excitement. Looking down, Jack could detect moving lights, the source of
which he could only speculate upon. Then came a flash which must mark the
discharge of the first anti-aircraft gun. The enemy was showing exceeding
nervousness, for as yet the leading American plane could not be anywhere
within range.

With the burst of shrapnel there came a realization that the gunners
below were only trying to get their range. The whole pack would break
loose in another minute or less; but Jack had reason to believe their
altitude was such as to render the fusillade harmless.

Then down below he saw a sudden brilliant flash. That must mark the
falling of a flaming bomb, dropped from one of the big planes in order to
get a lead on their location. Jack believed he had even glimpsed the
bridge itself in that brief interval. How the prospect thrilled him!

Tom, on his part, had little opportunity to observe anything that was
taking place earthward. His duty lay closer at hand, for he knew that a
swarm of fighting Gothas had started up to engage the attacking squadron,
and realized that one or more of these hostile aircraft might suddenly
appear close at hand, bent on bringing about their destruction.

Besides, constant vigilance was the price of safety in other particulars.
With almost a dozen of their own planes speeding through space, a false
move on the part of a careless pilot was apt to bring about a collision
that could have only one result.

Jack made a discovery just then that caused him to cry out.

"The signal, Tom! We are to drop down and give the bombers a better