1911 Encyclopædia Britannica/Quetelet, Lambert Adolphe Jacques

QUETELET, LAMBERT ADOLPHE JACQUES (1796-1874), Belgian astronomer, meteorologist and statistician, was born at Ghent on the 22nd of February 1796, and educated at the lyceum of that town. In 1819 he was appointed professor of mathematics at the athenaeum of Brussels; in 1828 he became lecturer at the newly created museum of science and literature, and he continued to hold that post until the museum was absorbed in the free university in 1834. In 1828 he was appointed director of the new royal observatory which it had been decided to found, chiefly at his instigation. The building was finished in 1832, and the instruments were ready for work in 1835, from which date the observations were published in 4to volumes (Annales de l'Observatoire Royal de Bruxelles), but Quetelet chiefly devoted himself to meteorology and statistics. From 1834 he was perpetual secretary of the Brussels Academy, and published a vast number of articles in its Bulletin, as also in his journal, Correspondence mathématique et physique (11 vols., 1825-39). He died at Brussels on the 17th of February 1874. His son, Ernest Quetelet (1825-78), was from 1856 attached to the observatory, and on his death succeeded him as director. He made a great number of observations of stars with proper motion.

Quetelet's astronomical papers refer chiefly to shooting stars and similar phenomena. He organised extensive magnetical and meteorological observations, and in 1839 he started regular observations of the periodical phenomena of vegetation, especially the flowering of plants. The results are given in various memoirs published by the Brussels Academy, and in his works Sur le climat de la Belgique and Sur la physique du globe (the latter forms vol. xiii. of the Annales, 1861). He is, however, chiefly known by the statistical investigations which occupied him from 1823 onward. In 1835 he published his principal work, Sur l'hornme et le développement de ses facultés, ou essai de physique sociale (2nd ed., 1869), containing a résumé of his statistical researches on the development of the physical and intellectual qualities of man, and on the “average man” both physically and intellectually considered. In 1846 he brought out his Lettres à S. A. R. le duc régnant de Saxe-Coburg et Gotha sur la théorie des probabilités appliquée aux sciences morales et politiques (of which Sir J. Herschel wrote a full account in the Edinburgh Review), and in 1848 Du système social et des lois qui le régissent. In these works he shows how the numbers representing the individual qualities of man are grouped round the numbers referring to the “average man” in a manner exactly corresponding to that in which single results of observation are grouped round the mean result, so that the principles of the theory of probabilities may be applied to statistical researches on the subjects. These ideas are further developed in various papers in the Bulletin and in his L'Anthropométrie, ou mesure des différentes facultés de l'homme (1871), in which he lays great stress on the universal applicability of the binomial law,—according to which the number of cases in which, for instance, a certain height occurs among a large number of individuals is represented by an ordinate of a curve the binomial) symmetrically situated with regard to the ordinate representing the mean result (average height). A detailed Essai sur la 'vie et les travaux de L. A. J. Quetelet, by his pupil and assistant E. Mailly, was published at Brussels in 1875.