“More than that, I think.  There is really no limit to the tombs—­at least, I have never been able to find any.  This is a very difficult place, so I think that I will use our ball of string.”

He fastened one end of it to a projecting stone and he carried the coil in the breast of his coat, paying it out as he advanced.  Kennedy saw that it was no unnecessary precaution, for the passages had become more complex and tortuous than ever, with a perfect network of intersecting corridors.  But these all ended in one large circular hall with a square pedestal of tufa topped with a slab of marble at one end of it.

“By Jove!” cried Kennedy in an ecstasy, as Burger swung his lantern over the marble.  “It is a Christian altar—­probably the first one in existence.  Here is the little consecration cross cut upon the corner of it.  No doubt this circular space was used as a church.”

“Precisely,” said Burger.  “If I had more time I should like to show you all the bodies which are buried in these niches upon the walls, for they are the early popes and bishops of the Church, with their mitres, their croziers, and full canonicals.  Go over to that one and look at it!”

Kennedy went across, and stared at the ghastly head which lay loosely on the shredded and mouldering mitre.

“This is most interesting,” said he, and his voice seemed to boom against the concave vault.  “As far as my experience goes, it is unique.  Bring the lantern over, Burger, for I want to see them all.”

But the German had strolled away, and was standing in the middle of a yellow circle of light at the other side of the hall.

“Do you know how many wrong turnings there are between this and the stairs?” he asked.  “There are over two thousand.  No doubt it was one of the means of protection which the Christians adopted.  The odds are two thousand to one against a man getting out, even if he had a light; but if he were in the dark it would, of course, be far more difficult.”

“So I should think.”

“And the darkness is something dreadful.  I tried it once for an experiment.  Let us try it again!” He stooped to the lantern, and in an instant it was as if an invisible hand was squeezed tightly over each of Kennedy’s eyes.  Never had he known what such darkness was.  It seemed to press upon him and to smother him.  It was a solid obstacle against which the body shrank from advancing.  He put his hands out to push it back from him.

“That will do, Burger,” said he, “let’s have the light again.”

But his companion began to laugh, and in that circular room the sound seemed to come from every side at once.

“You seem uneasy, friend Kennedy,” said he.

“Go on, man, light the candle!” said Kennedy impatiently.

“It’s very strange, Kennedy, but I could not in the least tell by the sound in which direction you stand.  Could you tell where I am?”