Pope Julius II. died in 1513, and was succeeded by Leo X., the son of Lorenzo the Magnificent. As a Florentine and his father's son, we might naturally have expected that he would have gloried in patronizing and employing Michael Angelo; but such was not the case. There was something in the stern, unbending character, and retired and abstemious habits of Michael Angelo, repulsive to the temper of Leo, who preferred the graceful and amiable Raphael, then in the prime of his life and genius; hence arose the memorable rivalry between Michael Angelo and Raphael, which on the part of the latter was merely generous emulation, while it must be confessed that something like scorn mingled with the feelings of Michael Angelo. The pontificate of Leo X., an interval of ten years, was the least productive period of his life. In the year 1519, when the Signoria of Florence was negotiating with Ravenna for the restoration of the remains of Dante, he petitioned the pope that he might be allowed to execute, at his own labor and expense, a monument to the "Divine Poet." He was sent to Florence to superintend the building of the church of San Lorenzo and the completion of Santa Croce; but he differed with the pope on the choice of the marble, quarrelled with the officials, and scarcely anything was accomplished. Clement VII., another Medici, was elected pope in 1523. He had conceived the idea of consecrating a chapel in the church of San Lorenzo, to receive the tombs of his ancestors and relations, and which should be adorned with all the splendor of art. Michael Angelo planned and built the chapel, and for its interior decoration designed and executed six of his greatest works in sculpture. While Michael Angelo was engaged in these works his progress was interrupted by events which threw all Italy into commotion. Rome was taken and sacked by the Constable de Bourbon in 1527. The Medici were once more expelled from Florence; and Michael Angelo, in the midst of these strange vicissitudes, was employed by the republic to fortify his native city against his former patrons. Great as an engineer, as in every other department of art and science, he defended Florence for nine months. At length the city was given up by treachery, and, fearing the vengeance of the conquerors, Michael Angelo fled and concealed himself; but Clement VII. was too sensible of his merit to allow him to remain long in disgrace and exile. He was pardoned, and continued ever afterward in high favor with the pope, who employed him on the sculptures in the chapel of San Lorenzo during the remainder of his pontificate. In the year 1531 he had completed the statues of "Night and Morning," and Clement, who heard of his incessant labors, sent him a brief commanding him, _on pain of excommunication_, to take care of his health, and not to accept of any other work but that which his Holiness had assigned him.