"It could have come from an immense airship, so high up as to be beyond observation," suggested Jack. "That's possible. Probably the Germans didn't want to be bombarded themselves by aircraft guns here, and they flew high."
The police officer shook his head. He was not convinced.
"But, man, how else could it be?" asked Tom, in some heat. "The Huns have to rest their gun somewhere, and you—Say, Jack!" he suddenly exclaimed, his face paling slightly, "you don't suppose they have broken through, do you?"
"Through our lines about Paris? Never!" cried the police officer. "They shall not pass! Our brave soldiers have said it, and they will maintain it. They shall not pass!"
"And yet," mused Tom, as he looked at the rescue work going on, "what other explanation is there? It's a bombardment of Paris all right, by German shells. If they don't come from an aeroplane, high up, they must come—"
His words were drowned by another great concussion, but farther off. The ground trembled, but there was no sign of flying debris.
"Another!" cried the gendarme. "There goes the gun again!"
"I didn't hear any gun," observed Jack. "What we heard was the explosion of the shell. Look up, Tom, and see if there's a Hun plane in sight.
