﻿Webster 
  — 
  Producing 
  a 
  Constant 
  Angular 
  velocity. 
  379 
  

  

  Akt. 
  XXX 
  V. 
  — 
  On 
  a 
  means 
  of 
  producing 
  a 
  Constant 
  Angular 
  

   velocity 
  ; 
  by 
  A. 
  G. 
  Webster, 
  Ph.D. 
  

  

  In 
  many 
  physical 
  determinations 
  one 
  of 
  the 
  most 
  important 
  

   elements, 
  and 
  one 
  of 
  the 
  most 
  difficult 
  to 
  maintain 
  constant, 
  is 
  

   a 
  velocity 
  of 
  rotation. 
  If 
  the 
  velocity 
  is 
  very 
  small, 
  and 
  very 
  

   little 
  power 
  is 
  required 
  to 
  be 
  transmitted, 
  a 
  clock-work 
  device 
  

   with 
  some 
  form 
  of 
  escapement 
  is 
  all 
  that 
  could 
  be 
  desired. 
  If 
  

   as 
  much 
  power 
  is 
  needed 
  as 
  is 
  required 
  to 
  drive 
  a 
  large 
  tele- 
  

   scope 
  or 
  siderostat, 
  however, 
  the 
  clockwork 
  becomes 
  expensive, 
  

   and 
  various 
  governing 
  devices 
  other 
  than 
  escapements 
  have 
  to 
  

   be 
  employed, 
  and 
  the 
  very 
  great 
  number 
  of 
  such 
  devices 
  actu- 
  

   ally 
  in 
  use 
  shows 
  how 
  unsatisfactory 
  the 
  method 
  must 
  be. 
  In 
  

   electrical 
  determinations 
  in 
  absolute 
  measure, 
  such 
  as 
  determi- 
  

   nations 
  of 
  the 
  ohm 
  or 
  of 
  " 
  v" 
  clockwork 
  is 
  out 
  of 
  the 
  ques- 
  

   tion, 
  as 
  a 
  high 
  speed 
  has 
  to 
  be 
  kept 
  up, 
  and 
  resort 
  has 
  gener- 
  

   ally 
  been 
  had 
  to 
  water 
  or 
  electrical 
  motors, 
  the 
  speed 
  being 
  

  

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  l 
  

  

  governed 
  by 
  a 
  special 
  observer, 
  who 
  compared 
  the 
  angular 
  

   velocity 
  with 
  the 
  frequency 
  of 
  a 
  tuning 
  fork 
  by 
  some 
  strobo- 
  

   scope 
  method. 
  It 
  has 
  doubtless 
  occurred 
  to 
  many 
  that 
  it 
  

   would 
  be 
  possible 
  to 
  regulate 
  an 
  electric 
  motor 
  by 
  an 
  intermit- 
  

   tent 
  current 
  interrupted 
  directly 
  by 
  a 
  tuning-fork, 
  and 
  such 
  an 
  

   arrangement, 
  proposed 
  by 
  Marcel 
  Deprez, 
  is 
  quoted 
  as 
  one 
  of 
  

   the 
  earliest 
  forms 
  of 
  synchronous 
  motor. 
  I 
  am 
  not 
  aware 
  

   whether 
  the 
  experiment 
  was 
  ever 
  actually 
  carried 
  out 
  ; 
  in 
  any 
  

   case 
  no 
  one 
  seems 
  to 
  have 
  made 
  use 
  of 
  the 
  device 
  in 
  practical 
  

   cases 
  where 
  any 
  amount 
  of 
  power 
  was 
  needed. 
  At 
  the 
  Elec- 
  

   trical 
  Congress 
  in 
  Chicago 
  in 
  1893 
  I 
  read 
  a 
  short 
  note 
  on 
  an 
  

   arrangement 
  that 
  I 
  had 
  used, 
  but 
  as 
  I 
  have 
  had 
  a 
  number 
  of 
  

   inquiries 
  on 
  the 
  subject 
  I 
  think 
  it 
  may 
  be 
  worth 
  while 
  to 
  pub- 
  

   lish 
  the 
  matter 
  in 
  a 
  scientific 
  journal. 
  

  

  