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."
