﻿504 
  Geological 
  Society: 
  — 
  

  

  d' 
  utilisation 
  ' 
  of 
  M. 
  Kutot, 
  and 
  we 
  should 
  expect 
  to 
  find 
  on 
  the 
  

   opposite 
  edges 
  of 
  the 
  flint 
  the 
  ' 
  surface 
  d' 
  accommodation,' 
  as 
  in 
  

   fact 
  we 
  do. 
  

  

  A 
  singular 
  feature, 
  which 
  seems 
  difficult 
  to 
  reconcile 
  with 
  its 
  use 
  

   as 
  an 
  implement, 
  is 
  the 
  restriction 
  of 
  the 
  flaking 
  on 
  one 
  edge 
  to 
  the 
  

   weathered 
  crust. 
  

  

  The 
  origin 
  of 
  the 
  flaking 
  is 
  discussed, 
  and 
  the 
  author, 
  while 
  

   admitting 
  that 
  the 
  fashioning 
  of 
  the 
  flint 
  is 
  not 
  inconsistent 
  with 
  

   intelligent 
  design, 
  concludes 
  that 
  the 
  evidence 
  is 
  not 
  sufficient 
  to 
  

   establish 
  this 
  beyond 
  dispute. 
  It 
  is 
  eminently 
  a 
  case 
  of-' 
  not 
  proven.' 
  

  

  February 
  6th.— 
  Dr. 
  Alfred 
  Harker, 
  F.H.S., 
  President, 
  

   in 
  the 
  Chair. 
  

   The 
  following 
  communication 
  was 
  read 
  : 
  — 
  

  

  ' 
  Some 
  Considerations 
  arising 
  from 
  the 
  Frequency 
  of 
  Earth- 
  

   quakes.' 
  By 
  Kichard 
  Dixon 
  Oldham, 
  F.E.S., 
  F.G.S. 
  

  

  The 
  publication* 
  of 
  an 
  abstract 
  of 
  twenty 
  years' 
  record 
  of 
  earth- 
  

   quakes 
  in 
  Italy 
  gives 
  an 
  opportunity 
  for 
  studying 
  the 
  effect 
  of 
  the 
  

   gravitational 
  attraction 
  of 
  the 
  sun 
  ; 
  the 
  period 
  is 
  so 
  nearly 
  coin- 
  

   cident 
  with 
  the 
  lunar 
  cycles 
  of 
  19 
  and 
  186 
  } 
  r 
  ears 
  that 
  the 
  effect 
  of 
  

   the 
  moon 
  may 
  be 
  regarded 
  as 
  eliminated, 
  the 
  record 
  is 
  of 
  excep- 
  

   tional 
  continuity 
  and 
  completeness, 
  and 
  the 
  number 
  of 
  observations 
  

   is 
  large 
  enough 
  to 
  allow 
  of 
  the 
  extraction 
  of 
  groups 
  sufficiently 
  

   numerous 
  to 
  give 
  good 
  averages. 
  

  

  The 
  distribution 
  of 
  the 
  stresses 
  is 
  dealt 
  with 
  in 
  text-books 
  ; 
  there 
  

   is 
  a 
  maximum 
  upward 
  stress, 
  in 
  diminution 
  of 
  the 
  earth's 
  attraction 
  

   at 
  its 
  surface, 
  at 
  the 
  two 
  points 
  where 
  the 
  sun 
  is 
  in 
  the 
  zenith 
  or 
  

   nadir, 
  and 
  a 
  maximum 
  downward 
  stress 
  along 
  the 
  great 
  circle 
  

   where 
  it 
  is 
  on 
  the 
  horizon 
  ; 
  but 
  as, 
  for 
  the 
  purpose 
  of 
  this 
  investi- 
  

   gation, 
  a 
  decrease 
  of 
  downward 
  pressure 
  is 
  equivalent 
  to 
  an 
  increase 
  

   of 
  upward, 
  I 
  shall 
  take 
  the 
  line 
  along 
  which 
  the 
  downward 
  stress 
  is 
  

   greatest 
  as 
  the 
  zero 
  -line, 
  and 
  express 
  the 
  amount 
  of 
  stress 
  at 
  any 
  

   other 
  time 
  or 
  place 
  as 
  a 
  fraction 
  of 
  the 
  difference 
  between 
  the 
  net 
  

   force 
  of 
  gravity 
  along 
  this 
  line 
  and 
  at 
  the 
  point 
  where 
  the 
  sun 
  is 
  

   in 
  the 
  zenith. 
  The 
  fraction, 
  at 
  any 
  given 
  time 
  and 
  place, 
  depends 
  

   solely 
  on 
  the 
  zenith 
  distance 
  of 
  the 
  sun, 
  which 
  is 
  continually 
  varying 
  

   with 
  the 
  revolution 
  of 
  the 
  earth. 
  At 
  the 
  equinox, 
  when 
  the 
  sun 
  is 
  

   on 
  the 
  equator, 
  the 
  curve 
  of 
  variation 
  between 
  6 
  a.m. 
  and 
  6 
  p.m. 
  

   is 
  the 
  same 
  as 
  in 
  the 
  other 
  half 
  of 
  the 
  day 
  ; 
  at 
  any 
  other 
  part 
  of 
  

   the 
  year 
  it 
  is 
  not 
  symmetrical 
  in 
  the 
  two 
  halves 
  of 
  the 
  day, 
  but 
  

   is 
  the 
  same 
  during 
  the 
  day 
  in 
  the 
  summer 
  half 
  of 
  the 
  year 
  as 
  during 
  

   the 
  night 
  in 
  the 
  corresponding 
  part 
  of 
  the 
  winter 
  half, 
  when 
  the 
  

   declination 
  of 
  the 
  sun 
  is 
  equal 
  in 
  amount, 
  though 
  opposite 
  in 
  

   direction. 
  

  

  This 
  gave 
  the 
  first 
  suggestion 
  for 
  grouping 
  the 
  records. 
  The 
  

   year 
  was 
  divided 
  into 
  two 
  halves 
  by 
  the 
  equinoxes, 
  and 
  the 
  day 
  

   into 
  two 
  halves 
  at 
  six 
  hours 
  before 
  or 
  after 
  noon, 
  called 
  day 
  and 
  

   night 
  for 
  convenience, 
  irrespective 
  of 
  the 
  time 
  of 
  sunrise 
  or 
  sunset. 
  

   The 
  result 
  is 
  given 
  in 
  the 
  tabular 
  statement 
  below, 
  the 
  frequency 
  

   * 
  Boll. 
  Soc. 
  Sismol. 
  Italiana, 
  vol. 
  xx. 
  (1916) 
  p. 
  30. 
  

  

  