﻿446 
  Scientific 
  Intelligence. 
  

  

  in 
  this' 
  place. 
  Suffice 
  it 
  to 
  say 
  that 
  the 
  numerical 
  data 
  given 
  and 
  

   the 
  spectrograms 
  reproduced 
  in 
  the 
  paper 
  show 
  that, 
  beyond 
  all 
  

   question, 
  neon 
  contains 
  two 
  isotopes 
  having 
  atomic 
  weights 
  20-00 
  

   and 
  22-00 
  respectively. 
  The 
  accuracy 
  is 
  estimated 
  at 
  about 
  one- 
  

   tenth 
  of 
  one 
  per 
  cent. 
  In 
  order 
  to 
  give 
  the 
  accepted 
  density 
  of 
  

   atmospheric 
  neon 
  the 
  proportions 
  by 
  volume 
  of 
  the 
  lighter 
  and 
  

   heavier 
  isotopes 
  are 
  computed 
  to 
  be 
  respectively 
  90 
  per 
  cent 
  and 
  

   10 
  per 
  cent. 
  The 
  ratio 
  9 
  :1 
  agrees 
  closely 
  with 
  the 
  estimated 
  

   ratio 
  of 
  intensities 
  of 
  the 
  corresponding 
  mass-spectral 
  lines. 
  The 
  

   original 
  paper 
  also 
  contains 
  some 
  evidence 
  for 
  the 
  existence 
  of 
  a 
  

   third 
  isotope, 
  but 
  this 
  question 
  is 
  as 
  yet 
  by 
  no 
  means 
  settled. 
  — 
  

   Phil. 
  Mag., 
  39, 
  449, 
  1920. 
  h. 
  s. 
  u. 
  

  

  7. 
  Lecture 
  Experiments 
  in 
  Acoustics. 
  — 
  The 
  first 
  sentence 
  of 
  

   a 
  recent 
  paper 
  by 
  H. 
  Kayser 
  may 
  be 
  translated 
  as 
  follows 
  : 
  "I 
  

   should 
  like 
  to 
  make 
  known 
  two 
  experiments 
  which 
  I 
  have 
  per- 
  

   formed 
  for 
  many 
  years 
  in 
  my 
  lectures 
  but 
  which, 
  as 
  far 
  as 
  I 
  am 
  

   aware, 
  are 
  otherwise 
  unknown." 
  Since 
  this 
  holds 
  for 
  Germany, 
  

   as 
  the 
  experiments 
  are 
  new 
  to 
  the 
  present 
  writer, 
  and 
  as 
  they 
  

   are 
  undoubtedly 
  very 
  good, 
  it 
  seems 
  desirable 
  to 
  give 
  a 
  free 
  trans- 
  

   la 
  :ion 
  of 
  Kayser 
  ? 
  s 
  account 
  of 
  the 
  demonstrations. 
  

  

  " 
  1. 
  It 
  is 
  in 
  general 
  very 
  difficult 
  to 
  cause 
  an 
  observer, 
  who 
  has 
  

   not 
  a 
  fine-trained 
  musical 
  ear, 
  to 
  hear 
  a 
  combination 
  tone. 
  This 
  

   can 
  be 
  accomplished 
  very 
  easily 
  for 
  a 
  difference 
  tone 
  if 
  this 
  tone 
  

   be 
  made 
  variable 
  instead 
  of 
  constant. 
  I 
  use 
  two 
  small 
  glass 
  

   whistles 
  (each 
  having 
  the 
  form 
  of 
  a 
  sprayer) 
  which 
  give 
  very 
  

   intense 
  notes. 
  The 
  whistle 
  that 
  gives 
  the 
  higher 
  tone 
  is 
  open, 
  

   while 
  the 
  other 
  is 
  closed 
  by 
  a 
  piston 
  which 
  can 
  be 
  readily 
  pushed 
  

   in 
  and 
  drawn 
  out. 
  When 
  the 
  two 
  whistles 
  are 
  blown 
  simul- 
  

   taneously 
  with 
  the 
  mouth 
  the 
  difference 
  tone 
  is 
  produced 
  but, 
  for 
  

   the 
  most 
  part, 
  not 
  detected. 
  If, 
  however, 
  during 
  the 
  blowing, 
  

   the 
  piston 
  be 
  displaced 
  so 
  as 
  to 
  cause 
  the 
  lower 
  tone 
  to 
  rise 
  then 
  

   the 
  frequencies 
  of 
  the 
  two 
  whistles 
  approach 
  each 
  other 
  and 
  

   hence 
  the 
  difference 
  tone 
  falls 
  steadily 
  lower. 
  We 
  then 
  have 
  the 
  

   constant 
  pitch 
  of 
  the 
  first 
  whistle, 
  the 
  rising 
  pitch 
  of 
  the 
  second 
  

   whistle 
  and, 
  at 
  the 
  same 
  time, 
  the 
  falling 
  pitch 
  of 
  the 
  difference 
  

   tone. 
  The 
  sound 
  of 
  this 
  falling 
  note 
  is 
  easily 
  detected 
  even 
  by 
  

   the 
  most 
  untrained 
  observer. 
  ' 
  ' 
  

  

  "2. 
  From 
  the 
  prongs 
  of 
  a 
  vibrating 
  tuning-fork 
  there 
  pro- 
  

   ceed 
  several 
  trains 
  of 
  waves 
  which, 
  due 
  to 
  destructive 
  interfer- 
  

   ence, 
  establish 
  silence 
  in 
  certain 
  directions 
  ; 
  four 
  such 
  directions 
  

   obtaining 
  around 
  the 
  fork. 
  To 
  demonstrate 
  this 
  fact, 
  I 
  set 
  up 
  a 
  

   resonator 
  for 
  the 
  fork-tone 
  by 
  partially 
  filling 
  a 
  cylindrical 
  

   graduate 
  or 
  stand 
  pipe 
  with 
  water 
  to 
  such 
  a 
  depth 
  as 
  to 
  make 
  the 
  

   air 
  column 
  equal 
  to 
  a 
  quarter 
  wave-length 
  of 
  the 
  fork-tone, 
  that 
  

   is, 
  equal 
  to 
  the 
  length 
  of 
  the 
  resonance 
  base-box 
  belonging 
  to 
  the 
  

   fork. 
  If 
  the 
  vibrating 
  fork 
  (unscrewed 
  from 
  its 
  sounding 
  box, 
  

   of 
  course) 
  be 
  held 
  horizontally 
  with 
  its 
  prongs 
  over 
  the 
  open 
  end 
  

   of 
  the 
  tube 
  then, 
  in 
  general, 
  the 
  tone 
  is 
  heard 
  very 
  distinctly. 
  

   If, 
  however, 
  the 
  fork 
  be 
  rotated 
  around 
  the 
  long 
  axis 
  of 
  its 
  stem 
  

  

  