Carstairs shouted back something, but the planes were now too far apart for him to hear.  John saw that the Omnibus, despite her awkward look, was flying well and he also saw through Lannes’ glasses four aeroplanes bearing up from the east.  He did not say much until he had examined them well and had concluded that they were Taubes.

“Lannes,” he said, “German machines are trespassing on our air, and unless I’m mistaken they’re making for us.”

“It’s likely.  Just under the locker there you’ll find a rifle, and a belt of cartridges.  It’s a good weapon, and if the pinch comes you’ll have to use it.  Are your friends good shots?”

“I think they are, and I know they’re as brave as lions.”

“Then they’ll have a chance to show it.  The Omnibus carries several rifles and an abundance of ammunition.  She might be called a cargo boat, as there’s a lot of room on her.  I’m going to bear in close, and you tell Caumartin and the others of the danger.”

The Arrow swerved, came near to the Omnibus, and John shouted the warning.  Carstairs and Wharton instantly seized rifles and he saw them lay two others loaded at their feet.  With the prospect of a battle for life air-sickness disappeared.

“You can rely on them, Philip,” said John as the Arrow bore away a little, “but I don’t like the looks of one of those German machines.”

“What’s odd about it?”

“It’s bigger than the others.  Ah, now I see!  It carries a machine gun.”

“That’s bad.  It can send a hail of metal at us.  It’s lucky that aeroplanes are such unstable gun-platforms.  When platforms and targets are alike swerving it’s hard to hit anything.  We’re going to rise and dive, and rise and dive and swerve and swerve, John, so be ready.  I’ll signal to Caumartin to do the same, and maybe the machine gun won’t get us.”

John was quite sure that the Arrow could escape by immediate flight, but he knew that Lannes would never desert the Omnibus, and its passengers, and he felt the same way.  The subject was not even mentioned by either.

The German machines, approaching rapidly, spread out like a fan, the heavier one with the machine gun in the center.  John could see the man at the rapid firer, but he did not yet open with it.  The Arrow and the Omnibus were wavering like feathers in a storm and closer range was needed.  John sat with his own rifle across his knee and then looked at Wharton in the Omnibus scarcely a hundred yards away.  The figure of Wharton was tense and rigid.  His rifle was raised and his eyes never left the man at the machine gun.

“I forgot to tell you, Philip,” said John, “that Wharton is a great sharpshooter.  It’s natural to him, and I don’t believe the shifting platform will interfere with his aim.”

“Then I hope that he never has done better sharp-shooting than he will do today.  Ah, there goes the machine gun!”