﻿SOLAR 
  PHYSICS 
  AND 
  LOCUST 
  mCREASE. 
  73 
  

  

  again 
  absent 
  between 
  1686 
  and 
  16S8; 
  other 
  observers 
  found 
  them 
  absent 
  

   between 
  1695 
  and 
  1700. 
  The 
  means 
  of 
  these 
  periods 
  arranged 
  by 
  the 
  

   differences 
  of 
  the 
  series 
  check 
  the 
  seismic 
  numbers 
  correctly, 
  but 
  as 
  re- 
  

   gards 
  the 
  maximum 
  in 
  1681, 
  it 
  becomes 
  evident 
  that 
  the 
  observation 
  of 
  

   Flamsteed 
  is 
  indefinitely 
  given, 
  as 
  it 
  makes 
  a 
  greater 
  interval 
  occur 
  

   between 
  the 
  minimum 
  and 
  maximum 
  of 
  the 
  cycle 
  than 
  between 
  the 
  

   maximum 
  and 
  minimum. 
  In 
  M. 
  Poey's 
  table, 
  before 
  alluded 
  to, 
  the 
  fol- 
  

   lowing 
  years 
  are 
  further 
  given 
  from 
  the 
  strength, 
  number, 
  and 
  extent 
  

   of 
  the 
  earthqnake 
  sliocks 
  in 
  the 
  Brazils, 
  namely 
  : 
  1727 
  M, 
  1712 
  m, 
  1693 
  M, 
  

   and 
  1634 
  M. 
  These 
  in 
  my 
  table 
  stand 
  as 
  1730 
  m, 
  1714 
  M, 
  1691 
  M, 
  and 
  

   1635 
  m, 
  the 
  modification 
  being 
  due 
  to 
  the 
  co-ordination 
  of 
  other 
  seismic 
  

   data 
  and 
  the 
  consecutive 
  marking 
  of 
  the 
  solar 
  phases, 
  only 
  then 
  ren- 
  

   dered 
  possible. 
  Again, 
  it 
  will 
  be 
  noticed 
  that 
  the 
  cycles 
  of 
  sun-spots 
  in 
  

   my 
  table 
  grow 
  short 
  about 
  the 
  beginning 
  of 
  the 
  seventeenth 
  century 
  

   and 
  lengthen 
  out 
  at 
  the 
  commencement 
  of 
  the 
  nineteenth. 
  This 
  circum- 
  

   stance 
  is 
  owing, 
  as 
  I 
  conclude, 
  to 
  the 
  presence 
  of 
  a 
  greater 
  sun-spot 
  cycle 
  

   stretching 
  from 
  1580 
  to 
  1814 
  and 
  marked 
  by 
  the 
  progressive 
  east 
  and 
  

   west 
  deviation 
  of 
  the 
  compass 
  needle. 
  The 
  years 
  1580 
  and 
  1814 
  on 
  this 
  

   greater 
  cycle 
  I 
  would 
  consider 
  to 
  correspond 
  with 
  the 
  maxima 
  of 
  the 
  

   smaller 
  cycles, 
  and 
  some 
  intermediate 
  epoch 
  about 
  1640 
  to 
  correspond 
  

   with 
  the 
  minimum. 
  This 
  would 
  also 
  answer 
  well 
  to 
  the 
  periods 
  of 
  prev- 
  

   alence 
  and 
  scarcity 
  of 
  auroras 
  in 
  Europe. 
  Thus 
  between 
  1574, 
  about, 
  

   and 
  1635, 
  many 
  auroras 
  were 
  observed 
  j 
  few 
  were 
  observed 
  between 
  1635 
  

   and 
  1706; 
  and 
  many 
  were 
  again 
  observed 
  between 
  1706 
  and 
  1842. 
  We 
  

   are 
  now 
  in 
  Europe 
  back 
  again 
  in 
  the 
  period 
  of 
  few 
  auroras, 
  and 
  I 
  con- 
  

   clude 
  at 
  a 
  minimum 
  point 
  in 
  the 
  greater 
  sun-spot 
  cycles, 
  when, 
  judging 
  

   from 
  the 
  past, 
  great 
  extremes 
  of 
  summer 
  and 
  winter 
  temperature 
  may 
  be 
  

   anticipated. 
  

  

  Having 
  drawn 
  up 
  my 
  table, 
  now 
  comes 
  the 
  second 
  clause 
  of 
  the 
  in- 
  

   quiry, 
  namely, 
  how 
  and 
  in 
  what 
  measure 
  the 
  sun 
  phases 
  influence 
  the 
  

   world 
  of 
  insects 
  on 
  the 
  surface 
  of 
  the 
  old 
  and 
  new 
  continents. 
  Before 
  

   setting 
  out 
  on 
  this 
  subject, 
  however, 
  I 
  think 
  it 
  may 
  be 
  inferred 
  that 
  

   where 
  the 
  terrestrial 
  phenomena 
  follow 
  most 
  directly 
  on 
  the 
  changeful 
  

   glare 
  of 
  the 
  solar 
  photosphere, 
  there 
  shall 
  we 
  find 
  the 
  various 
  features 
  

   of 
  insect 
  biology 
  marshaled 
  in 
  the 
  strictest 
  order. 
  As 
  before 
  noticed, 
  

   this 
  phenomenon 
  is 
  to 
  be 
  looked 
  for 
  rather 
  towards 
  the 
  equator 
  than 
  

   in 
  the 
  direction 
  of 
  the 
  i)oles 
  of 
  the 
  diurnal 
  sphere, 
  and 
  here 
  it 
  is 
  that 
  

   insects 
  should 
  be 
  found 
  to 
  multipl}^ 
  and 
  migrate 
  in 
  most 
  immediate 
  de- 
  

   pendence 
  on 
  the 
  sun 
  changes. 
  Let 
  us 
  take 
  that 
  example 
  which 
  most 
  con- 
  

   cerns 
  us, 
  the 
  Rocky 
  Mountain 
  locust 
  (Galopte7ius 
  spretus). 
  The 
  Perma- 
  

   nent 
  Kegion, 
  and 
  native 
  breeding-ground 
  of 
  this 
  insect, 
  as 
  already 
  ably 
  

   shown 
  by 
  the 
  entomologists 
  on 
  the 
  Commission, 
  lies 
  within 
  the 
  northern 
  

   temperate 
  zone, 
  between 
  37° 
  and 
  53*^ 
  north 
  latitude. 
  Though 
  some- 
  

   what 
  removed 
  from 
  the 
  tropics, 
  the 
  summer 
  isotherms 
  would 
  adjudge 
  it 
  

   to 
  be 
  considered 
  within 
  tropical 
  influence, 
  and 
  this 
  even 
  more 
  so 
  than 
  

   Southern 
  Europe, 
  which 
  must 
  be 
  virtually 
  so 
  considered. 
  The 
  migra- 
  

  

  