﻿kin 
  ''-effect 
  in 
  Electrical 
  Oscillators. 
  433 
  

  

  With 
  those 
  2*5 
  cms. 
  and 
  4 
  cms. 
  in 
  diameter, 
  knobs 
  K, 
  K 
  of 
  

   diameter 
  19 
  mm. 
  were 
  used. 
  When 
  the 
  spheres 
  had 
  a 
  

   diameter 
  of 
  10 
  cms., 
  the 
  knobs 
  had 
  a 
  diameter 
  of 
  37 
  mm. 
  

  

  The 
  membrane 
  m, 
  m 
  was 
  first 
  softened 
  by 
  soaking 
  for 
  a 
  

   few 
  minutes 
  in 
  water 
  and 
  glycerine, 
  and 
  was 
  then 
  securely 
  

   bound 
  to 
  the 
  circumference 
  of 
  the 
  hard 
  rubber 
  disks 
  by 
  cords 
  

   which 
  rested 
  in 
  grooves 
  made 
  to 
  receive 
  them. 
  The 
  mem- 
  

   brane 
  was 
  such 
  as 
  is 
  used 
  as 
  a 
  container 
  for 
  the 
  familiar 
  

   ■ 
  Bologna 
  sausage,' 
  and 
  was 
  obtained 
  at 
  a 
  large 
  packing 
  

   house. 
  It 
  made 
  a 
  perfectly 
  oil-tight 
  vessel, 
  the 
  largest 
  

   oscillator 
  being 
  in 
  action 
  for 
  hours 
  without 
  a 
  single 
  drop 
  of 
  

   oil 
  escaping. 
  

  

  The 
  oil 
  used 
  was 
  described 
  as 
  ivhite 
  liquid 
  vaseline 
  

  

  When 
  in 
  operation 
  the 
  oscillator 
  was 
  placed 
  in 
  the 
  para- 
  

   bolic 
  reflector 
  on 
  a 
  suitable 
  support, 
  seen 
  in 
  fig. 
  7, 
  and 
  was 
  

   connected 
  to 
  the 
  coil 
  by 
  wires 
  L, 
  L 
  passing 
  through 
  tubes 
  as 
  

   in 
  the 
  case 
  of 
  the 
  cylinders. 
  

  

  The 
  interrupter 
  was 
  that 
  used 
  by 
  G. 
  W. 
  Pierce 
  with 
  his 
  

   Radio-micrometer 
  *. 
  It 
  consisted 
  of 
  a 
  platinum-tipped 
  rod 
  

   which, 
  by 
  means 
  of 
  a 
  fan-motor, 
  was 
  rapidly 
  plunged 
  into 
  

   and 
  withdrawn 
  from 
  a 
  cup 
  of 
  mercury, 
  the 
  surface 
  of 
  which 
  

   was 
  kept 
  clean 
  by 
  a 
  stream 
  of 
  water 
  continually 
  flowing 
  over 
  

   it. 
  In 
  series 
  with 
  the 
  interrupter 
  was 
  a 
  pendulum 
  contact- 
  

   maker. 
  The 
  metallic 
  rod 
  of 
  the 
  pendulum 
  carried 
  a 
  platinum 
  

   wire 
  soldered 
  to 
  its 
  lower 
  end, 
  which, 
  as 
  the 
  pendulum 
  swung 
  

   to 
  and 
  fro, 
  dipped 
  into 
  a 
  mercury 
  trough. 
  By 
  raising 
  or 
  

   lowering 
  the 
  pendulum 
  the 
  time 
  during 
  which 
  it 
  was 
  im- 
  

   mersed 
  in 
  the 
  mercury 
  was 
  shortened 
  or 
  lengthened. 
  This 
  

   was 
  so 
  adjusted 
  that 
  whilst 
  the 
  pendulum 
  made 
  circuit 
  during 
  

   a 
  single 
  semi-oscillation, 
  the 
  motor-break 
  made 
  about 
  6 
  inter- 
  

   ruptions. 
  In 
  addition 
  an 
  ordinary 
  key 
  was 
  in 
  circuit. 
  This 
  

   was 
  pressed 
  down 
  while 
  the 
  pendulum 
  made 
  any 
  desired 
  

   number 
  of 
  vibrations. 
  For 
  most 
  of 
  the 
  work 
  the 
  key 
  was 
  

   depressed 
  for 
  10 
  swings 
  of 
  the 
  pendulum, 
  that 
  is, 
  for 
  about 
  

   60 
  interruptions 
  of 
  the 
  coil. 
  Thus 
  in 
  the 
  primary 
  circuit 
  the 
  

   current 
  traversed 
  in 
  succession 
  the 
  primary 
  of 
  the 
  induction- 
  

   coil, 
  the 
  motor-break, 
  the. 
  pendulum 
  rod 
  into 
  the 
  mercury 
  

   and 
  the 
  circuit-key. 
  The 
  battery 
  consisted 
  of 
  ten 
  storage- 
  

   cells 
  arranged 
  in 
  two 
  banks 
  in 
  multiple, 
  i. 
  e. 
  giving 
  10 
  volts 
  

   of 
  E.M.F. 
  

  

  The 
  parabolic 
  mirrors, 
  both 
  for 
  oscillator 
  and 
  receiver, 
  

   were 
  75 
  cms. 
  high, 
  60 
  cms. 
  wide, 
  and 
  had 
  a 
  focal 
  length 
  of 
  

   12*5 
  cms. 
  At 
  first 
  reflectors 
  of 
  but 
  5 
  cms. 
  focal 
  length 
  were 
  

  

  * 
  American 
  Jour, 
  of 
  Science, 
  vol. 
  ix. 
  p. 
  252 
  (1900). 
  

  

  