is gun. Then
holding it as if it were a pistol, he reached in as far as he could and
fired both barrels.

The reports sounded dull and smothered, and as we listened my uncle
said:

"It is only a narrow passage, I think."

Then he was silent, for the reports were repeated ten times as loudly,
and went on reverberating again and again, from farther and farther
away, till they gradually grew indistinct and strange, for there was a
strange dull roar growing louder and louder till the echoes were
drowned, while the roar seemed to come on and on, till without
hesitation on anyone's part we turned and ran splashing out of the
stream to the shore, to escape from a dark rushing cloud which came
streaming out of the mouth of the cave with screams, hisses, and
whisperings, out and away down the narrow ravine till it seemed to be
filled with birds and bats, while a strange black-beetly odour assailed
our nostrils.

"No doubt about there being plenty of room, lads," said my uncle, as he
laughed at our scared faces, for the sudden rush out was startling.

"Is them owls, sir?" said the carpenter, staring.

"No, no," replied my uncle; "they are something of the goat-sucker
tribe--night-birds which build in caves; but a good half of what we see
are bats."

"Yes, I can see they're bats, sir, and the biggest I ever did see.
Well, they won't hurt us, sir?"

"No, but they're terribly afraid we shall hurt them," said my uncle.
"Well, Nat, what do you say? Shall we explore the underground river?"

I felt as if I should like to say, "No, I would rather not," but the
pride within me made me take the other view of the matter.

"Yes," I said, "of course," and the sense of unwillingness was forgotten
in the desire to laugh at the look of horror in Pete's face as he stared
appealingly from one to the other.

"You won't mind, Cross?" said my uncle.

"No, sir; I should like it," replied the man.

"Light the lanthorn."

"Shall we take our loads with us, uncle?" I said.

"Certainly. If the way through is short we shall want them at the other
side. If it is long we shall want some refreshments on the way."

"But suppose--" I began, and then I stopped.

"Suppose what?" said my uncle.

"Suppose the river does not pass through the mountain, but comes from
deep down somewhere."

"The more interesting the discovery of its hidden source, my lad. But
that is not likely. Look at the rock. What is it--granite or gneiss?"

"No,"