﻿394 
  Prof. 
  J. 
  Trowbridge 
  on 
  the 
  Induction 
  Coil. 
  

  

  found 
  necessary 
  to 
  use 
  glass 
  at 
  least 
  one 
  eighth 
  of 
  an 
  inch 
  

   thick 
  between 
  the 
  sectional 
  coils, 
  on 
  account 
  of 
  the 
  great 
  

   electric 
  density 
  developed. 
  Mr. 
  Heinze's 
  experience 
  in 
  this 
  

   respect 
  corroborates 
  my 
  own. 
  In 
  employing 
  a 
  storage- 
  

   battery 
  of 
  twenty 
  thousand 
  cells 
  with 
  an 
  electromotive 
  force 
  

   of 
  forty 
  thousand 
  volts 
  to 
  charge 
  Franklin 
  plates, 
  I 
  have 
  

   found 
  it 
  necessary 
  to 
  also 
  employ 
  plates 
  of 
  glass 
  one 
  eighth 
  

   of 
  an 
  inch 
  thick. 
  The 
  great 
  surface-density 
  developed 
  by 
  a 
  

   powerful 
  rush 
  of 
  current 
  into 
  such 
  condensers 
  to 
  raise 
  them 
  

   to 
  a 
  difference 
  of 
  potential 
  of 
  even 
  five 
  or 
  ten 
  thousand 
  volts, 
  

   makes 
  it 
  unsafe 
  to 
  employ 
  glass 
  of 
  less 
  thickness 
  than 
  one 
  

   eighth 
  of 
  an 
  inch. 
  

  

  When 
  this 
  coil 
  is 
  excited 
  by 
  five 
  storage-cells 
  and 
  is 
  

   provided 
  with 
  a 
  condenser 
  in 
  the 
  primary, 
  it 
  gives, 
  under 
  the 
  

   effect 
  of 
  an 
  ordinary 
  vibrating 
  break, 
  a 
  fifteen-inch 
  spark. 
  

   When, 
  however, 
  the 
  condenser 
  is 
  removed, 
  and 
  the 
  coil 
  is 
  

   operated 
  by 
  a 
  liquid 
  interrupter 
  shown 
  in 
  fig. 
  1, 
  the 
  length 
  

   of 
  spark 
  is 
  increased 
  to 
  thirty 
  inches 
  and 
  is 
  of 
  astonishing 
  

   body. 
  

  

  The 
  interrupter 
  is 
  contained 
  in 
  a 
  wooden 
  box 
  A 
  (fig. 
  1), 
  

   the 
  cover 
  of 
  which 
  swings 
  on 
  hinges 
  and 
  supports 
  all 
  the 
  

   mechanism. 
  By 
  lifting 
  the 
  cover, 
  the 
  parts 
  can 
  be 
  easily 
  

   examined. 
  The 
  front 
  of 
  the 
  box 
  consists 
  of 
  a 
  door 
  which, 
  

   when 
  open, 
  exposes 
  a 
  glass 
  jar 
  C 
  containing 
  acidulated 
  water, 
  

   through 
  which 
  the 
  mechanism 
  can 
  be 
  seen. 
  A 
  small 
  motor 
  

   on 
  the 
  top 
  of 
  the 
  box 
  drives 
  the 
  oscillating 
  mechanism, 
  

   which 
  consists 
  of 
  a 
  base-casting 
  E 
  having 
  a 
  bearing 
  and 
  a 
  

   shaft 
  F, 
  upon 
  one 
  end 
  of 
  which 
  is 
  a 
  crank-disk 
  G, 
  and 
  at 
  the 
  

   other 
  end 
  a 
  pulley 
  for 
  receiving 
  its 
  power 
  from 
  the 
  motor. 
  

   By 
  the 
  rotation 
  of 
  disk 
  G 
  and 
  crank-pin 
  H, 
  an 
  up 
  and 
  down 
  

   movement 
  is 
  imparted 
  to 
  a 
  brass 
  sleeve 
  I, 
  which 
  moves 
  up 
  

   and 
  down 
  upon 
  a 
  vertical 
  spindle 
  J 
  secured 
  to 
  the 
  base- 
  

   casting 
  E. 
  This 
  sleeve 
  I 
  has 
  adjustably 
  secured 
  to 
  it 
  a 
  

   platinum 
  wire 
  K, 
  which 
  projects 
  below 
  the 
  cover 
  B, 
  and 
  

   moves 
  in 
  and 
  out 
  through 
  a 
  capillary 
  tube 
  closely 
  fitting 
  the 
  

   wire. 
  This 
  glass 
  tube 
  L 
  is 
  held 
  in 
  a 
  lead 
  electrode 
  M, 
  so 
  

   constructed 
  as 
  to 
  partly 
  surround 
  and 
  to 
  come 
  very 
  close 
  to 
  

   the 
  platinum 
  wire 
  when 
  the 
  latter 
  projects 
  through 
  the 
  

   capillary 
  tube. 
  The 
  electrode 
  M, 
  glass 
  tube 
  L, 
  and 
  platinum 
  

   wire 
  K 
  are 
  immersed 
  in 
  the 
  acidulated 
  solution, 
  so 
  that 
  the 
  

   end 
  of 
  the 
  capillary 
  tube 
  is 
  about 
  an 
  inch 
  below 
  the 
  top 
  of 
  

   the 
  liquid 
  N. 
  The 
  liquid 
  is 
  a 
  twenty 
  per 
  cent, 
  solution 
  of 
  

   sulphuric 
  acid. 
  The 
  crank-disk 
  G 
  is 
  made 
  of 
  slate, 
  and 
  has 
  

   upon 
  its 
  periphery 
  a 
  90-degree 
  segment 
  of 
  brass 
  which 
  is 
  

   connected 
  to 
  the 
  shaft 
  F. 
  The 
  segment 
  bears 
  a 
  certain 
  

   relation 
  in 
  position 
  to 
  brass 
  sleeve 
  1 
  and 
  depth 
  of 
  platinum 
  

  

  