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of letters, and a geometer, and before proceeding to consider him as a pbysicist, astronomer, and statistician we shall see how be filled the office of professor. When first appointed to the Athenæum of Brussels, he occupied only a very subordinate position, as professor of elementary mathematics, but he was soon promoted, and his duties much extended. In 1824 we find him teaching at the athenæum the descriptive geometry of Menge, the theory of shades and perspective, the calculation of probabilities of La Croix, higher algebra, and analytical geometry; while he was also giving a public course of lectures, at the museum upon experimental physics, the elements of astronomy, and of differential and integral calculus.

He was very highly esteemed by his pupils. There was something about him at once imposing and amiable, wbile there was a complete absence of anything like pedantry or haughtiness. Although marked with small-pox, his physiognomy was refined and impressive; it was only necessary to fix bis large dark eyes, surmounted with heavy black brows, upon the refractory, to insure at once silence and submission. On account of the inefficiency of his assistants, he was obliged each year to commence arithmetic, algebra, and geometry. He separated his pupils, according to their ability, into two classes, occupying adjoining rooms, and he would pass from one to the other apartment, experiencing no difficulty in preserviug silence in both. He was as simple and natural in his teaching as in everything else. He reduced arithmetic to a few general principles, and, as soon as he had initiated his pupils in the notation of algebra, showed how tbis admirable instrument could be used to resolve all ordinary questions relating to numbers. His talent for drawing was displayed by the geometrical figures he formed with chalk upon the blackboard to illustrate his teachings. At the Atheuæum his courses attracted numerous auditors from all classes of society. He had a special talent for exposition, and knew how to use to advantage the few instruments he had at command. He disliked to make experiments with complicated apparatus, which he said was apt to divert the attention from the results exhibited; he considered that only indispensable articles, such as the scales, an electric machine, a voltaic pile, and a few other simple imstruments need be provided.

For the use of his public courses he published several elementary works. The first, upon astronomy, appeared in Paris in 1826. It bas been reprinted many times in France and Belgium and translated into several languages. It was followed by one upon natural philosophy, which was intended to enable his pupils at the museum to correct the notes hurriedly taken at the time of the lecture and often erroneous. We have said that he disliked complicated apparatus in teaching the elements of physics, and he accordingly prepared a small volume, the object of which was to describe observations and experiments which could be easily made by any one. This was published in 1832, and the author intended to follow it with other works of the same kind upon magne

tism, electricity, light, &c. In 1828 he published a review of the lectures given at the museum upon the calculus of probabilities, as an introduction to his course of physics and astronomy.

The public lectures of Quetelet were such a success that the government considered it advisable to institute other courses of the same kind, and on the third of March, 1827, was installed the Museum of Science and Letters, with a corps of efficient professors in the various branches of science and literature. In the review of the lecture with which, three days later, Quetelet opened his course, we find one of his favorite ideas: “ The more progress physical sciences make, the more they tend to enter the domain of mathematics, which is a kind of centre to which they all converge. We may even judge of the degree of perfection to which a science has arrived by the facility with which it may be submitted to calculation.” The museum continued to exist for eight years. After suffering with all the other educational establishments of the country from the effects of the revolution, it was absorbed into the free university in 1834, and Quetelet ceased his public instruction after twenty years of service. He soon commenced again, however, having been appointed professor of astronomy and geodesy to the military school, by a royal decree, on the 6th of January, 1836. Among his pupils at the Athenæum were the Duke of Saxe Coburg Gotha and the late Prince Consort of England, who always retained a warm affection for bis preceptor.

