﻿134 
  Johnston 
  — 
  Temperature 
  in 
  Deep 
  Wells 
  at 
  Findlay. 
  

  

  The 
  actual 
  results 
  are 
  presented 
  in 
  the 
  above 
  table. 
  The 
  

   depths 
  were 
  determined 
  by 
  measuring 
  down 
  the 
  sand 
  line, 
  a 
  

   method 
  which 
  is 
  of 
  ample 
  accuracy 
  for 
  the 
  present 
  purpose. 
  

   The 
  first 
  trial 
  was 
  made 
  at 
  a 
  depth 
  of 
  1165 
  feet, 
  the' 
  ther- 
  

   mometers 
  being 
  left 
  at 
  that 
  level 
  for 
  one 
  and 
  one 
  -half 
  hours, 
  and 
  

   in 
  a 
  second 
  trial 
  for 
  one 
  hour 
  only 
  ; 
  the 
  concordance 
  of 
  the 
  

   results 
  thus 
  obtained 
  shows 
  that, 
  with 
  the 
  form 
  of 
  apparatus 
  

   used,* 
  a 
  period 
  of 
  one 
  and 
  one-quarter 
  hours 
  sufficed 
  substan- 
  

   tially 
  for 
  the 
  attainment 
  by 
  the 
  thermometers 
  of 
  the 
  tempera- 
  

   ture 
  of 
  the 
  zone 
  in 
  which 
  they 
  were 
  placed. 
  This 
  is 
  confirmed 
  

   by 
  the 
  agreement 
  between 
  the 
  'measurements 
  made 
  with 
  a 
  

   period 
  of 
  one 
  and 
  one-quarter 
  to 
  one 
  and 
  one-half 
  hours 
  and 
  

   those 
  in 
  which 
  the 
  thermometers 
  were 
  left 
  overnight 
  in 
  the 
  

   hole 
  ; 
  as 
  is 
  evident 
  from 
  the 
  figure, 
  in 
  which 
  temperatures 
  

   have 
  been 
  plotted 
  against 
  depths. 
  

  

  The 
  figure 
  shows 
  very 
  plainly 
  the 
  general 
  regularity 
  of 
  the 
  

   results, 
  apart 
  from 
  the 
  marked 
  discontinuity 
  which 
  was 
  

   observed, 
  as 
  might 
  be 
  expected, 
  at 
  the 
  point 
  at 
  which 
  gas 
  

   appears. 
  The 
  temperatures 
  observed 
  at 
  depths 
  less 
  than 
  770 
  

   feet 
  do 
  not 
  represent 
  the 
  temperature 
  of 
  the 
  surrounding 
  rock, 
  

   but 
  that 
  of 
  the 
  atmosphere 
  in 
  the 
  -well, 
  which 
  is 
  cooled 
  by 
  the 
  

   flow 
  of 
  gas 
  between 
  the 
  outer 
  and 
  inner 
  casing 
  of 
  the 
  well. 
  

   The 
  temperature 
  gradient 
  in 
  the 
  sedimentary 
  rocks 
  from 
  the 
  

   "Trenton" 
  limestone 
  downward 
  is 
  about 
  041°C. 
  (0-74° 
  F.) 
  

   per 
  100 
  feet 
  ; 
  that 
  in 
  the 
  crystalline 
  rocks 
  appears 
  to 
  be 
  some- 
  

   what 
  higher, 
  but 
  the 
  data 
  are 
  insufficient 
  to 
  enable 
  one 
  to 
  draw 
  

   any 
  very 
  certain 
  conclusions 
  from 
  this 
  phenomenon. 
  

  

  Geophysical 
  Laboratory, 
  

  

  Carnegie 
  Institution 
  of 
  Washington, 
  

   Washington, 
  D. 
  C, 
  June, 
  1913. 
  

  

  * 
  The 
  period 
  required 
  for 
  the 
  practical 
  attainment 
  of 
  temperature 
  equili- 
  

   brium 
  between 
  thermometers 
  and 
  the 
  surrounding 
  rock 
  depends 
  of 
  course 
  

   upon 
  the 
  form 
  and 
  weight 
  of 
  the 
  cage 
  surrounding 
  the 
  thermometers 
  and 
  

   should 
  always 
  be 
  determined 
  by 
  actual 
  trial. 
  

  

  