From a far point in the west came a low sound which swelled gradually into a crash like thunder. In a few moments came another, and then another and then many. They could see no smoke, no fire, and the very distance lent majesty to the sound.
John knew well what it was, the thudding of great guns, greater than any that had been fired before by man on land. Lannes turned ashy-pale.
"It's the cannon, the German cannon!" he said, "and that sound comes from France. The Kaiser's armies are already over the border, marching on Paris. Oh, John! John! all the time that I was predicting it I was hoping that it wouldn't come true, couldn't come true! You Americans can't understand! In your new country you don't have age-old passions and hates and wrongs and revenges burning you up!"
"I do understand. It must be a serious battle though. All the planes are now flying westward, and there goes the Zeppelin too."
"Which leaves us safe for the present. Besides, the twilight is coming."
CHAPTER VII
THE ZEPPELIN
The brilliant sunlight faded into gray, but the European twilight lingers, and it was long before night came. John and Lannes stood beside the Arrow, and for a while neither spoke. They were listening to the thunder of the great guns and they were trying to imagine how the battle was swaying over the distant and darkening fields. The last of the air scouts had disappeared in the dusk.
"The sound doesn't seem to move," said Lannes, "and our men must be holding their own for the present. Still, it's hard to tell about the location of sound."