required for
overhauling the engine by curious spectators, who might even question
their right to be flying away from the front.

The landing was made in good style, and with only a few bumps, thanks to
the smooth character of the field's surface. Even Jack was compelled to
admit that though they had met with trouble, matters might be much worse.

"We'll get busy now, and soon have things as fit as a fiddle," said Tom,
throwing off some of his superfluous garments so as to be free to work.

By this time both boys had grown to be real experts in all sorts of
mechanical repairing, as every airman must of necessity become before he
can pass the acid test. Unlike the driver of a car on country roads, when
a break-down occurs he cannot step to a neighboring house, use the long
distance or local telephone, and summon help. The airman is usually
compelled to depend exclusively on his own ability to overcome the
difficulty.

To get at the seat of trouble necessitated considerable disarrangement
of the motor's parts. This consumed more or less time, and the minutes
passing were jealously given up by the impatient Jack.

But the boys worked fast, and finally all had been accomplished. Tom
tested the engine, and pronounced himself satisfied, while Jack looked
over the field ahead of them.

"It's going to take us to Dunkirk without any further trouble, I give you
my word for it, Jack," he said. "How long have we been here?"

"Just one hour, lacking three minutes," came the prompt reply.

"Then I'm safe," laughed Tom; "for I said within the hour. Come, pile
aboard and we'll be off. Sure you examined the ground ahead, and saw to
it we'd hit no bumps that might give us trouble?"

"It's all right there, Tom; could hardly be better. But be sure you don't
change from a straight course, because there's a nasty shell-hole, about
ten feet deep, to the left. If we struck that--good-night!"

"I notice you marked it with that pole, Jack, and I'll swing clear, you
can depend on that."

They had no difficulty in making a successful ascent. Once free from the
ground, the plane's nose was again turned toward the southwest. Tom had
long before marked out his course, and kept an eye on the compass as
well as on his little chart.

He knew they were heading for the Channel port as straight as the crow
flies. The sun was getting far down in the western sky, and it was now
necessary to shield their eyes when looking ahead, on account of the