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  depth 
  as 
  the 
  thickness 
  of 
  the 
  underlying 
  coal 
  vein 
  is 
  the 
  result. 
  

   When 
  the 
  seam 
  is 
  deeper 
  underground 
  the 
  effect 
  may 
  be 
  merely 
  a 
  

   crack 
  with 
  a 
  slight 
  settling. 
  It 
  is 
  reported 
  that 
  this 
  cracking 
  of 
  the 
  

   surface 
  has 
  taken 
  place 
  when 
  the 
  coal 
  lay 
  at 
  a 
  depth 
  of 
  300 
  to 
  500 
  

   feet. 
  In 
  localities 
  where 
  the 
  coal 
  lies 
  in 
  general 
  50 
  to 
  100 
  feet 
  below 
  

   the 
  surface 
  the 
  lower 
  margin 
  of 
  a 
  hill 
  may 
  have 
  a 
  belt 
  of 
  sink 
  holes 
  

   due 
  to 
  mining 
  and 
  the 
  upper 
  portion 
  of 
  the 
  hill 
  remain 
  unbroken, 
  

   though 
  occasionally 
  cracked. 
  

  

  Breaking 
  or 
  cracking 
  of 
  the 
  surface 
  lowers 
  the 
  permanent 
  water 
  

   level 
  to 
  the 
  mine. 
  Local 
  wells 
  and 
  springs 
  run 
  dry, 
  and 
  small 
  

   streams 
  sometimes 
  disappear. 
  On 
  such 
  situations 
  older 
  trees 
  die 
  as 
  

   a 
  result 
  of 
  the 
  change 
  in 
  drainage 
  conditions, 
  but 
  young 
  sprouts 
  and 
  

   seedlings 
  adapt 
  themselves 
  to 
  the 
  new 
  conditions. 
  Heavy 
  soil 
  that 
  

   was 
  formerly 
  poorly 
  drained 
  has 
  sometimes 
  been 
  improved 
  by 
  the 
  

   increased 
  drainage 
  in 
  the 
  same 
  way 
  that 
  tile 
  draining 
  improves 
  

   similar 
  land 
  elsewhere. 
  Areas 
  where 
  there 
  are 
  many 
  sink 
  holes 
  are, 
  

   however, 
  comparatively 
  valueless 
  for 
  agriculture. 
  

  

  EFFECT 
  OF 
  COKE 
  PRODUCTION. 
  

  

  A 
  large 
  amount 
  of 
  coal 
  mined 
  in 
  western 
  Pennsylvania 
  is 
  used 
  at 
  

   the 
  mines 
  to 
  make 
  coke 
  to 
  be 
  shipped 
  for 
  use 
  at 
  iron 
  and 
  steel 
  mills. 
  

   The 
  manufacture 
  of 
  this 
  product 
  destroys 
  the 
  existing 
  timber 
  and 
  

   prevents 
  forest 
  planting 
  in 
  the 
  immediate 
  vicinity 
  of 
  the 
  works, 
  

   because 
  the 
  fumes 
  from 
  the 
  coke 
  ovens 
  contain 
  sulphur 
  gas, 
  which 
  

   causes 
  the 
  death 
  of 
  all 
  vegetation 
  subjected 
  to 
  a 
  continuous 
  draft 
  of 
  

   this 
  smoke. 
  The 
  action 
  of 
  the 
  sulphur 
  gas 
  on 
  the 
  leaves 
  is 
  corrosive. 
  

  

  Much 
  land 
  is 
  protected 
  on 
  account 
  of 
  the 
  hilly 
  character 
  of 
  this 
  

   region. 
  If 
  the 
  ovens 
  are 
  situated 
  at 
  the 
  base 
  of 
  a 
  hill 
  against 
  which 
  

   the 
  prevailing 
  wind 
  carries 
  the 
  smoke, 
  the 
  hillside 
  soon 
  becomes 
  

   bare 
  of 
  vegetation, 
  but 
  on 
  the 
  opposite 
  side 
  of 
  the 
  hill 
  crops 
  may 
  be 
  

   grown 
  nearly 
  to 
  the 
  top. 
  The 
  injurious 
  effect 
  of 
  the 
  smoke 
  is 
  notice- 
  

   able, 
  however, 
  at 
  a 
  greater 
  distance 
  in 
  those 
  situations 
  where 
  the 
  

   wind 
  carries 
  the 
  smoke 
  up 
  a 
  small, 
  narrow 
  valley. 
  Crops 
  several 
  

   miles 
  away 
  are 
  often 
  blackened, 
  but 
  do 
  not 
  seem 
  to 
  be 
  injured. 
  

   The 
  death 
  of 
  orchards 
  and 
  forest 
  trees, 
  caused 
  by 
  the 
  changed 
  con- 
  

   ditions 
  of 
  drainage 
  already 
  described, 
  is 
  frequently 
  attributed 
  to 
  

   the 
  action 
  of 
  coke 
  smoke. 
  

  

  In 
  some 
  instances 
  by-product 
  ovens 
  have 
  been 
  established 
  which 
  

   collect 
  and 
  condense 
  the 
  sulphur 
  gas 
  to 
  make 
  commercial 
  sulphuric 
  

   acid. 
  

  

  OPPORTUNITY 
  FOR 
  FOREST 
  PLANTING. 
  

  

  The 
  occasion 
  for 
  forest 
  planting 
  rests 
  primarily 
  upon 
  the 
  growing 
  

   need 
  of 
  pit 
  props, 
  and 
  is 
  intimately 
  related 
  to 
  the 
  whole 
  industrial 
  

   development 
  of 
  southwestern 
  Pennsylvania. 
  

  

  