﻿256 
  ANNUAL 
  EEPORT 
  SMITHSONIAN 
  INSTITUTION, 
  1927 
  

  

  earth's 
  radius. 
  This 
  is 
  in 
  the 
  deepest 
  boring, 
  that 
  of 
  Czuchow," 
  in 
  

   upper 
  Silesia, 
  driven 
  by 
  the 
  Prussian 
  Government, 
  purely 
  for 
  the 
  

   solution 
  of 
  important 
  scientific 
  questions. 
  However, 
  the 
  crust 
  fortu- 
  

   nately 
  does 
  not 
  cover 
  the 
  earth 
  as 
  a 
  homogeneous 
  layer. 
  It 
  is 
  broken 
  

   up 
  endlessly 
  into 
  fragments. 
  The 
  separate 
  pieces 
  are 
  multifariously 
  

   and 
  greatly 
  piled 
  upon 
  and 
  against 
  one 
  another. 
  Great 
  masses 
  are 
  

   often 
  folded 
  and 
  thrust 
  into 
  the 
  most 
  complicated 
  patterns. 
  There- 
  

   with 
  is 
  offered 
  to 
  us 
  the 
  possibility 
  of 
  gaining 
  an 
  insight 
  into 
  a 
  con- 
  

   siderably 
  greater 
  depth 
  of 
  the 
  earth's 
  crust. 
  Take, 
  for 
  example, 
  

   northwest 
  Germany. 
  Despite 
  the 
  slight 
  differences 
  in 
  the 
  altitude 
  

   of 
  this 
  region, 
  because 
  of 
  the 
  juxtaposition 
  of 
  portions 
  of 
  the 
  earth's 
  

   crust 
  belonging 
  to 
  very 
  different 
  geological 
  formations 
  and 
  ages, 
  we 
  

   can 
  here 
  inspect 
  an 
  equivalent 
  thickness 
  of 
  12 
  kilometers 
  of 
  sedimen- 
  

   tary 
  rocks, 
  dating 
  from 
  the 
  Devonian 
  to 
  the 
  end 
  of 
  the 
  Cretaceous. 
  

  

  American 
  geologists 
  estimate 
  the 
  possibility 
  of 
  thus 
  gaining 
  an 
  

   insight 
  down 
  to 
  a 
  depth 
  of 
  100 
  or 
  more 
  kilometers 
  of 
  the 
  earth's 
  

   crust. 
  This 
  is 
  surely 
  too 
  large 
  an 
  estimate. 
  It 
  results 
  from 
  a 
  sum- 
  

   mation 
  of 
  the 
  greatest 
  depths 
  estimated 
  from 
  rocks 
  occurring 
  in 
  

   separate 
  regions. 
  The 
  addition 
  of 
  such 
  maximum 
  magnitudes 
  gives 
  

   us 
  a 
  false 
  picture, 
  since 
  in 
  the 
  different 
  regions 
  of 
  the 
  earth, 
  in 
  the 
  

   same 
  geological 
  epoch, 
  under 
  differing 
  geological 
  conditions, 
  quite 
  

   different 
  thicknesses 
  of 
  rocks 
  may 
  have 
  been 
  formed. 
  A 
  depth 
  of 
  

   30 
  kilometers 
  is 
  hardly 
  too 
  small 
  an 
  estimate 
  for 
  the 
  depth 
  of 
  the 
  

   rocks 
  belonging 
  to 
  all 
  the 
  known 
  strata 
  of 
  the 
  earth. 
  Here 
  we 
  

   consider 
  primarily 
  the 
  layers 
  of 
  sedimentary 
  rocks 
  — 
  sandstones, 
  

   limestones, 
  etc. 
  — 
  which 
  occur 
  in 
  numerous 
  modifications 
  due 
  to 
  the 
  

   action 
  of 
  the 
  atmosphere, 
  water, 
  ice, 
  wind, 
  organic 
  life, 
  and 
  which 
  

   form 
  the 
  unique 
  evidences 
  of 
  the 
  earth's 
  history.^ 
  But 
  nowhere 
  is 
  

   this 
  documentary 
  rock 
  book, 
  making 
  up 
  our 
  knowledge 
  of 
  the 
  earth's 
  

   history, 
  complete 
  throughout 
  the 
  30, 
  or 
  let 
  us 
  say 
  100 
  kilometers. 
  

   Nowhere 
  at 
  the 
  surface 
  of 
  the 
  globe 
  have 
  there 
  occurred 
  continuously 
  

   throughout 
  time 
  the 
  formation 
  and 
  conservation 
  of 
  these 
  stratified 
  

   rocks. 
  

  

  The 
  first 
  rock 
  of 
  sedimentary 
  nature 
  could 
  be 
  formed 
  upon 
  the 
  

   earth 
  only 
  when 
  there 
  was 
  already 
  a 
  solid 
  substratum 
  upon 
  which 
  

   and 
  from 
  which 
  sedimentation 
  was 
  made 
  possible. 
  The 
  examination 
  

   of 
  the 
  oldest 
  and 
  deepest 
  known 
  rocks 
  — 
  those 
  of 
  the 
  Archean 
  age 
  — 
  

   shows 
  the 
  simultaneous 
  occurrence 
  of 
  sedimentary 
  as 
  well 
  as 
  igneous 
  

   rocks. 
  The 
  latter 
  exist 
  in 
  such 
  relationship 
  to 
  the 
  sedimentary 
  ones 
  

   that 
  it 
  is 
  indeed 
  impossible 
  that 
  out 
  of 
  these 
  solidified 
  masses 
  the 
  first 
  

  

  ' 
  Czuchow, 
  which 
  was 
  the 
  deepest 
  German 
  and 
  Old 
  World 
  boring, 
  has 
  been 
  surpassed 
  

   by 
  the 
  boring 
  of 
  Prickett's 
  Creek, 
  W. 
  Va., 
  reaching 
  a 
  depth 
  of 
  some 
  40 
  meters 
  more 
  than 
  

   Czuchow. 
  

  

  * 
  F. 
  W. 
  Clarke 
  has 
  computed 
  that 
  the 
  mass 
  of 
  all 
  the 
  sedimentary 
  deposits 
  is 
  sufficient, 
  

   if 
  spread 
  in 
  a 
  layer 
  over 
  the 
  whole 
  earth's 
  surface, 
  to 
  cover 
  the 
  earth 
  only 
  to 
  a 
  depth 
  of 
  

   SOO 
  meters, 
  if 
  we 
  take 
  in 
  consideration 
  a 
  thickness 
  of 
  the 
  earth's 
  crust 
  of 
  16 
  kilometers. 
  

  

  