The thin air literally shook under the concussion of hundreds of heavy guns as the battleplane swung high over the opposing lines. A big "affair" was in progress—one of those furious exchanges of strafing that are airily referred to in the official reports as "an activity of some magnitude." Two mines had just been sprung, their positions marked by huge clouds of smoke and dust. But of the actual fighting none was visible to the crew of the battleplane. A dense haze hid the khaki and grey fighting men from view, although rifle firing and the rattle of machine-guns could be distinctly heard as the see-saw struggle for the possession of the newly-made craters continued with the utmost desperation.
So intense were the undulations of the atmosphere over the terrific cannonade that the battleplane rocked violently. Her wings, beating the disturbed air with tremendous speed, seemed hardly able to support the main fabric. While the flight over the scene of the fighting lasted the mechanical bird was plunging and banking like a ship in a heavy following gale. So severe was the strain that had any of the metal-work been the least defective the weakness would have shown itself with dire results. Even Blake gave vent to an exclamation of relief as the machine drew safely away from the disturbed area.
"The spires of Hasselt," declared Lieutenant Fauvart, when, half an hour later, one of many of the numerous Belgian towns appeared in view, showing up clearly in the slanting rays of the setting sun. "You see those forests to the north? Beyond them lies Olhelt. It is in a valley, with trees all around. Already the valley is in shadow. The time for vengeance is at hand."
Evidently vengeance was the uppermost thought in the man's mind. Both lads had been curious to know the reason for the Belgian's oft reiterated words, but with their typical English reticence had refrained from asking him for enlightenment.
"I am cold," exclaimed Fauvart a moment later. "A man who is cold cannot do his work well. I go and get my heavy coat."
"And he wouldn't take my advice before we started," thought Athol, as the Belgian slipped from his seat and disappeared within the fuselage.
"We are in sight of Olhelt," announced Fauvart to Dick, who was sitting on the floor by the side of the motors.
"Are we?" replied the lad. "Think I'll have a look out."
He made his way to the Belgian's vacated post, and, leaning over, took in the expanse of country far beneath. Blake was circling the battleplane, since it was yet too early to volplane to the work of destruction. At that immense height, and thanks to the almost total absence of sound, the battleplane was safe from observation from the earth.
"I feel like a stoker in a naval engagement," thought Dick as he returned to his post. "Nothing to see, and all up if anything goes wrong. Another ten minutes will see the job through."