“Looks rather like a wharf where good-sized vessels have been moored, does it not, Uncle Horace?” said Leo, with an excited grin.

I tried to say “Nonsense” again, but the word stuck in my throat—­the ring spoke for itself.  In some past age vessels had been moored there, and this stone wall was undoubtedly the remnant of a solidly constructed wharf.  Probably the city to which it had belonged lay buried beneath the swamp behind it.

“Begins to look as though there were something in the story after all, Uncle Horace,” said the exultant Leo; and reflecting on the mysterious negro’s head and the equally mysterious stonework, I made no direct reply.

“A country like Africa,” I said, “is sure to be full of the relics of long dead and forgotten civilisations.  Nobody knows the age of the Egyptian civilisation, and very likely it had offshoots.  Then there were the Babylonians and the Phoenicians, and the Persians, and all manner of people, all more or less civilised, to say nothing of the Jews whom everybody ‘wants’ nowadays.  It is possible that they, or any one of them, may have had colonies or trading stations about here.  Remember those buried Persian cities that the consul showed us at Kilwa."[*]

[*] Near Kilwa, on the East Coast of Africa, about 400 miles south of Zanzibar, is a cliff which has been recently washed by the waves.  On the top of this cliff are Persian tombs known to be at least seven centuries old by the dates still legible upon them.  Beneath these tombs is a layer of debris representing a city.  Farther down the cliff is a second layer representing an older city, and farther down still a third layer, the remains of yet another city of vast and unknown antiquity.  Beneath the bottom city were recently found some specimens of glazed earthenware, such as are occasionally to be met with on that coast to this day.  I believe that they are now in the possession of Sir John Kirk.—­Editor.

“Quite so,” said Leo, “but that is not what you said before.”

“Well, what is to be done now?” I asked, turning the conversation.

As no answer was forthcoming we walked to the edge of the swamp, and looked over it.  It was apparently boundless, and vast flocks of every sort of waterfowl flew from its recesses, till it was sometimes difficult to see the sky.  Now that the sun was getting high it drew thin sickly looking clouds of poisonous vapour from the surface of the marsh and from the scummy pools of stagnant water.

“Two things are clear to me,” I said, addressing my three companions, who stared at this spectacle in dismay:  “first, that we can’t go across there” (I pointed to the swamp), “and, secondly, that if we stop here we shall certainly die of fever.”

“That’s as clear as a haystack, sir,” said Job.

“Very well, then; there are two alternatives before us.  One is to ’bout ship, and try and run for some port in the whale-boat, which would be a sufficiently risky proceeding, and the other to sail or row on up the river, and see where we come to.”