﻿^4 
  EEPORT 
  UNITED 
  STATES 
  ENTOMOLOGICAL 
  COMMISSION. 
  

  

  chronism 
  may 
  be 
  argued 
  in 
  favor 
  of 
  the 
  occurrence 
  of 
  the 
  plague 
  of 
  

   Barbary, 
  the 
  sweating 
  sickness, 
  and 
  we 
  may 
  say 
  of 
  the 
  black 
  death. 
  

   Yet 
  with 
  none 
  of 
  these 
  disastrous 
  positions 
  on 
  the 
  great 
  cycle 
  does 
  the 
  

   present 
  time 
  agree. 
  If 
  the 
  sun-spot 
  cycles 
  be 
  examined, 
  it 
  will 
  be 
  fur- 
  

   ther 
  seen 
  that 
  we 
  have 
  reached 
  a 
  time 
  when 
  the 
  solar 
  phases 
  are 
  short, 
  

   ^nd 
  that 
  similar 
  short 
  phases 
  are 
  given 
  by 
  the 
  seismic 
  data 
  as 
  having 
  

   transpired 
  about 
  the 
  middle 
  of 
  the 
  seventeenth 
  century, 
  and 
  again, 
  as 
  

   would 
  seem 
  from 
  observed 
  sun- 
  cycles, 
  about 
  the 
  middle 
  of 
  the 
  eighteenth. 
  

   Although 
  the 
  agreement 
  is 
  not 
  exact 
  as 
  regards 
  figures, 
  we 
  still 
  discover 
  

   that 
  the 
  points 
  are 
  marked 
  by 
  the 
  freezing 
  of 
  the 
  Thames, 
  plainly 
  indi- 
  

   cating 
  the 
  passage 
  of 
  intensely 
  cold 
  winters 
  (1670 
  and 
  1683-^4), 
  espe- 
  

   cially 
  in 
  the 
  former 
  case, 
  where 
  there 
  is 
  just 
  previously 
  a 
  change 
  indi- 
  

   cated 
  in 
  the 
  frequency 
  of 
  auroral 
  displays 
  (about 
  1640), 
  that 
  is 
  ahnost 
  

   •synchronous 
  with 
  the 
  great 
  plague 
  of 
  London 
  (1648-1665). 
  Two 
  great 
  

   locust 
  swarms 
  in 
  their 
  sweep 
  over 
  Europe 
  mark 
  the 
  intermediate 
  period 
  

   of 
  time, 
  namely, 
  those 
  of 
  1689 
  and 
  1747, 
  but 
  whether 
  any 
  exact 
  agree- 
  

   ment 
  may 
  exist 
  between 
  the 
  epochs 
  of 
  these 
  visitations 
  of 
  Providence 
  

   I 
  cannot 
  say. 
  They 
  seem 
  to 
  indicate 
  fragments 
  of 
  climatic 
  cycles 
  and 
  

   attendant 
  phenomena, 
  following 
  the 
  greater 
  sun-periods 
  marked 
  by 
  the 
  

   east 
  and 
  west 
  deviation 
  of 
  the 
  compass 
  needle, 
  and 
  corresponding 
  to 
  

   those 
  we 
  have 
  established 
  for 
  the 
  minor. 
  If 
  we 
  may 
  further 
  suppose 
  

   the 
  changes 
  of 
  climate 
  that 
  have 
  transpired 
  between 
  1346 
  and 
  1580 
  to 
  

   have 
  been 
  similar 
  to 
  those 
  that 
  have 
  been 
  experienced 
  since 
  the 
  year 
  

   1814, 
  we 
  might, 
  in 
  picturing 
  to 
  ourselves 
  the 
  multiplication 
  of 
  G. 
  spretus 
  

   during 
  the 
  period 
  1845-1877, 
  call 
  up 
  before 
  the 
  mind's 
  eye 
  the 
  produc- 
  

   tion 
  of 
  that 
  great 
  swarm 
  of 
  grasshoppers 
  that 
  invaded 
  Europe 
  about 
  

   the 
  years 
  1353 
  and 
  1374. 
  Both 
  points 
  of 
  time, 
  to 
  say 
  the 
  least, 
  must 
  have 
  

   been 
  i)retty 
  well 
  identically 
  marked 
  by 
  the 
  point 
  of 
  the 
  compass 
  needle 
  

   on 
  its 
  circuit. 
  

