The section of the train with the boys aboard had become a runaway
freight!

"What has happened?" cried Mark.

"The train's broken in two!" shouted Jack. "Come on! Help twist the
brakes!"

Both boys sprang to the wheel of the gondola. It was all they could do
to give it a few turns, but they managed to make the brake-shoes grip
the wheels to some degree, as was evidenced by the shrill shrieking.

"Can you climb up to the top of the box car?" asked Jack.

"Sure!" shouted Mark. "Go ahead!"

Though Mark was thin, he had a nervous strength almost equal to that of
his stouter companion.

"We must set all the brakes we can!" Jack cried. "That's the only way to
stop the runaway train!"

With their small arms they twisted the wheel on the box car. They got it
as tight as they could, then ran along the top of the vehicle to the
next one. About ten cars down they saw their friendly brakeman.

"That's the stuff, boys!" he shouted. "There'll be a smash-up if we
don't stop the cars!"