﻿264 
  ANNUAL 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  192 
  9 
  

  

  vibrating 
  rock 
  and 
  give 
  a 
  written 
  record, 
  or 
  "graph," 
  of 
  that 
  motion. 
  

   They 
  form 
  the 
  main 
  equipment 
  of 
  seismographic 
  stations. 
  The 
  

   mechanical 
  or 
  photographic 
  record 
  of 
  a 
  distant 
  shock 
  is 
  the 
  seismo- 
  

   gram, 
  a 
  kind 
  of 
  hieroglyphic 
  message 
  from 
  the 
  mysterious 
  heart 
  of 
  the 
  

   planet. 
  Each 
  seismogram 
  from 
  a 
  strong 
  earthquake 
  is 
  a 
  long, 
  com- 
  

   plex 
  curve 
  traced 
  up 
  and 
  down 
  on 
  the 
  registering 
  paper 
  of 
  the 
  seis- 
  

   mograph. 
  Usually 
  the 
  impulses 
  of 
  the 
  longitudinal 
  and 
  transverse 
  

   waves 
  are 
  evident 
  to 
  the 
  expert 
  seismologist, 
  but 
  in 
  every 
  case 
  he 
  

   finds 
  represented 
  much 
  more 
  than 
  these 
  two 
  simple 
  kinds 
  of 
  motion. 
  

   He 
  sees, 
  in 
  fact, 
  a 
  whole 
  train 
  of 
  waves, 
  which 
  came 
  racing 
  out 
  of 
  the 
  

   earth, 
  often 
  for 
  much 
  more 
  than 
  an 
  hour 
  after 
  the 
  first 
  impulse 
  was 
  

   registered. 
  A 
  generation 
  ago, 
  most 
  of 
  the 
  complex 
  message 
  could 
  not 
  

   be 
  read. 
  Then 
  seismologists 
  bethought 
  themselves 
  of 
  a 
  Rosetta 
  

   stone. 
  

  

  Observation 
  and 
  theorj'" 
  soon 
  showed 
  that 
  earthquake 
  waves 
  are 
  

   closely 
  analogous 
  to 
  the 
  familiar 
  waves 
  of 
  soiyid 
  and 
  light. 
  Like 
  

   these, 
  the 
  seismic 
  rays 
  are 
  reflected 
  and 
  refracted 
  at 
  surfaces 
  between 
  

   different 
  kinds 
  of 
  material. 
  Seismic 
  rays, 
  during 
  their 
  passage 
  through 
  

   the 
  earth, 
  are 
  broken 
  up 
  and 
  dispersed, 
  just 
  as 
  the 
  sun's 
  light 
  is 
  

   dispersed, 
  in 
  prism 
  or 
  rain 
  drop, 
  to 
  make 
  the 
  glory 
  of 
  the 
  rainbow. 
  

   Seismic 
  rays 
  are 
  diffracted, 
  just 
  as 
  light 
  rays 
  are 
  diffracted, 
  at 
  the 
  

   interfaces 
  of 
  contrasted 
  materials. 
  As 
  sound 
  travels 
  faster 
  in 
  water 
  

   than 
  in 
  air, 
  faster 
  in 
  rock 
  than 
  in 
  either, 
  so 
  seismic 
  waves 
  travel 
  faster 
  

   in 
  some 
  kinds 
  of 
  rock 
  than 
  in 
  other 
  kinds. 
  Long 
  study 
  of 
  sound 
  and 
  

   light 
  has 
  led 
  to 
  the 
  discovery 
  of 
  the 
  laws 
  of 
  wave 
  motion, 
  and 
  these 
  

   have 
  made 
  increasingly 
  clear 
  the 
  meaning 
  of 
  seismograms. 
  The 
  

   analogy 
  with 
  sound 
  and 
  light 
  is 
  the 
  Rosetta 
  stone. 
  

  

  The 
  discovery 
  of 
  the 
  famous 
  original 
  enabled 
  Napoleon's 
  experts 
  to 
  

   begin 
  the 
  reading 
  of 
  Egypt's 
  ancient 
  literature. 
  In 
  like 
  manner 
  the 
  

   seismologists, 
  using 
  the 
  difficult 
  but 
  manageable 
  Greek 
  of 
  modern 
  

   physics, 
  are 
  beginning 
  the 
  task 
  of 
  making 
  earthquakes 
  tell 
  the 
  nature 
  

   of 
  the 
  earth's 
  interior 
  and 
  translating 
  into 
  significant 
  speech 
  the 
  

   hieroglypliics 
  written 
  by 
  the 
  seismograph. 
  It 
  is 
  a 
  long 
  task, 
  requiring 
  

   high 
  intelligence 
  and 
  the 
  patient 
  accumulation 
  of 
  earthquake 
  data 
  

   from 
  aU 
  parts 
  of 
  the 
  globe, 
  from 
  ocean 
  basin 
  as 
  well 
  as 
  from 
  continent. 
  

   The 
  work 
  is 
  only 
  just 
  begun; 
  yet 
  the 
  results 
  already 
  obtained 
  are 
  of 
  

   supreme 
  interest 
  to 
  the 
  philosopher, 
  to 
  the 
  geologist, 
  and 
  to 
  the 
  pro- 
  

   ducer 
  of 
  petroleum, 
  metals, 
  and 
  other 
  materials 
  from 
  the 
  rocks. 
  

  

  For 
  here, 
  too, 
  the 
  man 
  of 
  pure 
  science, 
  the 
  seismologist, 
  "fussing 
  

   with 
  experiments 
  of 
  no 
  use 
  to 
  anyone," 
  has 
  proved 
  to 
  be 
  another 
  

   goose 
  that 
  has 
  laid 
  a 
  golden 
  egg. 
  The 
  methods 
  developed 
  by 
  the 
  

   worker 
  in 
  another 
  "pure" 
  science, 
  seismology, 
  are 
  now, 
  with 
  the 
  help 
  

   of 
  artificial 
  earthquakes, 
  locating 
  structures 
  that 
  lead 
  to 
  hidden 
  deposits 
  

   of 
  oU. 
  So, 
  millions 
  are 
  to 
  be 
  saved 
  in 
  the 
  cost 
  of 
  bore 
  holes, 
  and 
  new 
  

   oil, 
  probably 
  by 
  the 
  hundreds 
  of 
  millions 
  of 
  barrels, 
  will 
  be 
  added 
  to 
  

  

  