  

  In 
  concluding 
  my 
  essay, 
  in 
  order 
  to 
  assert 
  the 
  noble 
  dignity 
  of 
  my 
  

   subject, 
  in 
  order 
  'to 
  free 
  myself 
  from 
  all 
  calumny 
  from 
  those 
  of 
  my 
  

   brother 
  naturalists 
  untrained 
  to 
  numerical 
  computation, 
  or 
  from 
  impu- 
  

   tation 
  of 
  the 
  black 
  art 
  on 
  the 
  part 
  of 
  those 
  little 
  thinkers 
  who 
  might 
  

  

  '136° 
  W. 
  of 
  Greenwich, 
  or 
  36° 
  E. 
  of 
  Behring's 
  Straits. 
  The 
  ^vealc 
  pole, 
  therefore, 
  lay 
  nearer 
  Europe 
  than 
  

   •mow, 
  and 
  the 
  strong 
  one 
  more 
  remote. 
  Hence 
  the 
  action 
  of 
  the 
  former 
  predominated, 
  and 
  the 
  needle 
  

   'turned 
  westward 
  till 
  1814, 
  in 
  which 
  year 
  it 
  reached 
  its 
  greatest 
  declijiation, 
  and 
  commenced 
  its 
  easterly 
  

   -course." 
  The 
  explanation 
  is 
  equally 
  satisfactory 
  in 
  reference 
  to 
  the 
  southern 
  hemisphere, 
  and 
  the 
  

   •vaiiation 
  at 
  the 
  Cape, 
  where 
  in 
  1G05 
  the 
  weak 
  S. 
  pole 
  was 
  76Jo 
  W. 
  of 
  Greenwich, 
  and 
  the 
  strong 
  S. 
  pole 
  

   : 
  about 
  150° 
  E. 
  of 
  that 
  meridian. 
  The 
  two 
  northern 
  and 
  two 
  southern 
  poles 
  are 
  elsewhere 
  supposed 
  by 
  

   .Sir 
  David 
  Brewster 
  to 
  be 
  the 
  points 
  of 
  greatest 
  cold, 
  while 
  a 
  marked 
  agreement 
  exists 
  between 
  the 
  

   .magnetic 
  (isodynamic) 
  and 
  mean 
  temi)erature 
  (isothermal) 
  lines. 
  

   • 
  James 
  Forbes 
  (Math, 
  and 
  Phys. 
  Science, 
  p. 
  990) 
  says, 
  speaking 
  of 
  the 
  charts 
  of 
  Halley 
  and 
  Hanstecn: 
  

   "It 
  results 
  from 
  these 
  charts 
  that 
  the 
  line 
  of 
  no 
  variation, 
  which 
  in 
  1600 
  formed 
  a 
  remarkable 
  arch- 
  

   like 
  curve, 
  stretching 
  from 
  the 
  Gulf 
  of 
  Mexico 
  to 
  near 
  the 
  North 
  Cape 
  of 
  Norway, 
  then 
  descending 
  

   through 
  Central 
  Europe 
  to 
  the 
  Gulf 
  of 
  Guinea, 
  had, 
  during 
  the 
  seventeenth 
  and 
  eighteenth 
  centuiics, 
  

   become 
  gradually 
  flattened 
  (having 
  passed 
  through 
  Paris 
  in 
  1GC9, 
  and 
  through 
  London 
  twelve 
  years 
  

   earlier), 
  and 
  at 
  present 
  this 
  part 
  of 
  the 
  line 
  of 
  no 
  variation 
  is 
  confined 
  to 
  the 
  American 
  continent 
  and 
  

   neighboring 
  seaa. 
  Another 
  and 
  more 
  complicated 
  branch 
  of 
  the 
  same 
  line 
  traverses 
  the 
  Pacific 
  Oeeau, 
  

   making 
  a 
  coraxilex 
  serpentine 
  track 
  through 
  Eastern 
  Asia 
  and 
  Siberia. 
  The 
  line 
  of 
  no 
  variation 
  may 
  

   •be 
  expected 
  to 
  pass 
  through 
  those 
  points 
  of 
  the 
  earth's 
  surface 
  towards 
  which 
  the 
  needle 
  converges." 
  

  

  