We have said that Quetelet was only twenty-four years of age when made a member of the Brussels Academy. His first contribution, A memoir upon a general formula for determining the surface of a polygon, formed on a sphere, by the arcs of great or little circles, disposed in any man. ner whatever," was an admirable production. Garnier said of it, that its elegant simplicity and the symmetry of the formula lent interest to a subject which would otherwise have appeared very dry. His second memoir, “A new theory of conic sections considered in the solid," did hiin great honor. His third paper was upon the paths followed by light and elastic bodies. We have now come to a subject which occupied much of his attention, to which he devoted three memoirs presented to the academy, and numerous articles in the Correspondance Mathématique et Physique—that is, caustic curres. In one of those articles he gives the following theorem, which in importance is worthy to be ranked with the discovery of the focale: “The caustic by reflexion, or by refraction for any curve whaterer, illuminated by a radiant point, is the developinent of another curve, which has the property of being the envelope of all the circles, which have their centers upon the reflecting or directing eurre, and of wbich the radii are equal to the distances of the centers from the radiant point in the first case, and proportional to these same distances in the second case; the constant relation being that of the sine of incidence to the sine of refraction." It was easy to extend this theorem to surfaces, considering spheres enveloped instead of circles. The memoirs presented to the academy were, February 3, 1823, "Upon circular conchoids;" November 3, 1825, "Review of a new theory of caustics followed by different applications to the theory of stereographic projections." These researches attracted the attention of Gergonne and other distinguished geometers, and were particularly noticed by the illustrious French mathematician, Chasles, after the Correspondence Mat. and Phys. had given them notoriety. We mention two other papers read before the Academy. One, “A memoir upon some graphical constructions of the planetary orbits," and the other “upon different subjects of geometry of three dimensions," presented October 28, 1826.

In 1823 commenced the efforts to found an observatory in Belgium. The especial aptitudes of Quetelet pointed him out as the best person to complete the enterprise, and, thanks to M. Falk, then minister of the interior, he was commissioned to go to Paris to study the practice of astronomy. His own account of his first visit to the observatory may not be uninteresting: “I arrived at Paris near the close of the year 1823, with the prospect of founding an observatory in Belgium, but at the same time with a thorough conviction of my want of knowledge of practical astronomy. I went immediately to the royal observatory, but on entering this building, distinguished by historical associations, I was more than ever oppressed with a sense of my deficiencies. I had not even a letter of introduction to relieve tbe embarrassment of a first visit. I mounted with sufficient assurance the grand staircase, but when I found myself before the doors of Arago and Bouvard I stood for some time irresolute. I was about to knock at the first, when Bouvard opened his and came out, on his way to the observing-halls. He asked me what I wanted. I at once told him my history, to which the excel. lent man seemed to listen with interest. He then introduced me to the observing-rooms, into the presence of the great astronomical instruments, to me a novel and wonderful sight. With great kindness he explained their purpose and use, and gave me permission to observe whenever I chose to do so. I availed myself of this permission that very evening, and to my surprise was allowed access, freely and alone, to the instruments and records of the observatory. I came day after day, and always with the same confidence accorded ! From time to time the kind Bouvard examined my observations and always with encouraging words. He gradually manifested more and more affection for me, offered to initiate me into the practical calculus of astronomy, and from that time directed all my studies, with a care truly paternal. Not content with these man. ifestations of kindness, he invited me to his house, presented me to his friends, among others to La Place and Poisson, admitted me to his Friday dinners, and I became in some sort a member of his household." Quetelet remained in Paris several months, and had the honor of being presented to the institute by Alexander von Humboldt. He returned to Brussels on the first of March, 1824.

To fit himself still further for the office of director of the new obser

ratory, he was sent to the principal establishinents of the kind in Europe, and on this tour he was accompanied by his wife. He had married on the 20th of September, 1825, the daughter of a French physician, and the niece of the chemist Van Mons. To an intimate acquaintance with the usages of polite society this lady united a ready wit and not inconsiderable literary attainments. She was also an excellent musician. Obliged at an early age to preside in the house of her father, where was congregated the best society of Brussels, she acquired ease and grace of manner, and was well prepared to assist her husband when, in after years, he had arrived at distinction, and exercised a generous hospitality toward the distinguished strangers of every country who visited the observatory. During his journey, Quetelet made the acquaintance of some of the most distinguished men of the age of Herschel, Schumacher, Grauss, Olders, and others, and at Weimar he had the pleasure of assisting in the celebration of the eightieth birthday of Goethe, with whom he remained eight days. The great poet showed him his experiments in optics, and entertained him with his theory of colors. He was also present at the conference of German naturalists, held at Heidelberg on the 18th of September.

