he suspected would be the case, he discovered that a very thin layer of
dust had covered the place after the explosion.

While there was not much of this, at the same time, it would allow a
pair of keen eyes to discover footprints, providing they had been made
_after_ the layer had settled.

Ned's chums watched his every move almost breathlessly. They immediately
understood what he expected to do, and while not very sanguine of
success, still they hoped for the best.

They saw Ned start to move slowly along. He continued to hold his light
close to the rock, and waved it slightly from side to side, as though
bent on covering as much ground as possible. But the fact that he did
advance showed them that he must be meeting with some success.

Another step did Ned take, then a third and a fourth. The boys began to
breathe freely again, for hope had once more taken root in their
breasts. They saw that he was showing confidence, as though he had no
longer any doubt of his ability to decide the enigma.

Even Jimmy remembered reading about the visit of the Queen of Sheba to
the wise Solomon, when he ruled as king, bearing a wreath of natural
flowers in one hand and another that was artificial, but so skilfully
done that no eye could detect the difference, and then asked him to
decide. The wise king had simply ordered a window to be opened, and a
lot of bees, searching for honey, soon settled on the right flowers.

That was the commonsense way in which Ned Nestor usually settled knotty
problems.

"The trail in the dust runs along the smaller passage, that does not
lead to the worked part of the mine," he said; "and so it's up to us to
hustle after the three men. So come on boys, and let's hope we get to
the open air soon!"

CHAPTER XI.

A SUCCESSFUL SORTIE.

The success which had attended Ned's efforts thus far encouraged the
scouts very much indeed. Little things often carry considerable weight,
especially when boys are concerned. Besides, there are times when even a
thistle down will point to the way the wind is blowing. And a small
success spelled greater things in store for them.

Accordingly, they all hurried as fast as the conditions would allow.
Fortunately, there were few obstructions in the way to give them cause
for trouble. Here and there they discovered a slight fissure, in which
Ned warned them to be careful not to catch a foot, lest they get a bad
wrench that might even amount to a sprain.

O