g of
a cave, covered with logs and heaped-up brushwood.

"Something more to investigate," said Tom, and began to pull the
brushwood away, followed by his companions. The logs followed, and
there was revealed to them an opening at least twenty feet square by
half that in height.

"What do you call this?" questioned Tom, as he kicked something of
metal lying under a pile of dead leaves.

"It's a roller of some sort," answered Songbird. "And see, here are
some cog-wheels and a lot of old shafting."

"Machinery, and quite some of it, too," murmured Dick. "They must
run a regular factory of some sort here."

"I think I have solved the problem!" cried Fred. "I've read of this
a number of times. This Sack Todd has a secret process of manufacturing
some article and he doesn't want anybody to learn what the process
is. So he has established himself here and sworn all his workmen to
secrecy."

"I've heard of that myself," said Tom. "A man had a certain process
of tanning leather. He kept his secret for years, until a workman
got mad at him and gave the thing away."

Dick was inspecting the machinery with care. It was worn out and
rusted, and hard to make out just what it was.

"Unless I am mistaken, these are parts of a printing press," said
the eldest Rover.

"A printing press?" cried several of the others.

"Yes. But that doesn't solve the mystery of what the press was used for."

It was damp and unwholesome in the cave, and they were glad enough
to leave it and come out into the sunlight once more. They walked
back to where they had left their horses, and here procured lunch,
and fed all of the animals, including Wags.

Slowly the afternoon wore away. It began to grow cloudy, and so became
dark at an early hour.

"We may as well start," said Dick at last. "We can go to the edge of
the woods, anyway."

"I suppose you don't know when you will be back," said Tom.

"No, but probably in three or four hours."

"Take good care of yourselves."

"We'll try to do that," put in Sam.

"If I were you, I'd not expose myself," was Fred's advice. "Those
chaps are rough customers, and there is no telling what they would
do if they caught you spying on them."

"That is true."

A few words more followed, and then Dick and Sam set off on their
tour of inspection. Each carried a pistol, and each felt that he
could take care of himself. But neither dreamed of the dire peril
which he was confronting.

They had left thei