While waiting the completion of his plans in regard to the observatory, he, in conjunction with M. Garnier, established the periodical La Correspondance Mathématique et Physique, to which the most eminent men of the age were willing contributors. This publication continued without intermission till 1839, when Quetelet was obliged to resign its sapervision on account of the pressing nature of bis engagements as permanent secretary to the academy, to which office he had been elected in 1834.

The erection of the observatory was decided upon on the 8th of June, 1826. It was constructed according to the plans of Que telet, but was not finished till after many vicissitudes, occasioned principally by the political events of 1830. He had been appointed to the directorship in 1818, but the observatory was not completed until 1832. He then immediately commenced bis labors, of which it would occupy too much space to give even a list. They included meteorology, terrestrial physics, astronomy, the collection of materials for the Annales Annuaires of the observatory, and the other special works in which he has brought together the results of his researches. In the early days of the observatory, all the attention of Quetelet was directed toward meteorology and terrestrial physics. The elements of these two sciences had been almost totally neglected in Belgium, and his first desire was to correct this grave error, a task in which he perfectly succeeded. He has given the results of his persevering observations in his works Upon the climate of Belgium, and Upon the physics of the Globe, and thus the basis of the meteorology of Belgium was established. The meteorological observations were commenced in 1833, and also the observations for the determination of the latitude and longitude of the establishment. At that time Quetelet possessed only very few and very inferior astronomical instruments. In the month of July, 1835, the meridian telescope and the mural circle were put in position, but the equatorial was not inounted until June of the following year. Quetelet was anxious to have the turning-dome for the equatorial ready in time to observe Halley's comet, the return of which was looked for with great interest by all Europe, but in spite of all his efforts, and the good will of the government, he was disappointed, and was obliged to follow the course of this eccentric wanderer with only his telescope.

The determination of the difference of longitude between the observatories of Brussels and Greenwich was later a source of great anxiety as well as interest to him, when, in 1853, a trial was made of the new electrical telegraph for this purpose. Two successful attempts of the kind had been made in America, but the distance between the two places, the intervention of the sea, the great reputation of the director of the observatory of Greenwich, and the responsibility assumed before the world, rendered Quetelet very solicitous as to the result of his co-operation, and his anxiety did not cease until the two sealed packets, containing the observations made simultaneously at Greenwich and Brussels, which were by common consent opened on the same day in both places, proved the result to be entirely satisfactory. A similar attempt was made in 1868 between Brussels and Leyden.

At the time the observatory was erected, clocks and watches throughout the country were regulated only by sun-dials, and as these were often defective and liable to get out of order, it frequently happened that there would be a difference in time of from 20 to 25 minutes between the clocks of different towns, and even between those of the same city. The establishment of railroads necessitated more precision, and on the 22d of February, 1836, a royal decree enacted thata meridian should be traced and an instrument of observation be established in forty-one of the prin. cipal cities of the kingdom. The execution of this work was intrusted to Quetelet.

From 1841 to 1845 the observatory of Brussels was the center of a vast meteorological net-work, which comprised more than eighty stations in Europe and in the north of Asia. Its director published the results of this great enterprise, with a large number of plates, showing the course and rapidity of the movements of the atmospheric waves. He also made many observations upon the temperature of the earth, and an un. interrupted series of observations of the elements of terrestrial magnetism. But, perhaps, the most remarkable works of Quetelet were the papers he published on his observations of the periodical phenomena of plants and animals. These gave an impulse to similar studies throughout the whole of Europe, and he may on this account be considered as the founder of a new science.

As a class for the study of the fine arts had been added to the academy, and other changes made, it was deemed advisable to form a

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