the scene of the second explosion. "But, Jack, do you know I shouldn't be surprised to learn that the shell was not from an airship at all."

"Where would it be from then?"

"The Germans may have massed such a lot of troops at some point opposite the French lines, that they have broken through and have brought up some of their heavy guns."

Jack shook his head.

"I don't believe they could do it," he said. "You know the nearest German line is about seventy miles from Paris. If they had started to break through, and had any success at all, the news would have reached here before this. And reinforcements would be on the way. No, it can't be. There must be some other explanation."

"But what is it?" asked Tom. "They've got to get nearer than seventy miles to bombard Paris. You know that."

"I don't think I really know anything about this war," said Jack simply. "So many strange, things have happened, so many old theories have been discarded, and so many new things have been done that we don't know where we are."

"Well that's true. And yet how could the Germans get near enough to bombard Paris without some word of it coming in?"

"I don't know. But the fact remains. Now let's get to where the second shell fell. Maybe we can see a fragment of it and—"

Once again the words were interrupted by an explosion. This time it was closer and the shock was greater.

"That's the third!" cried Jack.

"Yes," added Tom, looking at his watch, "and it's just half an hour since the first one fell. That indicates they're firing every fifteen minutes. Jack, there's something weird about this."