﻿580 
  Messrs. 
  H. 
  E. 
  Roscoe 
  and 
  B. 
  Stewart 
  on 
  [June 
  17,, 
  

  

  Let 
  us 
  now 
  endeavour 
  to 
  compare 
  the 
  heat 
  of 
  sunshine 
  between 
  the 
  

   winter 
  solstice 
  and 
  the 
  ensuing 
  summer 
  solstice 
  with 
  that 
  between 
  the 
  

   summer 
  solstice 
  and 
  the 
  ensuing 
  winter 
  solstice. 
  The 
  results 
  of 
  this 
  

   comparison 
  are 
  given 
  in 
  the 
  following 
  Table 
  : 
  — 
  

  

  Table 
  II. 
  

  

  Comparing 
  the 
  heat 
  of 
  sunshine 
  during 
  the 
  six 
  months 
  preceding 
  the 
  

   summer 
  solstice 
  with 
  its 
  heat 
  during 
  the 
  six 
  months 
  following 
  the 
  same. 
  

  

  

  Heat 
  of 
  the 
  Sun 
  during 
  the 
  

  

  Year. 
  

  

  six 
  months 
  

  

  

  

  

  x 
  receding 
  

  

  _r 
  oilo'wing 
  

  

  

  solstice. 
  

  

  solstice. 
  

  

  1 
  ft 
  

  

  7*808 
  

  

  3-450 
  

  

  

  1-095 
  

  

  1-223 
  

  

  1 
  ft^T 
  

  

  1-093 
  

  

  0-445 
  

  

  1 
  

  

  19*484 
  

  

  22-954 
  

  

  1 
  Q^O 
  

  

  zO-ooo 
  

  

  oU 
  obo 
  

  

  1 
  ftftfi 
  

  

  12*990 
  

  

  19*433 
  

  

  1861...... 
  

  

  ±\J 
  OoO 
  

  

  

  1862 
  

  

  8-624 
  

  

  20-885 
  

  

  1863...... 
  

  

  5-910 
  

  

  24*205 
  

  

  1864. 
  

  

  4-120 
  

  

  15-138 
  

  

  1865 
  

  

  10-071 
  

  

  18-040 
  

  

  1866. 
  

  

  6-785 
  

  

  19-005 
  

  

  1867 
  

  

  9-785 
  

  

  23-460 
  

  

  1868 
  

  

  15-435 
  

  

  13-755 
  

  

  1869 
  

  

  6-770 
  

  

  24-443 
  

  

  1870 
  

  

  9-750 
  

  

  22-000 
  

  

  1871 
  

  

  15-680 
  

  

  16-785 
  

  

  1872...... 
  

  

  5-170 
  

  

  14*505 
  

  

  1873 
  

  

  3-653 
  

  

  25-538 
  

  

  1874 
  

  

  8-905 
  

  

  20-573 
  

  

  

  184*174 
  

  

  353-680 
  

  

  Prom 
  this 
  table 
  it 
  appears, 
  as 
  might 
  be 
  expected, 
  that 
  the 
  heat 
  of 
  

   sunshine 
  is 
  greater 
  during 
  the 
  second 
  than 
  during 
  the 
  first 
  half 
  of 
  the 
  

   year, 
  reckoning 
  from 
  the 
  sum 
  mer 
  solstice 
  ; 
  and 
  this 
  result 
  is 
  borne 
  out 
  by 
  

   the 
  observations 
  made 
  by 
  one 
  of 
  us* 
  that 
  the 
  chemically 
  active 
  solar 
  rays 
  

   are 
  of 
  greater 
  intensity 
  during 
  the 
  autumn 
  than 
  during 
  the 
  corresponding 
  

   spring 
  months. 
  

  

  There 
  is 
  a 
  remarkable 
  uniformity 
  in 
  this 
  law, 
  the 
  only 
  cases 
  where 
  it 
  

   is 
  broken 
  being 
  the 
  years 
  1855, 
  1857, 
  and 
  1868 
  — 
  years, 
  it 
  may 
  be 
  remarked, 
  

   which 
  are 
  near 
  the 
  epochs 
  of 
  minimum 
  sun-spot 
  frequency. 
  It 
  thus 
  

   appears 
  that 
  in 
  order 
  to 
  compare 
  one 
  set 
  of 
  observations 
  with 
  another, 
  it 
  

   will 
  be 
  necessary 
  to 
  form 
  yearly 
  instead 
  of 
  half-yearly 
  values 
  ; 
  this 
  is 
  done 
  

   in 
  the 
  following 
  Table 
  : 
  — 
  

  

  * 
  Phil. 
  Trans. 
  1867, 
  p. 
  562. 
  

  

  