The flooring was loose in the corner, and plank by plank the two savants raised it and leaned it against the wall.  Below there was a square aperture and a stair of old stone steps which led away down into the bowels of the earth.

“Be careful!” cried Burger, as Kennedy, in his impatience, hurried down them.  “It is a perfect rabbits’-warren below, and if you were once to lose your way there the chances would be a hundred to one against your ever coming out again.  Wait until I bring the light.”

“How do you find your own way if it is so complicated?”

“I had some very narrow escapes at first, but I have gradually learned to go about.  There is a certain system to it, but it is one which a lost man, if he were in the dark, could not possibly find out.  Even now I always spin out a ball of string behind me when I am going far into the catacomb.  You can see for yourself that it is difficult, but every one of these passages divides and subdivides a dozen times before you go a hundred yards.”

They had descended some twenty feet from the level of the byre, and they were standing now in a square chamber cut out of the soft tufa.  The lantern cast a flickering light, bright below and dim above, over the cracked brown walls.  In every direction were the black openings of passages which radiated from this common centre.

“I want you to follow me closely, my friend,” said Burger.  “Do not loiter to look at anything upon the way, for the place to which I will take you contains all that you can see, and more.  It will save time for us to go there direct.”

He led the way down one of the corridors, and the Englishman followed closely at his heels.  Every now and then the passage bifurcated, but Burger was evidently following some secret marks of his own, for he neither stopped nor hesitated.  Everywhere along the walls, packed like the berths upon an emigrant ship, lay the Christians of old Rome.  The yellow light flickered over the shrivelled features of the mummies, and gleamed upon rounded skulls and long, white armbones crossed over fleshless chests.  And everywhere as he passed Kennedy looked with wistful eyes upon inscriptions, funeral vessels, pictures, vestments, utensils, all lying as pious hands had placed them so many centuries ago.  It was apparent to him, even in those hurried, passing glances, that this was the earliest and finest of the catacombs, containing such a storehouse of Roman remains as had never before come at one time under the observation of the student.

“What would happen if the light went out?” he asked, as they hurried onwards.

“I have a spare candle and a box of matches in my pocket.  By the way, Kennedy, have you any matches?”

“No; you had better give me some.”

“Oh, that is all right.  There is no chance of our separating.”

“How far are we going?  It seems to me that we have walked at least a quarter of a mile.”