Frank was already on the move. He may have been sorely puzzled to account for this strange and unprovoked attack on them by the unknown party or parties concealed inside the base of the old windmill; but he also knew that the only thing for them to do was to get away from the danger zone.
A third shot was heard just about that time, and Pudge gave a groan, which naturally alarmed the other boys.
"Don't tell me you've been hit, Pudge?" called Billy, whose heart was in the right place, even if he did occasionally joke his stout chum when a rollicking humor seized him.
"No, not that I'm aware of," came the answer, "but every time I hear that gun go off it gives me a fierce start. This thing is even worse than falling in an aëroplane, and expecting to get smashed when you strike the ground."
"But we're getting along, remember," said Frank, meaning to encourage the other.
"And these bends on the dip help to hide us from those Germans back there in the bargain," added Billy, wishing to contribute his mite of consolation.
The French aviator said nothing, though he too must have realized that they were all in more or less danger should they expose themselves too rashly. No doubt, those enemies concealed back of the walls of the windmill base were watching eagerly to catch signs of their presence, and ready to send a storm of deadly missiles that way at the least invitation.
Despite his size, Pudge was really making a good job out of it. He could do things when he made up his mind to try hard.
They could hear him puffing dreadfully, and making a noise that Billy likened to the blowing of a porpoise as it wallowed in the billows.
"Every foot counts with us, remember, Pudge," said Billy, who was just ahead of the fat boy, turning his head to speak, for it was hardly wise to call out any longer and thus tell the enemy where to fire.
"Mine feel like they were made of lead and I can hardly drag 'em along after me," the other replied, mistaking the meaning of Billy's words.
"There goes still another shot; I wonder what they can be shooting at?"
Hearing Billy make this remark, Frank saw fit to answer him.
"I think they must believe we're still hiding somewhere about the seaplane, which is partly visible from the rise; and every now and then they take a snap shot to let us know they're on the job."