
  is 
  then 
  showm 
  that 
  this 
  

   curvature 
  is 
  proportional 
  to 
  the 
  inverse 
  square 
  of 
  the 
  

   logarithmic 
  decrement. 
  

  

  He 
  does 
  not, 
  however, 
  appear 
  to 
  make 
  any 
  use 
  of 
  the 
  

   result 
  or 
  to 
  analyse 
  the 
  decrement 
  into 
  its 
  factors. 
  

  

  Raman 
  on 
  Maintenance 
  of 
  Oscillations. 
  — 
  In 
  dealing 
  with 
  

   vibrations 
  maintained 
  by 
  a 
  periodic 
  variation 
  of 
  the 
  spring 
  f 
  , 
  

   C. 
  Y. 
  Raman 
  has 
  the 
  following 
  pertinent 
  remark 
  : 
  — 
  

  

  " 
  If 
  the 
  frequency 
  of 
  the 
  imposed 
  variation 
  of 
  ' 
  spring 
  ' 
  

   were 
  60 
  per 
  second, 
  the 
  oscillations 
  of 
  the 
  system 
  would 
  be 
  

   maintained 
  (under 
  suitable 
  circumstances) 
  if 
  the 
  frequency 
  

   of 
  its 
  free 
  oscillations 
  were 
  nearly 
  equal 
  to 
  30 
  or 
  60 
  or 
  90 
  or 
  

   120 
  or 
  150 
  and 
  so 
  on, 
  the 
  degree 
  of 
  approximation 
  to 
  equality 
  

   necessary 
  increasing 
  as 
  we 
  proceed 
  up 
  the 
  series. 
  The 
  

   frequency 
  of 
  the 
  maintained 
  oscillation 
  would 
  be 
  exactly 
  30 
  

   or 
  60 
  or 
  90 
  and 
  so 
  on 
  " 
  J. 
  

  

  It 
  is 
  accordingly 
  seen 
  that 
  the 
  view 
  insisted 
  upon 
  in 
  the 
  

   present 
  paper 
  for 
  ordinary 
  forced 
  vibrations 
  has 
  its 
  counter- 
  

   part 
  in 
  the 
  maintained 
  oscillations 
  treated 
  by 
  Raman. 
  And 
  

   further, 
  that 
  this 
  feature, 
  overlooked 
  by 
  most 
  for 
  the 
  ordinary 
  

   vibrations, 
  has 
  been 
  recognized 
  by 
  the 
  Calcutta 
  physicist 
  

   with 
  respect 
  to 
  these 
  special 
  ones. 
  

  

  * 
  Elektromagtietische 
  Sckwingimgen 
  und 
  Di'ahtlose 
  Telegraphie, 
  Art. 
  312, 
  

   p. 
  572, 
  Stuttgart, 
  1905. 
  

  

  t 
  '* 
  The 
  Maintenance 
  of 
  Forced 
  Oscillations 
  of 
  a 
  New 
  Type," 
  Phil. 
  

   31ag\ 
  xxiv. 
  pp. 
  513-520, 
  Oct. 
  1912. 
  

  

  \ 
  Ibid, 
  p, 
  517. 
  

  

  