said Jack. "The shells are rather small, to
judge by the damage they do. I wonder why that is?"

"Probably their gun, or guns, can't fire any larger ones such a long
distance, or else their airships can't carry 'em up above the clouds to
drop on the city."

"Then you still hold to the airship theory?"

"Well, Jack, I haven't altogether given it up. I'm open to conviction,
as it were. Of course I know, in theory, a gun can be made that will
shoot a hundred miles, if necessary, but the cost of it, the cost of the
charge and the work of loading it, as well as the enormous task of
making a carriage or an emplacement to withstand the terrific recoil,
makes such a gun a military white elephant. In other words it isn't
worth the trouble it would take--the amount of damage inflicted on the
enemy wouldn't make it worth while."

"I guess you're right, Tom. And yet such a gun would make a big scare."

"Yes, and that's what the Germans are depending on, more than anything
else."

"But still don't you think the French will have to do something toward
silencing the gun?"

"Indeed I do! And I haven't a doubt but the French command is working
night and day to devise some plan whereby the gun can be silenced."

"There go the aviators now, out to try to find the big cannon,"
observed Jack, as he gazed aloft.

Soaring over Paris, having hastened to take the air when the signal was
given, were a number of planes, their red, white and blue lights showing
dimly against the black sky. They were off to try to place the big gun,
if such it was, or discover whether or not some Hun plane was hovering
over the city, dropping the bombs.

As Jack and Tom hastened on, in the wake of the crowd, which was
hurrying toward the place where the latest shells had fallen, again came
a distant explosion, showing that the gun had been fired again.

"Fifteen-minute interval," announced Tom, looking at his watch. "They're
keeping strictly to schedule."

"Night firing is new for the big gun," said Jack. "I do hope they'll be
able to locate the cannon by the flashes."

"It isn't going to be easy," asserted Tom.

"Why not?"

"Because you can make up your mind if the Germans were afraid to fire
the piece at night at first for fear of being discovered, and if now
they are firing after dark, they have some means of camouflaging the
flash. In other words they have it hidden in some way."

"Well, I suppose you're right. But say, Tom, old man! what wo