n
about a minute. If you want to see an earthquake in a coal mine, just
come along with me! You'll see it, all right!"

The boys left the old tool house without spending any more time in
conversation, and hastened down the ladders to the lower level. On the
way down the last gangway they heard some one moving about in the
darkness, and then came a cry of warning.

"Stand clear! Stand clear!"

"That's Ventner's voice!" exclaimed Will.

"There's a blast going off in a minute!" the voice came again.

"Now we've gone and done it!" exclaimed Will. "After all the trouble
we've taken to make that fellow think we've left the country, we've let
him bump right into us. I wonder if he really has fired the fuse."

"Stand clear! Stand clear!" shouted the voice.

Almost before the words had died out, the explosion came, tearing more
than one pillar out of position and dropping a great mass of slate down
on the floor of the cross-cutting.

For a moment the gases which filled the chambers were overpowering. The
only wonder was that they were not ignited. The electric lights carried
by the boys shone dimly through the smoke of the confined place.

"There goes Ventner," whispered Will, pointing to a figure moving
swiftly through the half-light of the place.

"He's going to see what the shot brought down!" suggested Tommy.

The boys rushed forward in a little group. When they gathered at the
scene of the explosion, the detective was not there.

"If he got hold of the cash, he knew what to do with it all right!"
exclaimed Tommy. "He got away with it before we got a chance to see what
he had. Now we've got to catch him!"

"May as well look for a needle in a load of hay!" grumbled Sandy.

"Look here," Jimmie exclaimed. "There's a way to keep him shut up in the
mine if we do the right thing. This cross-cutting runs out to a gangway
on the north, and that, in turn, leads, of course, to the shaft. Now,
one of you boys duck out to the shaft and see that he doesn't get up.
You'll have to go some on the way there, because a man with two hundred
thousand dollars in his pocket will put up some running match!"

"I'm off!" shouted Tommy. "I know I can get to the shaft before he can!
He's too fat-bellied to run, anyway!"

Tommy started away at a swift pace, and the other boys closed in on the
gangway, Will alone stopping at the scene of the explosion.

"This gangway," Dick explained, "runs back into the mine for some
distance, but t