At the moment there spread a sudden rosy glow directly below them. Both aviators thought they were over an exploding shell, although the vicinity had seemed altogether quiet.
There followed no explosion and the light winked out immediately. The roaring motor of the aeroplane drowned ordinary sounds, but Sanderson made his solution of the mystery plain to his mate.
"It's below us—the railroad bed. That's a locomotive. The fireman opened the draft and the flames shot out of the stack. Quick! We'll have to risk it! I'll put a bomb down that stack, if I have luck."
The aeroplane swooped. The bark of an anti-aircraft gun sounded above the noise of their motor. The train was an armored troop train bound for the front and the motor of the swooping aeroplane had been heard.
The flash of the shot, however, gave the pilot the course of the train. "The gun, Sandy!" shouted Lefevre. "I got a flash at the road. It's straight. We can rake every car. Surer than the bombs."
The advice seemed good. The explosions of the German gun fixed on the roof of a forward car was a decided help to the attacking airplane. Lefevre drove only a few yards above the ground and parallel with the flying train. The aviators were taking a great risk, for a pole or other obstruction might wreck them at any moment. But the opportunity to do serious damage to the enemy was not to be neglected. Sanderson turned the crank of the mitrailleuse, raking the train from the rear car to the locomotive as their aeroplane passed.
The rain of bullets did fearful havoc, even destroying the gun-crew on the car-roof, the Americans being untouched. But the train rolled on and the machine gun fouled.
Lefevre had driven so swiftly that they were now up with the locomotive. Unhooking his belt, Sanderson threw himself to the end of the seat nearest the thundering train, and with his automatic pistol shot both the engineer and the fireman, as well as the armed guard on the tender-tank.
The train ran wild as the airplane soared upward again. A few hundred yards further on there was a sharp curve in the road and Lefevre had caught sight of it in time by the dim beam of the locomotive headlight. The locomotive and every car left the rails at that curve and piled up in the ditch.
The horror of this wreck, the effect of their bombardment, shook Frank Sanderson more than he would have been willing to own.