Not over forty miles, I should say, as the crow flies, Jack. I've never
been over the route, but it can be measured on this copy of the map."

"And that's the direct line we expect to cover, of course?"

"We'll head due east."

"And as it'll be densely dark when we start I guess we needn't mount to
ten thousand feet to pass over the enemy lines, eh, Tom?"

"There'll really be little need," came the reply, showing that the pilot
had already figured all this out. "At the same time we ought to keep far
enough out of range to avoid being struck by stray shrapnel."

"Will they bombard us, do you think?" demanded Jack.

"Oh, that's to be expected," said Tom indifferently. "You see the men
who man the anti-aircraft guns are constantly on the alert. They're
bound to hear the whirr of our propeller as we pass over, no matter how
high we soar. The searchlight will spot us out, and then they'll do
their best to make things uncomfortable for the pair of us. But the
chances are ten thousand to one against our being hit."

"You said our course would be due east, didn't you?"

"I'll change that assertion a bit, Jack; we start east after we're well
across the front, and away from the dazzling searchlight business. In
the beginning we'll point the nose of our big machine toward the north."

"So as to deceive the watchers, of course," remarked Jack.

"That's what the game is."

Jack's eyes sparkled. He was always proud of his chum's clever reasoning
powers, and believed Tom could hold his own with any one with regard to
mapping out a promising plan.

Their preparations completed, the two air service boys lay down to
secure a little rest. As they were not to start until some time after
midnight, Tom believed they should secure a few hours of sleep. The moon
was a late one, and would not rise, even with a midnight start, until
they were well back of the enemy lines.

An alarm-clock aroused them at the appointed time. Tom immediately
shoved the noisy thing under his blankets before it could wake up the
entire house, and set people wondering what was happening that any one
should want to be aroused at such an unseemly hour.

It was terribly black outside. Jack pressed his nose against the window
and took a look, even while hurriedly finishing his dressing. Tom had
taken the precaution to put a fresh battery in his little hand electric
torch, which he believed would prove to be worth its weight in gold.

Arriving at their dest