In 1841, M. Delectuze discovered, among the manuscripts of Leonardo da Vinci, an entry carrying a knowledge of the steam-engine, applied to warfare, to at least as far back as the fifteenth century. He has published in the _Artiste_, a notice of the life of Leonardo, to which he adds a fac-simile of a page of one of his manuscripts, containing five pen-and-ink sketches of details of the apparatus of a Steam Gun, with an explanatory note on what he designates the "Architonnere." The entry is as follows:-- Invention of Archimedes. The architonnere is a machine of fine copper, which throws balls with a loud report and great force. It is used in the following manner:--One-third of the instrument contains a large quantity of charcoal fire. When the water is well heated, a screw at the top of the vessel which contains the water must be made quite tight. On closing the screw above, all the water will escape below, will descend into the heated portion of the instrument, and be immediately converted into a vapour so abundant and powerful, that it is wonderful to see its force, and hear the noise it produces. This machine will carry a ball a talent in weight." It is worthy of remark that Leonardo da Vinci, far from claiming the merit of this invention for himself or the men of his time, attributes it to Archimedes. The Steam Gun of our time has been an exhibition-room wonder; and the prediction of the Duke of Wellington that it would fail in warfare, has never been, and is never likely to be, tested. ------------------ ANCIENT OBSERVATORY IN PERSIA. When Sir John Malcolm visited Maraga, he traced distinctly the foundations of the Observatory, constructed in the 13th century, for Naser-ood-Deen, the favourite philosopher of the Tartar prince, Hoolakoo, the grandson of Ghenghiz, who, in this locality relaxed from his warlike toils, and assembled round him men of the first genius of the age, who have commemorated his love of science, and given him more fame as its munificent patron, than he acquired by all his conquests.