Bosio seems to have paid his first visit to the Catacombs, in company with the learned antiquarian Pompeo Ugonio and some others, on the 10th of December 1593. They penetrated into a catacomb about a mile distant from St. Sebastian’s, and having found their way to a lower level by means of an opening in the floor of one of the chapels, they incautiously proceeded so far, that when they wished to return they could not recognise the path by which they had come. To add to their perplexity and alarm, their lights failed them, for they had remained underground much longer than they had intended, and “I began to fear,” he says, “that I should defile by my vile corpse the sepulchres of the martyrs.” However, this accident did not damp his courage nor divert him from his purpose; he only took precautions against its recurrence, and then devoted himself for the remaining thirty-six years of his life to the thorough prosecution of the work he had begun. He gave himself up with untiring energy to researches in the bowels of the earth on the one hand, and among old books and manuscripts on the other. His industry in both was amazing. As to his literary labours, there are still extant some thousands of folio pages in his own handwriting, showing with what care he had read the Fathers, Greek, Latin, and Oriental; the collections of canons and councils, ecclesiastical histories, lives of the saints, and an immense number of theological treatises, including those of the schoolmen; in fact, every work within his reach in which he thought there was a chance of finding anything in illustration of his subject. He had also transcribed numerous Acts of the Martyrs, especially of those who had suffered in Rome, together with any other ancient records which promised to throw light upon the topography of the Christian cemeteries. And when he had learnt in this way something as to the probable position of a catacomb, then began the anxious, fatiguing, and even dangerous work of his subterranean researches. He would examine with the utmost diligence all the neighbouring fields and vineyards, in order to discover, if possible, some entrance by which he could penetrate; and often, after returning again and again to the same spot, his labour still remained unrewarded. At another time he would hear of some opening having been accidentally made into a catacomb, by the digging of a new cellar or a well; and on hastening to the spot, he would find perhaps that the whole place was so buried in ruins that ingress was impossible. Even when an entrance was once effected, he still had to force a passage, often by the labour of his own hands, through the accumulated rubbish of ages; for we must not suppose that the pioneers in the work of exploring the Catacombs after their rediscovery found the galleries clear and empty as they are seen by ordinary visitors at the present day; on the contrary, some were filled to the very roof with soil that had been washed down