﻿72 
  REPORT 
  UNITED 
  STATES 
  ENTOMOLOGICAL 
  COMMISSION. 
  

  

  ^^(1839-1838) 
  (1826-1823) 
  

  

  13(1838-1834) 
  (1831) 
  (1830-1829) 
  (182(3-1817) 
  

  

  ^2(1839-1837) 
  (1835-1832) 
  (1830-1828) 
  (1825-1822) 
  

  

  "(1839-1835) 
  (1833-1831 
  ) 
  (1829-1827) 
  (1825-1822) 
  

  

  ^•^(1839-1835) 
  (1833-1831) 
  (1830-1827) 
  (1825-1819) 
  

  

  Let 
  us 
  now 
  mark 
  the 
  epochs 
  of 
  the 
  sun-spot 
  cycle 
  m 
  minimum 
  or 
  M 
  

   maximum, 
  as 
  known 
  from 
  Wolf's 
  tables, 
  to 
  the 
  breaks 
  to 
  which 
  they 
  

   appertain, 
  and 
  at 
  the 
  same 
  time 
  find 
  the 
  mean 
  periods 
  of 
  commotion, 
  

   thus: 
  (1839-1836) 
  M^ 
  (1833-1831) 
  m^ 
  (1830-1828) 
  M^ 
  (1825-1820) 
  m^j 
  

  

  where 
  taking 
  extremes 
  and 
  means 
  Mi 
  = 
  ||??, 
  m^ 
  =^^^, 
  M.^ 
  =^%^^ 
  ^ 
  

  

  m^= 
  1-, 
  the 
  actual 
  years 
  here 
  indicated 
  being 
  given 
  by 
  Wolf 
  as 
  1837, 
  

  

  1822 
  

  

  1833, 
  1829, 
  1823. 
  Here 
  the 
  position 
  of 
  the 
  years 
  is 
  evidently 
  correctly 
  

   found, 
  the 
  maximum 
  in 
  each 
  case 
  being 
  the 
  mean 
  year 
  of 
  commotion 
  

   and 
  the 
  minimum 
  the 
  latter 
  extreme, 
  but, 
  as 
  seen 
  by 
  the 
  last 
  fraction, 
  an 
  

   irregularity 
  does 
  sometimes 
  occur. 
  In 
  calculating 
  out 
  the 
  table, 
  how- 
  

   ever, 
  the 
  latter 
  inconvenience 
  is 
  almost 
  7iiZ, 
  as 
  it 
  will 
  be 
  noticed 
  that 
  the 
  

   known 
  maxima 
  and 
  minima 
  in 
  Wolf's 
  table 
  have 
  certain 
  corresponding 
  

   intervals 
  of 
  years 
  6-4, 
  4-6, 
  6-7, 
  &c. 
  j 
  and 
  also 
  a 
  certain 
  final 
  digit 
  as 
  far 
  

   as 
  they 
  go, 
  the 
  maxima 
  ending 
  in 
  a 
  7, 
  9, 
  6, 
  &c., 
  and 
  the 
  minima 
  in 
  3, 
  3, 
  

   3, 
  0, 
  &c. 
  

  

  Having 
  thus 
  correctly 
  taken 
  out 
  the 
  sun-spot 
  numbers 
  in 
  cycles 
  from 
  

   the 
  seismic 
  breaks 
  between 
  the 
  years 
  1881 
  and 
  1750, 
  we 
  may 
  now 
  pro- 
  

   ceed 
  with 
  confidence 
  to 
  tread 
  on 
  the 
  confines 
  of 
  the 
  unknown, 
  and 
  com- 
  

   plete 
  the 
  series 
  of 
  maximum 
  and 
  minimum 
  years 
  back 
  to 
  1500. 
  Beyond 
  

   this 
  point, 
  the 
  grand 
  epoch 
  when 
  Columbus 
  opened 
  up 
  for 
  eastern 
  civi- 
  

   lization 
  a 
  new 
  continent, 
  and 
  when 
  printing 
  was 
  commenced, 
  the 
  data 
  

   in 
  the 
  seismic 
  tables 
  become 
  involved 
  and 
  partial, 
  and 
  here, 
  at 
  the 
  most, 
  

   I 
  have 
  up 
  to 
  the 
  present 
  only 
  been 
  able 
  to 
  obtain 
  a 
  certain 
  number 
  of 
  

   probable 
  epochs 
  of 
  the 
  solar 
  phases. 
  Sufficient 
  data, 
  however, 
  will 
  be 
  

   found 
  to 
  be 
  present 
  in 
  my 
  table 
  on 
  which 
  to 
  string 
  the 
  more 
  certain 
  

   records 
  of 
  locust 
  multiplication 
  and 
  migration, 
  as 
  known 
  to 
  myself 
  from 
  

   the 
  exhaustive 
  paper 
  b}^ 
  Mr. 
  Thomas 
  in 
  a 
  former 
  issue 
  of 
  your 
  valuable 
  

   report, 
  relating 
  fully 
  the 
  Old 
  World 
  locust 
  multiplication 
  during 
  the 
  

   seventeenth 
  and 
  eighteenth 
  centuries, 
  and 
  from 
  my 
  own 
  investigations 
  

   regarding 
  their 
  increase 
  during 
  the 
  nineteenth 
  j^as 
  also 
  from 
  those 
  clear 
  

   indications 
  alfbrded 
  in 
  Mr. 
  Packard's 
  concise 
  list 
  of 
  the 
  C. 
  spretus 
  years 
  

   in 
  America. 
  But 
  before 
  entering 
  on 
  this 
  subject 
  I 
  ought 
  to 
  mention 
  

   that 
  some 
  of 
  the 
  breaks 
  in 
  my 
  table 
  are 
  substantiated 
  by 
  eye 
  observa- 
  

   tion. 
  Thus 
  Flamsteed 
  tells 
  us 
  that 
  the 
  solar 
  spots 
  were 
  absent 
  between 
  

   the 
  years 
  1676 
  and 
  1684, 
  and 
  according 
  to 
  Dominique 
  Cassini 
  they 
  were 
  

  

  iTrom 
  Eruptions 
  in 
  Iceland, 
  by 
  Thoroddson 
  {Trans. 
  Geol. 
  Mag.). 
  

  

  ^Trom 
  Mods. 
  Perrey's 
  Eartliqnakes 
  in 
  Greece 
  and 
  Syria. 
  

  

  i^From 
  Mons. 
  Poey's 
  Earthquakes 
  in 
  South 
  America. 
  

  

  isprom 
  Mr. 
  Mallet's 
  List 
  of 
  Earthquakes 
  and 
  Volcanic 
  Eruptions 
  (Brit. 
  Assoc), 
  

  

  J'^Erom 
  -works 
  of 
  Lyell 
  and 
  Humboldt. 
  

  

  