In describing the works at S. Miniato, Condivi lays great stress upon Michelangelo's plan for arming the bell-tower. "The incessant cannonade of the enemy had broken it in many places, and there was a serious risk that it might come crashing down, to the great injury of the troops within the bastion. He caused a large number of mattresses well stuffed with wool to be brought, and lowered these by night from the summit of the tower down to its foundations, protecting those parts which were exposed to fire. Inasmuch as the cornice projected, the mattresses hung free in the air, at the distance of six cubits from the wall; so that when the missiles of the enemy arrived, they did little or no damage, partly owing to the distance they had travelled, and partly to the resistance offered by this swinging, yielding panoply." An anonymous writer, quoted by Milanesi, gives a fairly intelligible account of the system adopted by Michelangelo. "The outer walls of the bastion were composed of unbaked bricks, the clay of which was mingled with chopped tow. Its thickness he filled in with earth; and," adds this critic, "of all the buildings which remained, this alone survived the siege." It was objected that, in designing these bastions, he multiplied the flanking lines and embrasures beyond what was either necessary or safe. But, observes the anonymous writer, all that his duty as architect demanded was that he should lay down a plan consistent with the nature of the ground, leaving details to practical engineers and military men. "If, then, he committed any errors in these matters, it was not so much his fault as that of the Government, who did not provide him with experienced coadjutors. But how can mere merchants understand the art of war, which needs as much science as any other of the arts, nay more, inasmuch as it is obviously more noble and more perilous?" The confidence now reposed in him is further demonstrated by a license granted on the 22nd of February 1530, empowering him to ascend the cupola of the Duomo on one special occasion with two companions, in order to obtain a general survey of the environs of Florence. Michelangelo, in the midst of these serious duties, could not have had much time to bestow upon his art. Still there is no reason to doubt Vasari's emphatic statement that he went on working secretly at the Medicean monuments. To have done so openly while the city was in conflict to the death with Clement, would have been dangerous; and yet every one who understands the artist's temperament must feel that a man like Buonarroti was likely to seek rest and distraction from painful anxieties in the tranquillising labour of the chisel. It is also certain that, during the last months of the siege, he found leisure to paint a picture of Leda for the Duke of Ferrara, which will be mentioned in its proper place.