ely harmless that an
uninitiated observer would almost invariably ask its use.

At the lower end of the launching tube, through which the bombs were
dropped, was a "trip," or sort of catch, that caught on a trigger
fastened to each bomb. The trip pulled the trigger, so to speak, and set
in operation the firing device.

In the early days, though doubtless the defect was afterwards corrected,
the bombs sometimes stuck in the launching tube, and as they were likely
to go off in this position at any moment, it was the custom of the
pilots to push them on their way with the cane if the missiles jammed.
Hence it was an essential part of each flying machine's armament.

Higher and higher mounted the fighting scouts, with Tom and Jack among
their number. It was necessary to mount very high in order to get
above the Zeppelins, as in this position alone was it possible for the
aeroplanes to fight them to any advantage. The Zeppelins carried many
machine guns of long range, and for the pigmy planes to attack them on
the same level, meant destruction to the smaller craft.

There were several German machines in the raid toward Paris, but Tom
and Jack caught sight of only two. The others were either at too great a
height to be observed, or else were farther off, lost in the haze.

But the two silver shapes, resembling nothing so much as huge, expensive
cigars, wrapped in tinfoil, were flying on their way, now and then
dropping bombs, which exploded with dull, muffled reports--an earnest of
what they would do when they got over Paris. They were traveling fast,
under the impulse of their own powerful motors and propellers, and also
aided by a stiff breeze.

Of course conversation was out of the question among Tom, Jack and the
other aviators, but they knew the general plan of the fight. They were
to get above the Zeppelins--as many of them as could--and drop bombs
on the gas envelope. They were also to attack with machine guns if
possible, aiming at the rudder controls and machinery. It was the great
desire of the Allied commanders to have a Zeppelin brought down as
nearly intact as possible.

Up and up climbed the speedy scout machines, and it was seen that some
of them would never get in a position to do any damage. The German craft
were traveling too speedily. But Tom and Jack managed to get to a height
of about twenty thousand feet, which was above the Zeppelins, though by
this time the Germans were in advance of them, for t