History OR the catacombs. — Circumstances under which the Christians began the excavations. They were used for burial, for religious assembly, and for conceal ment. S. Jerome's description of the Catacombs. 'la manarza. Ventilation. Changes in the time of Constan tine. Translation, Of the relics of martyrs. The Cata combs not mentioned from the thirteenth to the fifteenth century. Bosic'e discoveries. Labours Of Father Marchi. Appointment Of a commission by Pope Pius IX, to super intend new excavations in the Catacombs. Page 18.