﻿X-RAYING 
  THE 
  EARTH 
  

  

  By 
  Reginald 
  A. 
  Daly 
  

  

  Reality 
  is 
  never 
  skin-deep. 
  The 
  true 
  nature 
  of 
  the 
  earth 
  and 
  its 
  

   full 
  wealth 
  of 
  hidden 
  treasures 
  can 
  not 
  be 
  argued 
  from 
  the 
  visible 
  

   rocks, 
  the 
  rocks 
  upon 
  which 
  we 
  live 
  and 
  out 
  of 
  which 
  we 
  make 
  our 
  

   living. 
  The 
  face 
  of 
  the 
  earth, 
  with 
  its 
  upstanding 
  continents 
  and 
  

   depressed 
  ocean 
  deeps, 
  its 
  vast 
  ornament 
  of 
  plateau 
  and 
  mountain 
  

   chain, 
  is 
  molded 
  by 
  structure 
  and 
  process 
  in 
  hidden 
  depths. 
  

  

  During 
  the 
  nineteenth 
  century 
  the 
  geologists, 
  a 
  mere 
  handful 
  among 
  

   the 
  world's 
  workers, 
  studied 
  the 
  rocks 
  at 
  the 
  surface, 
  the 
  accessible 
  

   skin 
  of 
  the 
  globe. 
  They 
  established 
  many 
  principal 
  points 
  in 
  our 
  

   planet's 
  history. 
  While 
  with 
  the 
  astronomers 
  space 
  was 
  deepening, 
  

   a 
  million 
  years 
  became 
  for 
  the 
  rock 
  men 
  the 
  unit 
  of 
  time 
  with 
  which 
  

   to 
  outline" 
  earth's 
  dramatic 
  story. 
  Thus, 
  incidentally, 
  the 
  way 
  was 
  

   opened 
  for 
  the 
  doctrine 
  of 
  organic 
  evolution, 
  demanding 
  hundreds 
  of 
  

   millions 
  of 
  years, 
  to 
  become 
  secured 
  science 
  rather 
  than 
  mere 
  specula- 
  

   tion. 
  The 
  first, 
  main 
  jobs 
  of 
  the 
  geologist 
  were 
  to 
  map 
  the 
  exposures 
  

   of 
  the 
  rocks 
  at 
  the 
  surface 
  of 
  the 
  earth's 
  skin 
  or 
  "crust," 
  to 
  distinguish 
  

   the 
  kinds 
  and 
  relative 
  ages 
  of 
  the 
  rocks, 
  and, 
  in 
  general, 
  to 
  gather 
  

   the 
  many 
  facts 
  that 
  must 
  be 
  accounted 
  for 
  in 
  the 
  final 
  explanation 
  

   of 
  continent, 
  ocean, 
  plateau, 
  and 
  mountain 
  range. 
  Yet 
  the 
  century 
  

   closed 
  without 
  having 
  revealed 
  definite 
  origins 
  for 
  these 
  and 
  for 
  

   many 
  smaller 
  details 
  of 
  the 
  earth's 
  surface 
  and 
  "crust." 
  With 
  in- 
  

   creasing 
  clearness 
  geologists 
  became 
  convinced, 
  however, 
  that 
  the 
  

   main 
  secret 
  of 
  highland 
  and 
  lowland, 
  dry 
  land 
  and 
  deep 
  ocean, 
  

   Himalaya 
  and 
  Mediterranean, 
  barren 
  rock 
  and 
  ore-bearing 
  rock, 
  

   must 
  be 
  sought 
  in 
  the 
  invisible, 
  the 
  deep 
  underground 
  of 
  the 
  earth. 
  

  

  The 
  nineteenth 
  century 
  bequeathed 
  to 
  the 
  twentieth 
  an 
  outstand- 
  

   ing 
  responsibility 
  — 
  to 
  invent 
  and 
  use 
  new 
  methods 
  of 
  exploring 
  the 
  

   earth's 
  body 
  far 
  beyond 
  the 
  reach 
  of 
  direct 
  penetration 
  by 
  the 
  geol- 
  

   ogist's 
  eye 
  or 
  by 
  mine 
  and 
  bore 
  hole. 
  What 
  is 
  the 
  nature 
  of 
  the 
  

   materials 
  below 
  the 
  visible 
  rocks? 
  How 
  are 
  those 
  materials 
  arranged? 
  

   What 
  energies 
  are 
  stored 
  in 
  the 
  globe, 
  ready 
  to 
  do 
  geological 
  work 
  

   when 
  the 
  occasion 
  comes? 
  Where 
  is 
  the 
  earth's 
  body 
  strong, 
  truly 
  

  

  ' 
  Reprinted 
  by 
  permission 
  from 
  the 
  Harvard 
  Alumni 
  Bulletin, 
  Oct. 
  18, 
  1928. 
  

  

  261 
  

  

  