"I have here in my service Francesco di Giorgio, your fellow-citizen and my most favourite architect, who desires to be placed in your magnificent magistracy, as the ambition of his genius, excellence, prudence, and worth. I therefore pray your Highnesses that you will be pleased to elect him thereto, and to admit him into the number of your public men, which I shall regard as a special boon, as will be more fully stated to you on my behalf by your mighty ambassador. And your Lordships may be assured that were I not convinced that only good, faithful, and useful service is to be looked for from him, I should not propose him, nor intercede in his favour. And nothing more gratifying could I ever receive from your Lordships, to whom I offer and commend myself. "From Durante, the 26th July, 1480. "FEDERICUS DUX URBINI AC DURANTIS COMES, et Regius Capit. Gener., et S. Ro. Ecclesie Gonfalonierus."[160] [Footnote 160: MSS. in Public Library at Siena; printed in Bottari, Lettere Pittoriche I. App. No. 36, and in Gualandi, Memorie Artistiche.] Although this request was unsuccessful, so well was Francesco appreciated at home, that on several occasions Duke Guidobaldo vainly applied to the magistracy for his services. Yet he was frequently employed in the duchy from 1484 to 1489, the palace at Gubbio affording him partial employment. His military reputation being now widely spread, he had commissions from various princes, especially the sovereigns of Milan and Naples; but through these labours we need not follow him. The time of his death is not known; he, however, outlived most of the fortresses he had raised for Federigo, which were dismantled by order of his son, on abandoning his state in 1502, a policy suggested by confident reliance on his subjects' attachment, as the best guarantee of his eventual restoration. Francesco's MSS., dispersed in various libraries, are described in Promis's first volume. One of them, on architecture, transcribed for Guidobaldo II., was presented by him to Emanuel Filibert, Duke of Savoy, in 1568, and now ornaments the Royal Library at Turin. The invention of that variety of bastion called in Italy _baluardo_, and in Germany _bollwerk_, has been claimed for several engineers, among whom are three names belonging to Urbino,--Duke Francesco Maria I., Centogatti the painter, and Commandino the mathematician. Promis, in the second volume of his work already quoted, disposes of all these pretensions in favour of Francesco di Giorgio. His learned discussion may be allowed to decide this point, to which little interest now attaches, as well as the question of explosive mines for the destruction of military defences. Such an application of gunpowder had already been partially resorted to, but the Sienese engineer first established its importance and methodised its application. CHAPTER XXVIII