"Must be one ahead," was the answer. "I fancy----"

Dick did not finish, for at that moment came a blast of air stronger
than any that had gone before. The Dartaway spun around, left the
railroad tracks, made a semi-circle, and then came back again. As it
made the final turn there was a crack like that of a pistol.

"What was that?" cried Tom. "Was it the engine?"

"No, it was one of the stays!" answered Dick. He glanced around. "The
right plane is giving 'way! Sam, let her down, as quick as you can!"

"On the tracks!" gasped the lad at the wheel.

"Yes-- anywhere-- before we tumble!"

The biplane was already out of control. Sam manipulated the rudders as
best he could, and likewise the ailerons, and the machine dropped in
several wild dashes.

"The train!" yelled Tom. "Look out for the express!"

There was another gleam of light along the railroad tracks. The
evening express was approaching, running at topmost speed, to make up
some lost time.

The biplane was coming down swiftly. It veered towards the woods
beside the railroad tracks. Then it took another wild turn and hung
directly over the railroad. The boys were speechless, not knowing what
to do. The light of the express train kept coming closer and closer.