﻿Trowbridge 
  — 
  Investigation 
  of 
  the 
  Coherer. 
  205 
  

  

  a 
  steady 
  current 
  will 
  produce 
  coherer 
  action 
  if 
  the 
  potential 
  

   difference 
  between 
  the 
  ends 
  of 
  the 
  coherer 
  exceed 
  what 
  I 
  have 
  

   called 
  the 
  critical 
  voltage, 
  and 
  since 
  the 
  lower 
  this 
  critical 
  

   value 
  is, 
  the 
  more 
  sensitive 
  will 
  be 
  the 
  coherer 
  for 
  long-dis- 
  

   tance 
  work, 
  care 
  must 
  be 
  taken 
  that 
  the 
  electromotive 
  force 
  of 
  

   the 
  battery 
  which 
  operates 
  the 
  relay 
  in 
  Marconi's 
  arrangement, 
  

   shall 
  have 
  a 
  value 
  less 
  than 
  the 
  critical 
  value 
  for 
  the 
  coherer 
  

   used. 
  

  

  If 
  an 
  electromotive 
  force 
  of 
  about 
  the 
  critical 
  value 
  is 
  used, 
  

   we 
  might 
  expect 
  to 
  notice 
  a 
  confusion 
  of 
  the 
  signals 
  from 
  the 
  

   sending 
  station 
  due 
  to 
  the 
  local 
  circuit 
  through 
  the 
  coherer 
  

   producing 
  an 
  independent 
  and 
  quite 
  irregular 
  lowering 
  of 
  the 
  

   resistance. 
  

  

  Everyone 
  who 
  has 
  attempted 
  wireless 
  telegraphy 
  has 
  proba- 
  

   bly 
  been 
  annoyed 
  by 
  extra 
  "clicks" 
  of 
  the 
  instrument. 
  I 
  

   believe 
  it 
  is 
  in 
  many 
  cases 
  attributable 
  to 
  the 
  cause 
  just 
  men- 
  

   tioned 
  ; 
  in 
  which 
  case 
  it 
  could 
  be 
  done 
  away 
  with 
  by 
  so 
  

   choosing 
  critical 
  potential 
  of 
  coherer, 
  electromotive 
  force 
  of 
  

   battery 
  in 
  coherer 
  circuit, 
  and 
  sensibility 
  of 
  the 
  relay, 
  that 
  the 
  

   first 
  should 
  be 
  higher 
  than 
  the 
  second, 
  while 
  the 
  third 
  should 
  

   be 
  great 
  enough 
  to 
  permit 
  of 
  a 
  small 
  absolute 
  value 
  of 
  the 
  

   other 
  two. 
  

  

  In 
  conclusion, 
  I 
  should 
  like 
  to 
  take 
  this 
  opportunity 
  to 
  

   express 
  my 
  thanks 
  to 
  my 
  colleague, 
  Dr. 
  Karl 
  Guthe, 
  for 
  his 
  

   kindly 
  interest 
  in 
  the 
  present 
  investigation, 
  and 
  for 
  numerous 
  

   helpful 
  suggestions. 
  

  

  Physical 
  Laboratory 
  of 
  the 
  University 
  of 
  Michigan, 
  June, 
  1899. 
  

  

  