﻿THE 
  UNFELT 
  EARTHQUAKE. 
  235 
  

  

  nh. 
  16m. 
  47s. 
  G. 
  M. 
  T., 
  and 
  have 
  a 
  maximum 
  between 
  nh. 
  22m. 
  and 
  

   nh. 
  24*5111. 
  The 
  second 
  phase 
  commences 
  at 
  11 
  h. 
  2675 
  m. 
  and 
  

   reaches 
  a 
  maximum 
  at 
  I 
  ih. 
  28*25 
  m. 
  Dr. 
  Baratta 
  points 
  out 
  that 
  

   after 
  nh. 
  35m. 
  there 
  is 
  a 
  marked 
  change 
  in 
  the 
  character 
  of 
  the 
  

   curve, 
  and 
  instead 
  of 
  the 
  oscillations 
  of 
  the 
  pendulum 
  being 
  made 
  

   evenly 
  on 
  either 
  side 
  of 
  a 
  central 
  line, 
  they 
  are 
  made 
  on 
  either 
  side 
  

   of 
  a 
  sinuous 
  line 
  such 
  as 
  would 
  be 
  due 
  to 
  a 
  slow 
  tilting 
  of 
  the 
  whole 
  

   instrument 
  backwards 
  and 
  forwards. 
  The 
  well 
  marked 
  slow 
  undu- 
  

   lations 
  set 
  in 
  at 
  about 
  nh. 
  42m. 
  30s. 
  and 
  attain 
  their 
  maximum 
  

   at 
  nh. 
  47m. 
  10s. 
  The 
  disturbance 
  continued 
  till 
  13b. 
  30m. 
  G. 
  M. 
  T. 
  

  

  The 
  long 
  pendulum 
  of 
  10 
  metres 
  gave 
  a 
  diagram 
  showing 
  the 
  

   commencement 
  of 
  the 
  disturbance 
  atuh. 
  17m. 
  and 
  its 
  cessation 
  

   at 
  about 
  1 
  5h. 
  G. 
  M, 
  T. 
  The 
  greater 
  duration 
  of 
  the 
  disturbance 
  

   on 
  this 
  instrument 
  is 
  due 
  to 
  its 
  greater 
  sensitiveness. 
  

  

  The 
  horizontal 
  displacement 
  of 
  the 
  pendulum 
  bob 
  during 
  the 
  first 
  

   phase 
  amounts 
  to 
  as 
  much 
  as 
  '5 
  mm., 
  and 
  between 
  1 
  ih. 
  27 
  and 
  1 
  ih. 
  33m. 
  

   the 
  maximum 
  displacement 
  attained 
  is 
  •47mm., 
  or 
  nearly 
  as 
  much. 
  

   The 
  displacement 
  atuh. 
  47m., 
  if 
  wholely 
  due 
  to 
  tilting 
  of 
  the 
  

   instrument, 
  shows 
  a 
  tilt 
  of 
  22" 
  of 
  arc 
  from 
  the 
  vertical. 
  

  

  Catania. 
  — 
  I 
  have 
  received 
  from 
  Prof. 
  A. 
  Ricco, 
  Director 
  of 
  the 
  

   Royal 
  Observatory, 
  three 
  copies 
  of 
  the 
  records 
  of 
  his 
  two 
  seismo- 
  

   graphs 
  ; 
  one 
  of 
  these 
  only 
  gives 
  a 
  record 
  of 
  one 
  minute 
  duration 
  and 
  

   the 
  diagram 
  is 
  consequently 
  not 
  of 
  great 
  interest. 
  The 
  other 
  has 
  a 
  

   continuous 
  record 
  ; 
  it 
  is, 
  like 
  most 
  of 
  the 
  Italian 
  instruments, 
  a 
  

   simple 
  pendulum, 
  of 
  25*30 
  metres 
  length 
  and 
  200 
  kg. 
  weight, 
  whose 
  

   movement 
  is 
  magnified 
  12*5 
  times 
  and 
  recorded 
  on 
  a 
  paper 
  moving 
  

   at 
  the 
  rate 
  of 
  o*6 
  metres 
  per 
  hour. 
  1 
  The 
  components 
  are 
  registered 
  in 
  

   NE-SVV 
  and 
  N 
  W-SE 
  directions. 
  

  

  The 
  disturbance 
  of 
  the 
  trace, 
  which 
  is 
  reproduced 
  on 
  Plate 
  XLI, 
  

   commences 
  at 
  nh. 
  17m. 
  23s. 
  the 
  total 
  displacement 
  of 
  the 
  weight 
  

   being 
  *3 
  mm. 
  from 
  the 
  vertical. 
  The 
  commencement 
  of 
  the 
  second 
  

  

  1 
  A 
  description 
  of 
  this 
  instrument, 
  written 
  by 
  Prof. 
  Ricco, 
  will 
  be 
  found 
  in 
  the 
  Atti 
  dell. 
  

   Ac. 
  Gioenia 
  de 
  Sci. 
  Nat. 
  in 
  Catani, 
  4th 
  secies, 
  X. 
  

  

  (235 
  ) 
  

  

  