LEONARD, an eminent mathematician in the 16th century, was descended from an ancient family, and born at Digges-court in the parish of Barham in Kent; but in what year is not known. He was educated for some time at Oxford, where he laid a good foundation of learning. Retiring from thence, he prosecuted his studies, and became an excellent mathematician, a skilful architect, and an expert surveyor of land, &c. He composed several books: as, 1. Teetonicum: briefly shewing the exact Measuring, and speedy Reckoning of all manner of Lands, Squares, Timber, Stones, Steeples, &c. 1556, 4to. Augmented and published again by his son Thomas Digges, in 1592; and also reprinted in 1647.—2. A Geometrical Practical Treatise, named Pantometria, in three books. This he left in manuscript; but after his death, his son supplied such parts of it as were obscure and imperfect, and published it in 1591, folio; subjoining, "A Discourse Geometrical of the five regular and Platonic bodies, containing sundry theoretical and practical propositions, arising by mutual conference of these solids, Inscription, Circumscription, and Transformation."—3. Prognostication Everlasting of right good effect: or Choice Rules to judge the weather, by the Sun, Moon, and Stars, &c. in 4to, 1555, 1556, and 1564: corrected and augmented by his son, with divers general tables, and many compendious rules, in 4to, 1592. He died about the year 1574.

Thomas, only son of Leonard Digges, after a liberal education from his tenderest years, went and studied for some time at Oxford; and by the improvements he made there, and the subsequent instructions of his learned father, became one of the best mathematicians of his age. When Queen Elizabeth sent some forces to afflit the oppressed inhabitants of the Netherlands, Mr Digges was appointed muster-master general of them: by which he became well skilled in military affairs; as his writings afterwards shewed. He died in 1595.

Mr Digges, besides revising, correcting, and enlarging some pieces of his father's already mentioned, wrote and published the following learned works himself: viz. 1. Alae five Scale Mathematicae; or Mathematical Wings or Ladders, 1573, 4to: A book which contains several demonstrations for finding the parallaxes of any comet, or other celestial body, with a correction of the errors in the use of the radius astronomicus.—2. An Arithmetical Military Treatise, containing so much of Arithmetic as is necessary towards military discipline, 1579, 4to.—3. A Geometrical Treatise, named Stratiotics, requisite for the perfection of Soldiers, 1579, 4to. This was begun by his father, but finished by himself. They were both reprinted together in 1590, with several additions and amendments, under this title: "An Arithmetical Warlike Treatise, named Stratiotics, copiously teaching the science of Numbers, as well in Fractions as Integers, and so much of the Rules and Equations Algebraical, and art of Numbers Cossical, as are requisite for the profession of a folder. Together with the Moderne militaire discipline, offices, laws, and orders in every well-governed camp and armie, inviolably to be observed." At the end of this work there are two pieces; the first, "A briefe and true report of the proceedings of the earle of Leycester, for the relief of the town of Sluce, from his arrival at Vlissing, about the end of June 1587, untill the surrender thereof 26 Juli next ensuing. Whereby it shall plainly appear, his excellencie was not in any fault for the losse of that towne;" the second, "A briefe discourse what orders were best for repelling of foraine forces, if at any time they should invade us by sea in Kent or elsewhere."—4. A perfect Description of the Celestial Orbs, according to the most ancient doctrine of the Pythagoreans, &c. This was placed at the end of his father's "Prognostication Everlasting," &c. printed in 1592, 4to.—5. A humble motive for association to maintain the religion established, 1601, 8vo. To which is added, his Letter to the same purpose to the archbishops and bishops of England.—6. England's Defence: or, A Treatise concerning Invasion. This is a tract of the same nature with that printed at the end of his Stratiotics, and called, A briefe Discourse, &c. It was written in 1599, but not published till 1686.—7. A Letter printed before Dr John Dee's Parallacticæ Commentationis praxeoque nucleus quidam, 1573, 4to.—Besides these, and his Nova Corpora, he left several mathematical treatises ready for the press; which, by reason of lawsuits and other avocations, he was hindered from publishing.