﻿• 
  Webster 
  — 
  Producing 
  a 
  Constant 
  Angular 
  velocity. 
  381 
  

  

  is 
  constant 
  to 
  the 
  limit 
  of 
  constancy 
  of 
  the 
  frequency 
  of 
  the 
  

   tuning-fork. 
  The 
  observer, 
  being 
  released 
  from 
  governing 
  the 
  

   rotation, 
  is 
  at 
  liberty 
  to 
  determine 
  this 
  limit 
  of 
  constancy 
  by 
  

   comparing 
  the 
  fork 
  with 
  a 
  standard 
  by 
  Lissajous's 
  method. 
  In 
  

   this 
  manner 
  I 
  found 
  that 
  it 
  was 
  not 
  difficult 
  to 
  obtain 
  an 
  accu- 
  

   racy 
  for 
  the 
  fork 
  approaching 
  one 
  part 
  in 
  twenty 
  thousand. 
  

   The 
  oscillation 
  of 
  the 
  motor 
  about 
  this 
  mean 
  may 
  be 
  made, 
  by 
  

   means 
  of 
  a 
  fly-wheel, 
  very 
  small. 
  

  

  In 
  throwing 
  on 
  the 
  auxiliary 
  current 
  it 
  is 
  of 
  course 
  necessary 
  

   for 
  the 
  motor 
  to 
  have 
  attained 
  not 
  only 
  the 
  proper 
  velocity, 
  

   but 
  the 
  proper 
  phase. 
  In 
  order 
  to 
  determine 
  this 
  it 
  is 
  neces- 
  

   sary 
  to 
  distinguish 
  between 
  the 
  two 
  bright 
  spots, 
  and 
  this 
  is 
  

   the 
  object 
  of 
  placing 
  the 
  slit 
  S 
  in 
  an 
  unsymmetrical 
  jDOsition 
  

   with 
  respect 
  to 
  the 
  vibration, 
  so 
  that 
  the 
  two 
  arcs 
  are 
  not 
  oppo- 
  

   site 
  each 
  other. 
  The 
  proper 
  position 
  of 
  the 
  arcs 
  for 
  throwing 
  

   on 
  the 
  current 
  is 
  determined 
  by 
  a 
  few 
  trials, 
  and 
  may 
  be 
  

   marked 
  on 
  the 
  screen. 
  In 
  order 
  to 
  warn 
  the 
  observer 
  of 
  a 
  

   violent 
  oscillation, 
  if 
  he 
  is 
  not 
  looking 
  at 
  the 
  screen, 
  a 
  tele- 
  

   phone 
  may 
  be 
  placed 
  in 
  shunt 
  with 
  the 
  brushes 
  of 
  the 
  auxiliary 
  

   armature, 
  and 
  will, 
  if 
  the 
  synchronism 
  fails, 
  by 
  its 
  loud 
  beats 
  

   call 
  the 
  observer 
  even 
  from 
  the 
  next 
  room. 
  I 
  believe 
  a 
  device 
  

   of 
  this 
  sort 
  has 
  been 
  patented 
  by 
  one 
  of 
  the 
  great 
  companies 
  

   for 
  the 
  purpose 
  of 
  indicating 
  the 
  phase 
  of 
  alternators 
  to 
  be 
  

   run 
  in 
  parallel 
  — 
  I 
  presume 
  it 
  is 
  possible 
  to 
  patent 
  the 
  use 
  of 
  a 
  

   telephone 
  for 
  waking 
  one 
  in 
  the 
  morning, 
  or 
  anything 
  else, 
  

   but 
  such 
  an 
  arrangement 
  appears 
  trivial, 
  — 
  it 
  was 
  used 
  by 
  me 
  

   more 
  than 
  four 
  years 
  ago. 
  

  

  In 
  order 
  to 
  test 
  the 
  method 
  practically 
  by 
  the 
  transmission 
  

   of 
  some 
  power, 
  two 
  years 
  ago 
  I 
  belted 
  to 
  the 
  pulley 
  of 
  the 
  

   motor 
  a 
  heavy 
  cone-pulley 
  running 
  nicely 
  on 
  points, 
  and 
  that 
  

   to 
  the 
  cone-pulley 
  of 
  a 
  lathe 
  of 
  twelve 
  inches 
  swing. 
  The 
  

   lathe 
  had 
  a 
  heavy 
  fly-wheel 
  for 
  foot- 
  power, 
  which 
  was 
  belted 
  

   to 
  the 
  pulley 
  to 
  take 
  up 
  the 
  power 
  and 
  furnish 
  a 
  means 
  of 
  check- 
  

   ing 
  oscillations. 
  A 
  cord 
  running 
  over 
  the 
  intermediate 
  cone 
  

   pulley 
  and 
  carrying 
  a 
  number 
  of 
  weights 
  furnished 
  the 
  means 
  

   of 
  absorbing 
  most 
  of 
  the 
  power. 
  The 
  motor 
  was 
  run 
  by 
  

   means 
  of 
  an 
  Edison 
  dynamo 
  designed 
  for 
  110 
  volts, 
  but 
  by 
  

   means 
  of 
  resistance 
  in 
  the 
  field 
  the 
  voltage 
  was 
  brought 
  down, 
  

   so 
  that 
  of 
  course 
  the 
  regulation 
  of 
  the 
  potential 
  was 
  not 
  very 
  

   good. 
  The 
  results 
  therefore 
  exhibit 
  the 
  method 
  at 
  its 
  worst, 
  

   while 
  driving 
  from 
  a 
  storage 
  battery 
  would 
  give 
  far 
  better 
  

   results. 
  The 
  frequency 
  of 
  the 
  fork 
  used 
  was 
  twenty-five 
  per 
  

   second. 
  The 
  gearing 
  ran 
  the 
  lathe 
  at 
  at 
  least 
  twice 
  its 
  ordinary 
  

   speed, 
  the 
  large 
  treadle-pulley 
  making 
  3'8 
  revolutions 
  per 
  

   second, 
  and 
  causing 
  considerable 
  vibration. 
  In 
  the 
  first 
  run 
  

   the 
  armature 
  had 
  47 
  volts 
  at 
  the 
  brushes, 
  and 
  12 
  amperes. 
  The 
  

   governing 
  current 
  was 
  then 
  1*9 
  amperes 
  (mean 
  intermittent). 
  

  

  