* * * * * Although we have been led to mention engineers in connection with mathematical science, they were in these days usually architects, and regarded as belonging to the class of artists. Ricotti informs us that no vocation was more varied or laborious. Uniting the practice of arms with an intimate knowledge of design, their services were sought for in every part of Europe, either to plan fortresses, build palaces, cast statues, paint frescoes, execute hydraulics, or command troops. Lazzari, in his _Uomini Illustri del Piceno_, enumerates sixteen such as conferring lustre upon Urbino, but of these we shall only name one more. MUZIO ODDI was nobly born there, in 1569. In 1595, he accompanied, as military engineer, a contingent sent by the Duke into Burgundy; and, three years after, employed his architectural skill for the festive decorations in honour of a visit by Clement VIII. to his native city. He had less success in placing a cupola upon the cathedral there, in 1604, which was said to contain 100,000 pounds of iron-work and 80,000 of lead, the weight of which brought it down in 1789. On some indistinctly recorded charge, he was thrown into the citadel of Pesaro, and there detained many years in a loathsome dungeon. Denied the use of books or writing materials, he made for himself ink of charcoal and candle-soot, mixed with water in a walnut-shell, and, by pasting together shreds of paper with bread-dough, contrived to jot down mathematical treatises on sundials and the square, using for compasses a couple of twigs tied together. On his liberation, in 1609, he passed into Lombardy, and spent above twenty years of exile in sighing for his country; nor was it till within two years of the close of life that he was appointed mathematical professor at Urbino. He died at seventy, leaving a Treatise on Mathematics, in two volumes 4to. * * * * *