The vaults belong to three periods. In the first, which belongs to the XVIIIth Dynasty, the tombs are separate vaults hewn here and there in the rock; in the second, which is that of Dynasties XXII to XXV, a long gallery was excavated, on either side of which mortuary chambers were excavated as needed; in the third (XXVIth Dynasty) the gallery plan is followed, but on a much larger scale. The total length of the galleries of the XXVIth Dynasty is 1150 feet, and the great gallery alone measures 640 feet in length. In the side chambers are the immense granite coffins, of superb workmanship, which were provided for the last resting-place of the Apis. Twenty-four of these were found in the third gallery. They average 13 feet in length, 11 feet in height, and 7 feet 8 inches in breadth, and weigh not less than 65 tons apiece, magnificent specimens of the engineering skill of the ancient workers who transported these vast blocks from Aswan to Memphis, a distance of almost 600 miles. The discovery of the Serapeum set the seal on Mariette’s destiny. Henceforward his life-work was to lie in the excavation and preservation of the relics of that ancient land to which fate had brought him; but as yet he occupied no official position in the country, and was, indeed, looked upon rather as an unauthorised interloper by the native antiquity-hunters and the foreign officials who encouraged the constant and shameless pillage which had been going on for half a century. It was in his struggles with these vampires that the great explorer acquired the habits of secret and solitary planning and working which characterised his reign as chief of the Egyptian Service of Antiquities, and the distrust of all other excavators which led him to forbid all such work even to the most famous scholars or to his dearest friends, and to retain the right to excavate exclusively in his own hands to the day of his death.