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%\ Edited English typescript,E.S. 3 February,1999. Corrections suggested
%by Jongmans have been incorporated. Approved by Droesbeke. Final sighting by ES 20 April 1999. 


\noindent{\bf Adolphe QUETELET} \\
b. 22 February 1796 - d. 17 February 1874
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\noindent 
{\bf Summary}. Active in many area of science, notably mathematics, 
astronomy and meteorology,
Adolphe Quetelet owes his celebrity to the international blossoming 
under his impetus of the
study of populations, emanating from sophisticated statistics 
organized systematically and treated probabilistically.
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   Lambert-Adolphe-Jacques Quetelet, who became known mainly under the first
name of Adolphe, was the fifth in a large family of nine children, not all 
of whom survived to adulthood.  He was born in Ghent, where his father 
Fran\c cois Quetelet, a Frenchman from Picardy, had established himself 10 years 
earlier, and in 1790 had married Anne-Fran\c coise Van de Velde, a Walloon from 
the south of Brabant.  He grew up close to his father, who was involved as a
municipal officer in the political activities of the city of Ghent.
 
   In the course of his studies at the Ghent Lyc\'ee, Adolphe  appears to 
have adapted himself to the upheavals of the educational system without 
serious 
problems.  This was the period of transition from the Austrian educational 
structure current under the Empress Maria Theresia, which prevailed in the 
Austrian Netherlands until 1790, to the French republican organization and its 
immediate imperial successor.  His father's death in 1803, while not 
preventing him from completing his secondary studies brilliantly, placed 
his family in 
financial difficulties.  To cope with these, on leaving the Lycee in 1813, he 
immediately took up teaching duties, and after the fall of Napoleon was 
appointed mathematics teacher at the Ghent municipal college, which had 
replaced the imperial Lyc\'ee. When the University of Ghent was founded in 1817, 
he took the opportunity 
of enrolling in the new institution's Faculty of Sciences.  He was awarded
his Doctorate of Science 2 years later for a thesis in Latin on a geometrical
topic, through which his name became associated with the concept of a focal curve.
 
   In an era marked by great changes in the political structures within 
Europe, 
Quetelet was on the look-out for any avenue which would allow him to progress 
in his career.  In October 1819, he was appointed professor at a scholarly 
institution in Brussels, and elected to the  Academy of this city.  He 
had impressed its members not only by the value of the results in his doctoral 
thesis, but also by his human qualities: this young 
mathematician 
also exhibited a taste for art and poetry, literature and languages.  He also 
felt an immense urge to participate in the development of 
Brussels, the city in which he was to live until the end of his days.
 
   His growing renown was to put him in touch with the then Minister for 
Public Education; this was in 1823, when Brussels had once again become a 
city of the southern Netherlands.  The Minister had lent his support to a project 
which Quetelet championed vigorously:  the creation of a city observatory, to 
develop scientific activities related to astronomy.  Quetelet argued the case 
so convincingly that he was sent to Paris to learn the practice of astronomy, 
and prepare plans for the construction and equipment of the observatory. 
 
   His sojourn in the French capital proved to be most rewarding.  Alexis 
Bouvard, the director of the Paris observatory, benevolently took him under 
his wing.  Quetelet enthusiastically acquired all that he needed to carry out his 
project.  He returned to Brussels with physics instruments 
but even more importantly, and beyond his astronomical mission, his meetings 
with Lacroix, Poisson (q.v.) and Fourier and 
his contacts with Laplace (q.v.) had convinced him of the essential role of probability 
theory.
 
   In Brussels again, he immersed himself in the construction of the
observatory .  For almost 4 years, he travelled to various
countries visiting 
the main observatories of the time, and acquiring instruments.  But during 
this period, he also popularized in Belgium the knowledge he had gained during his stay 
in Paris.  He organized public lectures in experimental physics 
and astronomy at the Brussels Museum, where they proved enormously successful.  
He wrote popular works on science, publishing  {\it Astronomie 
\'el\'ementaire} in 1826, followed by  {\it Astronomie populaire } and {\it Positions de 
physique} in 1827, and {\it Instructions populaires sur le calcul des probabilit\'es} 
in 1828.  In addition, he founded a periodical review {\it Correspondance 
math\'ematique et physique} together with Garnier, his thesis director;  this 
was to enable him to communicate his mathematical papers to a wide audience, 
and so establish close collaboration with numerous foreign colleagues.  He also 
ventured into the field of applied statistics with his paper on the laws of 
births and mortality in Brussels, published in 1826, and   similar research 
led him to demand a complete 
population census, decreed in 1828. Eventually, as President of the Commission
 Centrale
de Statistique of Belgium, he was to take an active part in the census of 1846.  
  
   The year 1828 was a turning point in Quetelet's life:  he was appointed 
astronomer of the Brussels Observatory (which was to be inaugurated only 4 
years later), and decided to redouble his efforts to complete its construction.
He gave up his professorial duties, and travelled to foreign observatories:
he happened to be in Italy when he learned the news of the Belgian Revolution 
in September 1830.  The government of the new state of Belgium rapidly 
confirmed 
him in the post of director of ``his" observatory.  He was to live with his new 
nationality during the next 25 years of splendid achievement, as much in his 
intellectual and scientific activities as in his involvement in the public 
life of his country.
 
