# Catholic Encyclopedia (1913)/Simon Stevin

Born at Bruges in 1548; died at Leyden in 1620. He was for some years book-keeper in a business house at Antwerp; later he secured employment in the administration of the Franc of Bruges. After visiting Prussia, Poland, Sweden, and Norway he took up his residence in the Netherlands, where he spent the rest of his life. The Stadtholder Maurice of Nassau esteemed him so highly that he studied under his direction mathematics, science, and engineering, rewarding him for his services by making him director of finances, inspector of dykes of the Low Countries, and quartermaster-general of the Government. His was an upright, modest, and inventive mind. His influence on the development of science was great and lasting. He began with the publication in 1582 of his "Tafelen van Interest" (Tables of Interest; Plantin, Antwerp), thus distributing through the business world an easy and valuable method of calculation, still carefully preserved by the wealthy merchants of the Low Countries. Then came successively: in 1583 the "Problematum geometricorum libri V", a very original work, somewhat imperfectly reproduced in subsequent editions of the author's works, the "Dialektike ofte bewysconst", a treatise on logic, re-edited at Rotterdam in 1621, but not found in the large editions of the author's works, and "De Thiende", a small pamphlet of thirty-six pages containing the oldest systematic and complete explanation of decimal calculus, both published by Plantin at Leyden in 1585. "De Thiende" has often caused its author to be regarded as the inventor of calculus; he was indisputably the first to bring to light its great advantages. Stevin translated the pamphlet into French and re-edited it the same year under the title "La Disme", with his Arithmetic published at Antwerp by Plantin. In 1586 appeared the most famous of his works, "De Beghinselen der Weeghconst, De Weeghdaet, De Beghinselen der Waterwichts" (Antwerp). This was the first edition of his mechanics, in which he sets forth for the first time several theorems since then definitely embodied in science; the hydrostatic paradox; equilibrium of bodies on inclined planes; the parallelogram of forces, formulated, it is true, under a different enunciation by constructing a triangle by means of two components and their results.

Stevin's "Vita politica, Het Burgherlick leven", a treatise on the duties of the citizen which is no longer printed in large editions of his works, was published by Raphelengen at Leyden in 1590. It gave rise during the nineteenth century to a long and violent controversy. From some pages of this volume the inference has been drawn that when entering the service of Maurice of Nassau Stevin apostatized from the Catholic Church, but this opinion is hardly tenable and has now been abandoned. In 1594 appeared the "Appendice Algebraïque", an eight-page pamphlet, the rarest of his works (there is a copy at the Catholic University of Louvain) and one of the most remarkable; in it he gave for the first time his famous solution for equations of the third degree by means of successive approximations. In the same year was published "De Sterctenbouwing", a treatise on fortifications, and in 1599, "Havenvinding", a treatise on navigation, instructing mariners how to find ports with the aid of the compass. From 1605 to 1608 Stevin re-edited his chief works in two folio volumes entitled "Wisconstige gedachtenissen" (Bouwenz, Leyden). A Latin translation of them, under the title "Hypomnemata mathematica", was confided to Willebrord Snellius; and an incomplete French translation, entitled "Mémoires mathématiques", was the work of Jean Tuning, secretary of the Stadtholder Maurice. These two versions were published at Leyden by Jean Paedts. The "Wisconstige gedachtenissen" and the "Hypomnemata mathematica" contain several treatises then published for the first time, notably the trigonometry, geography, cosmography, perspective, book-keeping, etc.

In 1617 Waesberghe published at Rotterdam Stevin's "Legermeting" and "Nieuwe maniere van Stercktebouw door spilsluysen", of which French translations were published by the same editor in the following year under the titles "Castramétation" and "Nouvelle manière de fortifications par écluses". These were the last publications made during his lifetime, but he left important MSS., the chief of which were published in 1649 by his son Henri, who composed the "Burghelicke Stoffen" (political questions); the others were lost, but later recovered. Bierens de Haan edited two of them at Amsterdam in 1884: "Spiegeling der singconst" (mirror of the art of singing) and "Van de molens" (on mills). After Stevin's death Albert Girard translated several of his works and annotated others, thus forming a large folio volume published at Leyden in 1634 by the Elzevirs as "OEuvres mathématiques de Simon Stevin de Bruges". Abroad Stevin is often known only through this translation, but it does not convey an adequate idea of his works and should be supplemented by several of the original editions mentioned above. Unfortunately these have become bibliographical rarities almost unobtainable outside of Belgium and the Netherlands. M. Ferd. van der Haeghen has made them the subject of a masterly study in his "Bibliotheca Belgica" (1st series, XXIII, Ghent and The Hague, 1880-90), in which he notes most of the copies preserved in the libraries of both countries.

GOETHALS, *Notice hist. sur la vie et les travaux de Simon Stevin de Bruges* (Brussels, 1846); STEICHEN, *Mém. sur la vie et les travaux de Simon Stevin* (Brussels, 1846); CANTOR, *Vorlesungen über Gesch, des Mathematik*, II (2nd ed., Leipzig, 1900).

H. BOSMANS