﻿electric 
  Effects. 
  189 
  

  

  of 
  aliquot 
  part 
  of 
  the 
  natural 
  period 
  of 
  vibration 
  of 
  the 
  needle. 
  

   In 
  this 
  case 
  it 
  is 
  conceivable 
  that 
  they 
  might, 
  if 
  sufficiently 
  prolonged, 
  

   in 
  time 
  give 
  rise 
  to 
  a 
  swing 
  of 
  the 
  needle, 
  much 
  in 
  excess 
  of 
  the 
  

   actual 
  angular 
  disturbances, 
  but 
  this 
  supposition 
  is 
  improbable, 
  

   for 
  it 
  is 
  probable 
  that 
  the 
  wave 
  motion 
  was 
  by 
  no 
  means 
  uniform 
  and 
  

   the 
  required 
  ratio 
  between 
  the 
  period 
  of 
  the 
  wave 
  and 
  that 
  of 
  the 
  

   magnet 
  would 
  not 
  last 
  for 
  long 
  enough 
  to 
  produce 
  the 
  observed 
  effect. 
  

   On 
  the 
  whole, 
  therefore, 
  it 
  is 
  probable 
  that 
  the 
  disturbance 
  of 
  

   the 
  magnetic 
  instruments 
  was 
  partly, 
  if 
  not 
  principally, 
  magnetic 
  and 
  

   not 
  mechanical 
  ; 
  but 
  it 
  is 
  evident, 
  from 
  the 
  time 
  at 
  which 
  they 
  were 
  

   felt, 
  that 
  they 
  had 
  no 
  direct 
  connection 
  with 
  the 
  electric 
  disturbances 
  

   described 
  in 
  the 
  next 
  chapter. 
  We 
  have 
  already 
  seen 
  (Chap. 
  IV) 
  

   that 
  the 
  magnetic 
  disturbances 
  were 
  felt 
  at 
  Bombay 
  at 
  the 
  

   exact 
  time 
  when 
  the 
  earthquake-wave 
  must 
  have 
  passed 
  under 
  

   it, 
  and, 
  consequently, 
  if 
  the 
  apparently 
  magnetic 
  disturbance 
  

   at 
  Colaba 
  was 
  really, 
  as 
  is 
  probable, 
  magnetic, 
  it 
  must 
  have 
  

   originated 
  locally, 
  and 
  as 
  a 
  direct 
  consequence 
  of 
  the 
  passage 
  

   of 
  the 
  earthquake-wave. 
  This 
  conclusion 
  is 
  also 
  in 
  agreement 
  

   with 
  the 
  facts 
  recorded 
  in 
  Chapter 
  XV, 
  regarding 
  the 
  general 
  

   agreement 
  of 
  time 
  of 
  the 
  disturbance 
  of 
  such 
  magnetic 
  instruments 
  

   in 
  Europe 
  as 
  were 
  affected, 
  with 
  that 
  of 
  the 
  passage 
  of 
  the 
  earth- 
  

   quake 
  waves, 
  and 
  with 
  the 
  absence 
  of 
  a 
  dose 
  agreement 
  of 
  the 
  

   times 
  at 
  which 
  the 
  magnetic 
  traces 
  were 
  affected 
  with 
  any 
  of 
  the 
  

   phases 
  of 
  the 
  mechanical 
  disturbance. 
  

  

  Chapter 
  XII.— 
  ELECTRIC 
  EFFECTS. 
  

  

  Changes 
  in 
  the 
  electrical 
  state 
  of 
  the 
  atmosphere 
  and 
  earth 
  currents, 
  

   causing 
  a 
  temporary 
  interruption 
  of 
  telegraphic 
  communication, 
  

   have 
  been 
  observed 
  to 
  accompany 
  other 
  earthquakes, 
  but 
  in 
  none, 
  

   so 
  far 
  as 
  I 
  know, 
  have 
  the 
  latter 
  been 
  so 
  conspicuous 
  and 
  severe 
  

   as 
  in 
  the 
  present 
  instance. 
  

  

  Among 
  the 
  reports 
  received 
  from 
  the 
  Telegraph 
  Department 
  

   several 
  mention 
  interruptions 
  of 
  communication 
  at 
  about 
  the 
  time 
  

  

  ( 
  i89 
  ) 
  

  

  