ed the spark, and the engine was practically
running "wild."

"I hope she isn't getting ready to blow up!" thought the youth, and he
gazed anxiously ahead. Smoke was issuing from the motor-boat, coming
from some over-heated oil.

He leaped to the next high rock, and then plunged boldly forward, soon
gaining the bow of the craft. At the stern the propeller was churning
the water into a white foam. The craft was trembling violently, and the
hum of the machinery gave full evidence of the power it was exerting.

Fortunately, Dave's knowledge of gasoline engines now stood him in good
stead, and without the loss of a second he turned off the supply of
gasoline and the electric spark, and thus allowed the engine to "die."
As the propeller slowed up and stopped, the water behind the craft
calmed down, and then the pounding on the rocks was reduced to a gentle
rub that did little but scratch the paint.

"Is she all right, Dave?" called out Roger, who stood on the rocks of
the bank watching proceedings with great interest.

"I think so, although it hasn't done the engine any good to run wild.
She's pretty well heated up, and the cylinders may be carbonized, or
something like that."

"What are you going to do--try to run her in here?"

"No, I'll not take the risk. I only wanted to stop the engine and get
rid of the risk of the boat blowing up."

"You ran a big risk doing it. She looked to me as if she might go up any
instant."

"She can't get out of here--the current holds her," went on Dave. "She
will be perfectly safe until Nat comes for her. I'd like to know where
he is."

"Phil and some of the others went off to see."

To save the boat as much as possible, Dave took two of the wooden
gratings of the flooring and tied them to ropes hanging over the sides.
In this position they acted as fenders, so that the rocks rubbed against
the gratings instead of the boat proper.

"I am afraid he'll have quite a job of it, getting her out into the
stream," said Dave, on coming ashore, and when he was putting on his
socks and the gaiters. "She'll have to back out against the current and
do a lot of turning."

"Maybe he'll have to get somebody to tow him out,--with a very long
line," returned Roger.

"If only Nat didn't fall overboard," said Dave.

In the meantime, Phil and some of the others had run up the stream a
distance. As they turned a point where there were several small islands
the shipowner's son set up a shout.