﻿Geology 
  and 
  Mineralogy. 
  171 
  

  

  gists, 
  viz., 
  do 
  the 
  adjustments 
  of 
  level 
  initiate 
  cycles 
  of 
  erosion 
  

   and 
  determine 
  the 
  locations 
  of 
  areas 
  of 
  denudation 
  and 
  of 
  deposi- 
  

   tion, 
  or 
  do 
  adjustments 
  of 
  level 
  result 
  from 
  shifting 
  of 
  load 
  by 
  

   streams 
  and 
  other 
  transporting 
  agents 
  ? 
  

  

  In 
  a 
  problem 
  involving 
  a 
  large 
  number 
  of 
  unknown 
  factors 
  any 
  

   new 
  line 
  of 
  investigation 
  is 
  welcome, 
  and 
  for 
  this 
  reason 
  the 
  

   experiments 
  being 
  conducted 
  in 
  New 
  South 
  Wales 
  assume 
  high 
  

   value. 
  It 
  was 
  my 
  good 
  fortune 
  to 
  see 
  the 
  geologic 
  features 
  along 
  

   a 
  40-mile 
  stretch 
  of 
  the 
  Murrumbidgee 
  and 
  to 
  note 
  the 
  methods 
  

   adopted 
  for 
  this 
  line 
  of 
  investigations. 
  

  

  The 
  Burrinjuck 
  dam 
  on 
  the 
  Murrumbidgee 
  River, 
  now 
  nearing 
  

   completion, 
  is 
  a 
  rival 
  of 
  the 
  Roosevelt 
  dam 
  of 
  Arizona, 
  which 
  it 
  

   resembles 
  in 
  form 
  and 
  geological 
  setting. 
  The 
  dam, 
  240 
  feet 
  

   high, 
  will 
  form 
  a 
  lake 
  41 
  miles 
  long, 
  holding 
  33,000,000,000 
  cubic 
  

   feet, 
  1,031,250,000 
  tons 
  of 
  water, 
  equal 
  in 
  weight 
  to 
  amass 
  of 
  

   sand 
  and 
  gravel 
  2 
  miles 
  long, 
  1 
  mile 
  wide, 
  322 
  feet 
  deep. 
  If 
  the 
  

   earth's 
  crust 
  is 
  sufficiently 
  elastic 
  or 
  plastic 
  to 
  yield 
  in 
  response 
  to 
  

   a 
  load 
  of 
  such 
  weight 
  and 
  dimensions, 
  it 
  should 
  be 
  possible 
  to 
  

   record 
  the 
  fact 
  with 
  suitable 
  instruments. 
  Acting 
  on 
  the 
  sugges- 
  

   tion 
  of 
  Dr. 
  W. 
  G. 
  Woolnough, 
  three 
  seismographs 
  were 
  obtained, 
  

   two 
  of 
  the 
  Rebeur-Ehlert 
  type, 
  previously 
  used 
  by 
  Hecker 
  and 
  

   Schweydar 
  in 
  the 
  investigation 
  of 
  earth 
  tides, 
  and 
  one 
  of 
  the 
  

   Zollner 
  suspension 
  type 
  designed 
  by 
  Hecker. 
  Careful 
  considera- 
  

   tion 
  was 
  given 
  to 
  the 
  selection 
  of 
  sites 
  by 
  David 
  and 
  Cotton, 
  

   geologists 
  ; 
  Father 
  Pigot, 
  seismologist 
  ; 
  and 
  D. 
  F. 
  Campbell, 
  resi- 
  

   dent 
  engineer. 
  The 
  geologic 
  conditions 
  were 
  kept 
  in 
  mind 
  and 
  

   elaborate 
  precautions 
  were 
  taken 
  in 
  the 
  installation 
  of 
  instruments. 
  

   Tunnels 
  60 
  to 
  80 
  feet 
  long 
  were 
  excavated 
  in 
  rock 
  and 
  the 
  pendu- 
  

   lums 
  placed 
  in 
  the 
  innermost 
  of 
  three 
  compartments, 
  the 
  second 
  

   of 
  which 
  contains 
  the 
  recording 
  apparatus. 
  The 
  instruments 
  

   were 
  first 
  used 
  to 
  supplement 
  geologic 
  investigations 
  on 
  the 
  

   normal 
  stability 
  of 
  the 
  earth's 
  crust 
  at 
  Burrinjuck. 
  The 
  pendu- 
  

   lums 
  are 
  recording 
  four 
  types 
  of 
  movements 
  : 
  earthtides, 
  which 
  

   will 
  be 
  compared 
  with 
  those 
  recorded 
  on 
  the 
  instrument 
  of 
  the 
  

   International 
  Geodetic 
  Association 
  at 
  Cobar, 
  360 
  miles 
  from 
  the 
  

   coast 
  (Burrinjuck 
  is 
  125 
  miles 
  from 
  the 
  sea) 
  ; 
  earthquakes 
  ; 
  fault 
  

   movements 
  ; 
  slow 
  deflections 
  from 
  the 
  vertical. 
  This 
  last 
  type 
  of 
  

   movements 
  " 
  may 
  be 
  related 
  chiefly 
  to 
  the 
  water 
  loads 
  or 
  may 
  be 
  

   due 
  to 
  other 
  causes, 
  but 
  it 
  seems 
  almost 
  certain 
  that 
  the 
  former 
  

   cause 
  is 
  in 
  operation." 
  The 
  results 
  of 
  the 
  experiments 
  so 
  far 
  car- 
  

   ried 
  out 
  look 
  toward 
  a 
  conclusion 
  that 
  either 
  elastic 
  yielding 
  or 
  iso- 
  

   static 
  adjustment 
  affects 
  areas 
  as 
  small 
  as 
  a 
  few 
  square 
  miles. 
  

   Cotton 
  raises 
  the 
  pertinent 
  question 
  as 
  to 
  whether 
  the 
  extremely 
  

   contrasted 
  views 
  of 
  Barrell 
  and 
  Hobbs 
  on 
  the 
  one 
  hand 
  and 
  of 
  

   Hayford 
  and 
  Bowie 
  on 
  the 
  other 
  hand 
  may 
  not 
  be 
  reconciled 
  on 
  

   the 
  basis 
  of 
  the 
  stability 
  of 
  a 
  given 
  area 
  prior 
  to 
  the 
  removal 
  or 
  

   deposition 
  of 
  a 
  load. 
  

  

  Further 
  reports 
  on 
  the 
  Burrinjuck 
  experiments 
  will 
  be 
  awaited 
  

   with 
  interest, 
  and 
  it 
  is 
  highly 
  desirable 
  that 
  similar 
  investigations 
  

   be 
  undertaken 
  within 
  the 
  United 
  States. 
  h. 
  e. 
  g. 
  

  

  