﻿xvi 
  

  

  appears, 
  however, 
  to 
  have 
  been 
  in 
  some 
  uncertainty 
  as 
  to 
  the 
  nature 
  of 
  

   these 
  phenomena. 
  

  

  The 
  year 
  1839 
  was 
  marked 
  at 
  the 
  Observatory 
  by 
  the 
  commencement 
  

   of 
  the 
  observations 
  on 
  the 
  flowering 
  of 
  plants, 
  and 
  in 
  the 
  month 
  of 
  January 
  

   was 
  begun 
  the 
  first 
  of 
  a 
  series 
  of 
  monthly 
  magnetic 
  observations. 
  These 
  

   last 
  observations 
  were 
  made 
  at 
  the 
  suggestion 
  of 
  the 
  Eoyal 
  Society 
  of 
  

   London. 
  It 
  was 
  in 
  the 
  year 
  1839 
  that 
  Quetelet 
  was 
  elected 
  a 
  Foreign 
  

   Member 
  of 
  the 
  Eoyal 
  Society; 
  and 
  in 
  May 
  1841 
  these 
  observations 
  were 
  

   considerably 
  extended, 
  and 
  were 
  thenceforth 
  made 
  regularly 
  day 
  and 
  night 
  

   at 
  intervals 
  of 
  two 
  hours. 
  

  

  The 
  year 
  1841 
  was 
  an 
  important 
  period 
  of 
  Quetelet's 
  life. 
  He 
  

   thought 
  that 
  the 
  time 
  was 
  past 
  for 
  individuals 
  to 
  promote 
  the 
  advance- 
  

   ment 
  of 
  science 
  by 
  their 
  isolated 
  efforts, 
  and 
  that 
  further 
  investigations 
  

   would 
  need 
  to 
  be 
  conducted 
  by 
  people 
  associated 
  together 
  in 
  academic 
  

   bodies. 
  In 
  1842 
  he 
  drew 
  up 
  a 
  set 
  of 
  instructions 
  as 
  to 
  the 
  choice 
  of 
  

   subjects 
  for 
  the 
  reports. 
  These 
  instructions 
  embraced 
  Meteorology 
  and 
  

   Physical 
  Geography 
  and 
  the 
  Animal 
  Kingdom. 
  

  

  In 
  1846 
  Quetelet 
  published 
  " 
  Lettres 
  a 
  S.A.E. 
  le 
  due 
  regnant 
  de 
  Saxe 
  

   Coburg 
  sur 
  la 
  theorie 
  des 
  probabilites 
  appliques 
  aux 
  Sciences 
  Morales 
  et 
  

   Politiques," 
  which 
  was 
  reviewed 
  by 
  Sir 
  John 
  Herschel 
  in 
  the 
  ' 
  Edinburgh 
  

   Eeview.' 
  Soon 
  afterwards 
  he 
  published 
  a 
  work 
  entitled 
  " 
  Du 
  Systeine 
  

   Sociale 
  et 
  des 
  lois 
  qui 
  le 
  regissent." 
  

  

  The 
  Eevolution 
  of 
  1848 
  turned 
  Quetelet's 
  thoughts 
  to 
  political 
  ques- 
  

   tions 
  ; 
  and 
  in 
  1849 
  he 
  read 
  to 
  the 
  Academy 
  a 
  new 
  note, 
  entitled 
  " 
  Frag- 
  

   ments 
  sur 
  la 
  maniere 
  dont 
  il 
  convient 
  d'envisager 
  les 
  Sciences 
  Politiques 
  et 
  

   sur 
  l'intervention 
  du 
  gouvernement 
  dans 
  les 
  affaires 
  des 
  particuliers." 
  He 
  

   also 
  presented 
  to 
  the 
  literary 
  section 
  of 
  the 
  Academy 
  a 
  1 
  Note 
  sur 
  la 
  Nature 
  

   des 
  Etats 
  constitutionels, 
  et 
  sur 
  quelques 
  principes 
  qui 
  en 
  derivent.' 
  

  

  Quetelet 
  had 
  in 
  1841 
  organized 
  a 
  general 
  system 
  of 
  observation 
  of 
  

   the 
  periodical 
  phenomena 
  of 
  vegetation. 
  Eive 
  years 
  later 
  he 
  attempted 
  

   to 
  solve 
  the 
  question 
  as 
  to 
  the 
  influence 
  of 
  temperatures 
  on 
  these 
  phe- 
  

   nomena 
  ; 
  and 
  he 
  was 
  led 
  to 
  appreciate 
  the 
  influence 
  of 
  heat, 
  not 
  according 
  

   to 
  the 
  sum 
  of 
  the 
  mean 
  daily 
  temperatures, 
  as 
  did 
  Eeaumur, 
  but 
  by 
  the 
  

   sum 
  of 
  their 
  squares. 
  

  

  The 
  results 
  of 
  these 
  researches 
  on 
  the 
  electricity 
  of 
  the 
  atmosphere 
  

   appeared 
  in 
  1849. 
  Two 
  years 
  afterwards 
  Quetelet 
  made 
  an 
  important 
  

   investigation 
  on 
  the 
  shape, 
  size, 
  and 
  velocity 
  of 
  atmospheric 
  waves, 
  

   according 
  to 
  the 
  observations 
  made 
  in 
  June, 
  July, 
  and 
  August 
  1841, 
  and 
  

   of 
  the 
  system 
  of 
  atmospheric 
  waves 
  of 
  Central 
  Europe, 
  according 
  to 
  

   hourly 
  observations 
  of 
  the 
  summer 
  solstice 
  of 
  1841 
  and 
  of 
  the 
  winter 
  

   solstice 
  of 
  1843. 
  

  

  This 
  work 
  on 
  atmospheric 
  waves 
  was 
  an 
  important 
  step 
  in 
  meteo- 
  

   rology, 
  and 
  paved 
  the 
  way 
  for 
  the 
  recent 
  labours 
  in 
  international 
  meteo- 
  

   rology, 
  to 
  which 
  we 
  owe 
  the 
  remarkable 
  law 
  of 
  tempests 
  of 
  M. 
  Marie- 
  

   Davy. 
  The 
  researches 
  on 
  the 
  temperature 
  of 
  the 
  earth, 
  of 
  which 
  the 
  

  

  