Another and a more important change than any which has yet been mentioned came over the Catacombs during the fourth century. It has been already mentioned that the devotion of the faithful naturally led them to look on the tombs of the martyrs with feelings of the most tender and pious affection; they desired, therefore, to manifest their love by some outward tokens—to exchange the primitive simplicity of their humble graves for something more suitable to their own altered condition. From the first moment, then, that it was possible, even in the very age of Constantine, grand basilicas were built over the tombs of the more celebrated saints, St. Peter, St. Paul, St. Agnes, St. Sebastian, and others. In all these instances, they aimed at enclosing the tomb they desired to honour within the precincts of the church; indeed, this was, of course, the central point of devotion in the new building. But it was impossible to dig the foundations and build the walls of such vast edifices without a great destruction of subterranean graves and galleries throughout the whole neighbourhood. Probably there were always some who regretted this necessity, and who would have preferred to see these venerable monuments of primitive Christianity left in their original form. Certainly at the end of some fifty or sixty years, about the year 370, there sat in the chair of Peter one who seems to have entertained these feelings, and who devoted himself therefore with singular zeal and prudence to the work of their preservation.