﻿F. 
  W. 
  Very— 
  Solar 
  Badiation. 
  617 
  

  

  the 
  exterior 
  of 
  the 
  planet, 
  but 
  on 
  that 
  which 
  penetrates 
  to 
  the 
  

   earth's 
  surface, 
  chiefly 
  the 
  land 
  surface 
  of 
  the 
  globe. 
  The 
  

   greater 
  part 
  of 
  the 
  earth's 
  surface 
  being, 
  however, 
  one 
  of 
  

   water, 
  the 
  principal 
  immediate 
  effect 
  of 
  the 
  increased 
  heat 
  

   must 
  be 
  to 
  increase 
  the 
  evaporation, 
  and 
  therefore, 
  as 
  a 
  subse- 
  

   quent 
  process, 
  the 
  cloud 
  and 
  the 
  rainfall. 
  Now 
  a 
  cloudy 
  

   atmosphere 
  intercepts 
  a 
  great 
  part 
  of 
  the 
  solar 
  heat 
  ; 
  and 
  the 
  

   re-evaporation 
  of 
  the 
  fallen 
  rain 
  lowers 
  the 
  temperature 
  of 
  the 
  

   surface 
  from 
  which 
  it 
  evaporates, 
  and 
  that 
  of 
  the 
  stratum 
  of 
  

   air 
  in 
  contact 
  with 
  it. 
  The 
  heat 
  liberated 
  by 
  cloud 
  condensa- 
  

   tion 
  doubtless 
  raises 
  the 
  temperature 
  of 
  the 
  air 
  at 
  the 
  altitude 
  

   of 
  the 
  cloudy 
  stratum, 
  but 
  this 
  is 
  not 
  recorded 
  in 
  our 
  registers. 
  

   As 
  a 
  consequence, 
  an 
  increased 
  formation 
  of 
  vapor, 
  and 
  there- 
  

   fore 
  of 
  rain, 
  following 
  on 
  an 
  increase 
  of 
  radiation, 
  might 
  be 
  

   expected 
  to 
  coincide 
  with 
  a 
  low 
  air-temperature 
  on 
  the 
  surface 
  

   of 
  the 
  land."* 
  This 
  explanation 
  does 
  not 
  exclude 
  the 
  one 
  which 
  

   I 
  have 
  suggested, 
  but 
  is 
  to 
  be 
  looked 
  upon 
  as 
  an 
  additional 
  

   cause 
  of 
  local 
  discrepancies 
  which 
  do 
  not 
  invalidate 
  the 
  wider 
  

   conception 
  which 
  includes 
  them. 
  Mr. 
  Elanford 
  refers 
  to 
  his 
  

   explanation 
  as 
  a 
  " 
  speculation 
  ... 
  in 
  part 
  suggested 
  by 
  the 
  

   discovery 
  of 
  Messrs. 
  Meldrum 
  and 
  Lockyer 
  that 
  the 
  frequency 
  

   and 
  energy 
  of 
  cyclones 
  and 
  the 
  rainfall 
  of 
  the 
  globe 
  appear 
  to 
  

   vary 
  directly 
  as 
  the 
  abundance 
  of 
  sun-spots." 
  

  

  It 
  will 
  be 
  seen 
  that 
  in 
  this 
  case, 
  as 
  in 
  some 
  others, 
  Mr. 
  

   Abbot 
  has 
  included 
  only 
  one 
  side 
  of 
  a 
  controverted 
  subject 
  in 
  

   his 
  treatise. 
  In 
  more 
  than 
  one 
  place 
  he 
  also 
  cites 
  as 
  authorities 
  

   for 
  his 
  statements 
  names 
  of 
  investigators 
  who 
  have 
  held 
  diverse 
  

   opinions. 
  Mention 
  is 
  madef 
  of 
  the 
  shifting 
  of 
  the 
  zones 
  of 
  

   maximum 
  frequency 
  of 
  prominences, 
  but 
  no 
  notice 
  is 
  taken 
  of 
  

   the 
  short 
  period 
  of 
  this 
  shift 
  (3 
  to 
  4 
  years) 
  which 
  is 
  shown 
  by 
  

   Lockyer's 
  curves 
  for 
  solar 
  latitudes 
  30° 
  to 
  60°. 
  Bigelow 
  finds 
  

   that 
  this 
  shift 
  synchronizes 
  with 
  a 
  periodic 
  change 
  in 
  terres- 
  

   trial 
  climates 
  which 
  is 
  even 
  more 
  marked 
  than 
  the 
  11-year 
  

   cycle. 
  He 
  says 
  : 
  " 
  The 
  frequency 
  variation 
  of 
  the 
  solar 
  prom- 
  

   inences 
  in 
  the 
  higher 
  latitudes 
  gives 
  the 
  key 
  that 
  was 
  wanted 
  

   to 
  enable 
  us 
  to 
  study 
  the 
  meteorological 
  conditions 
  in 
  the 
  

   earth's 
  atmosphere 
  with 
  some 
  prospect 
  of 
  success. 
  This 
  varia- 
  

   tion 
  shows 
  that 
  the 
  meteorological 
  pulse 
  is 
  registered 
  most 
  

   favorably 
  not 
  in 
  the 
  sun-spot 
  belts, 
  but 
  in 
  the 
  zones 
  of 
  the 
  sun 
  

   corresponding 
  with 
  the 
  temperate 
  zones 
  of 
  the 
  earth 
  from 
  lati- 
  

   tude 
  30° 
  to 
  60°."t 
  

  

  Owing 
  to 
  the 
  periodic 
  interchange 
  of 
  climatic 
  conditions 
  

   over 
  extensive 
  areas 
  of 
  the 
  earth's 
  surface, 
  we 
  have 
  the 
  phe- 
  

  

  * 
  Astrophysical 
  Journal, 
  vol. 
  vii, 
  p. 
  159-160. 
  

   t 
  The 
  Sun, 
  p. 
  195. 
  

  

  % 
  Frank 
  H. 
  Bigelow 
  : 
  " 
  Studies 
  on 
  the 
  Diurnal 
  Periods 
  in 
  the 
  Lower 
  Strata 
  

   of 
  the 
  Atmosphere," 
  p. 
  41. 
  U. 
  S. 
  Weather 
  Bureau, 
  1905. 
  

  

  