﻿±68 
  Mr. 
  F. 
  W. 
  Very 
  on 
  the 
  Greenhouse 
  

  

  by 
  those 
  atmospheric 
  constituents 
  which 
  have 
  the 
  first 
  oppor- 
  

   tunity 
  to 
  exercise 
  absorbent 
  action, 
  is 
  used 
  in 
  increasing 
  the 
  

   temperature 
  of 
  the 
  upper 
  air, 
  and 
  is 
  probably 
  responsible 
  for 
  

   a 
  large 
  part 
  of 
  the 
  excess 
  of 
  temperature 
  above 
  that 
  which 
  

   would 
  be 
  indicated 
  by 
  the 
  adiabatic 
  rate, 
  which 
  has 
  been 
  

   made 
  known 
  by 
  the 
  records 
  of 
  sounding 
  balloons. 
  The 
  

   observations 
  of 
  Teisserenc 
  de 
  Bort, 
  who 
  was 
  the 
  first 
  to 
  

   confirm 
  the 
  existence 
  of 
  this 
  hypothetical 
  warm 
  upper 
  layer 
  

   of 
  air, 
  have 
  now 
  been 
  extended 
  by 
  the 
  German 
  sounding- 
  

   balloons 
  to 
  a 
  height 
  of 
  25 
  kilometres, 
  to 
  which 
  height 
  the 
  

   aqueous 
  atmosphere 
  certainly 
  sometimes 
  ascends. 
  Un- 
  

   doubtedly 
  the 
  height 
  of 
  the 
  aqueous 
  atmosphere 
  is 
  a 
  variable 
  

   quantity, 
  subject 
  to 
  wide 
  fluctuations 
  which 
  are 
  partly 
  

   responsible 
  for 
  the 
  variations 
  of 
  surface 
  temperature. 
  In 
  

   summer 
  time, 
  the 
  lower 
  part 
  of 
  the 
  aqueous 
  atmosphere 
  stores 
  

   up 
  a 
  great 
  amount 
  o£ 
  heat, 
  giving 
  hot 
  waves 
  when 
  descending- 
  

   currents 
  prevail 
  during 
  periods 
  of 
  high 
  barometer. 
  In 
  winter, 
  

   on 
  the 
  contrary, 
  the 
  periods 
  of 
  high 
  barometer 
  may 
  be 
  attended 
  

   by 
  cold 
  waves, 
  because 
  the 
  heavily 
  moisture-laden 
  layer 
  in 
  

   immediate 
  contact 
  with 
  the 
  surface 
  is 
  swept 
  away, 
  and 
  surface 
  

   radiation 
  escapes 
  freely; 
  but 
  the 
  cold 
  would 
  theu 
  be 
  far 
  more 
  

   intense 
  if 
  it 
  were 
  not 
  for 
  the 
  presence 
  of 
  the 
  rarer 
  layers 
  of 
  

   the 
  aqueous 
  atmosphere, 
  which 
  still 
  remain 
  as 
  a 
  warm 
  layer 
  

   at 
  no 
  great 
  altitude, 
  but 
  are 
  unable 
  to 
  affect 
  surface 
  tempe- 
  

   ratures 
  much 
  by 
  direct 
  radiation, 
  since 
  the 
  emission 
  of 
  

   radiation 
  by 
  a 
  gas 
  through 
  a 
  deep 
  layer 
  of 
  its 
  own 
  substance 
  

   is 
  small 
  on 
  account 
  of 
  its 
  great 
  absorptive 
  power 
  for 
  its 
  own 
  

   radiation. 
  

  

  The 
  second 
  region 
  of 
  atmospheric 
  heating 
  by 
  absorption 
  of 
  

   radiation 
  is 
  one 
  near 
  the 
  surface 
  where 
  the 
  infra-red 
  radiations 
  

   from 
  either 
  land 
  or 
  water 
  are 
  so 
  thoroughly 
  absorbed 
  at 
  certain 
  

   wave-lengths 
  that 
  these 
  cannot 
  escape 
  except 
  by 
  a 
  slow 
  process 
  

   of 
  absorption 
  and 
  reradiation 
  many 
  times 
  repeated. 
  In 
  this 
  

   respect 
  also, 
  the 
  illustration 
  of 
  the 
  multiple 
  greenhouse 
  is 
  

   again 
  valid, 
  and 
  surface 
  temperatures 
  would 
  accumulate 
  until 
  

   they 
  became 
  unbearable, 
  did 
  not 
  convection 
  overturn 
  the 
  

   atmospheric 
  heat-retaining 
  structure. 
  

  

  The 
  retaining 
  action 
  of 
  an 
  atmosphere 
  for 
  surface 
  heat 
  

   cannot 
  be 
  represented 
  by 
  so 
  simple 
  a 
  device 
  as 
  that 
  of 
  a 
  thin 
  

   sheet 
  of 
  perfectly 
  conducting 
  glass, 
  having 
  the 
  same 
  tempe- 
  

   rature 
  at 
  its 
  upper 
  and 
  lower 
  surfaces. 
  It 
  seems 
  to 
  me 
  that 
  

   in 
  part 
  Professor 
  Poynting's 
  argument 
  is 
  irrelevant 
  as 
  regards 
  

   the 
  problem 
  of 
  the 
  surface 
  temperature 
  of 
  a 
  planet 
  without 
  

   the 
  inclusion 
  of 
  further 
  details. 
  If 
  Professor 
  Poynting 
  will 
  

   turn 
  his 
  great 
  mathematical 
  ability 
  to 
  the 
  consideration 
  of 
  

   some 
  of 
  the 
  numerous 
  alternative 
  hypotheses, 
  it 
  seems 
  pro- 
  

  

  