   In 1834, he was elected Perpetual Secretary of the Acad\'emie des Sciences et
Belles-Lettres de Bruxelles, which was to become the Royal Academy of Belgium 
in 1845;  he held this position until his death.  Within this august 
institution 
he played an essential role as  indefatigable organizer of its activities 
and publications.  The yearbooks and bulletins of the Academy, in particular, 
were to prove important media for the diffusion of his works, as well as those 
of his colleagues.
 
   In 1836, he had the opportunity of emphasizing once again his interest in 
the calculus of probabilities.  The occasion was his tutoring of princes 
Ernest and Albert of Saxe-Coburg and Gotha, the latter to become the future 
consort of Queen Victoria of Great Britain.  Albert was very impressed by 
Quetelet, and later played an important role in fostering his relations with 
British scientists. The lessons which Quetelet gave  are the basis of an important 
work in his opus, published in 1846 under the title {\it Lettres \`a S.A.R. le Duc 
r\'egnant de Saxe-Cobourg et Gotha, sur la th\'eorie des probabilit\'es appliqu\'ees 
aux sciences morales et politiques.}  The epistolary form of this work 
highlights the pedagogical qualities of the author, but its specific 
importance  lies in Quetelet's developing concern to apply the fundamental rules of
probability theory in the study of human populations. This problem had interested 
Quetelet since 1825 and was to continue into the 1830's.
In 1835, he decided to consolidate his oeuvre by publishing a book  entitled
{\it Sur l'homme et le d\'eveloppement 
de ses facult\'es,} adding the subtitle {\it Essai de physique sociale} which was to 
give rise to many controversies.  Many of the reactions to the book concerned 
Quetelet's concept of {\it l'homme moyen}( the average man), and the 
question  whether Quetelet's theories were deterministic or not.  The literary rather
than technical form of Quetelet's 
expository style was prone to many misunderstandings.
 
   Quetelet's continuing activity in diverse areas of research is illustrated 
by two later works: {\it Du syst\`eme social et des lois 
qui le r\'egissent}, and {\it Sur le climat de la Belgique} published respectively 
in 1848 and 1849.  In Brussels in 1853, he also organized and presided over  the
International Maritime Conference, whose brief was to establish a 
uniform 
system for meteorological observations, as well as over the First International 
Congress of Statistics, which was to be followed periodically by similar 
meetings in other cities.  The principle of such meetings was to be emulated when 
the International Statistical Institute was created.  
 
   His brilliant career was affected by a stroke in 1855. For nearly the 
next 20 years, he 
devoted himself mainly to the republication or issue of supplemented editions 
of his earlier works. He was able to indulge his interest in the history of science;
this took the form of 
publishing, particularly in the yearbooks of the Belgian Academy, various 
biographical notices; and also producing two books on the history of
mathematics and physics in Belgium ( 1864 and 1867).
 He continued to attend the International Congresses of 
Statistics, where he was always an prominent participant. 
 
    The diversity of his foci of interest may help to 
explain the occasionally superficial nature of his works.  He was  an
enthusiast and polymath rather than a deep theoretician.  A visit to England
in the 1830's when he met Babbage and Malthus (q.v.) amongst others, had been
influential in the eventual formation of the Statistical Society of London,
later to become the Royal Statistical Society. His numerous contacts and warm
personality led him on more than one occasion to defend or favour the career of an individual
whose merits he had recognized.  This was particularly the case for the 
mathematicians Dandelin and Pagani, and for his disciple and future biographer 
Mailly. One might  aver 
that Quetelet in the smaller Belgium played a role in the recruitment of scientists similar to 
that of Alexander von Humboldt in Germany.  The family archives have
a letter in which Humboldt recommends a young German scholar to 
Quetelet; this was Theodore Schwann, the founder of cellular theory, who was 
to pursue a brilliant career in Belgium.

 As a result of Quetelet's activities, a gigantic network of sources of his 
correspondence exists, of which 
there is still no complete inventory. It includes correspondence with many of
various scientists of his day, such as the leading French statistician Bienaym\'e (q.v.),
and the mathematician
Catalan who eventually made a career in Belgium. 
Thus it was that Quetelet died on the night  between the 16th to the 
17th of February 1874, having continued his work in the interests
of science till the very end.
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\begin{thebibliography}{3}
\bibitem{1}  Actes du colloque (1997). {\it Actualit\'e et 
universalit\'e de la pens\'ee scientifique d'Adolphe Quetelet}
(24-25 octobre 1996). Acad\'emie Royale de Belgique, Brussels.
(Papers collected under the scientific direction of J.-J.Droesbeke).

\bibitem{2}  Droesbeke, J.-J. and Tassi, P. (1997). {\it Histoire de la
Statistique}. $2^{e}$ \'edition corrig\'ee. Coll. Que sais-je? , {\bf 2527},
Presses Universitaires de France, Paris.

\bibitem{3}  Mailly, E. (1875). Essai sur la vie et les ouvrages de
Quetelet. {\it Annuaire de l'Acad\'emie Royale des Sciences, des
Lettres et des Beaux-Arts de Belgique}, $41^{e}$ ann\'ee, 109-297.

\bibitem{4}  Porter, T.M. (1986). {\it The Rise of Statistical Thinking}. 
Princeton University Press, Princeton NJ.

\bibitem{5}  Stigler, S,M. (1986). {\it The History of Statistics: The
Measurement of Uncertainty Before 1900}. Harvard University
Press, Cambridge MA.
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\hfill{ Jean-Jacques Droesbek and Fran\c cois Jongmans}

  
 
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