Barcroft's machine was the last to leave the "Hippodrome's" launching platform, and the last but one of the raiding craft. It was still dark. The misty outlines of the nearmost biplanes could be just discerned as they rose swiftly and steadily above the invisible destroyers. The crews of the latter gave the airmen three rousing cheers as they swept overhead, but the tribute was wasted. The farewell greetings were drowned by the roar of the engines.
As dawn began to break Billy made a rather disconcerting discovery. His seaplane was now the last of the procession. It had been over hauled by the one from the "Cursus," and what was more she was slowly yet surely dropping astern.
It did not appear to be the fault of the engine. The timing and firing seemed perfect. The motor was running like a clock, yet the rest of the raiding aircraft, most of which he knew were usually slightly inferior in speed, were distinctly gaining.
With the growing dawn the four escorting battle seaplanes could be distinguished, two on either side of the long-drawn line of bomb dropping air-craft. It was the duty of the former to engage any hostile aeroplane that attempted to bar the progress of the latter. Armoured and carrying two light quick-firers they were more than a match for the German airmen, and the latter were fully aware of the fact.
"Hang it all!" muttered the flight-sub as he actuated the rudder-bar and tilted the ailerons in order to check a cross-drift and to increase the altitude. "It's getting jolly misty. Hope it doesn't mean fog."
The rearmost of the rest of the air-squadron was now almost invisible, the others entirely so. As a matter of precaution Barcroft took a hurried compass bearing, fervently hoping that the mist would clear by the time he reached his desired objective.
"We're odd man out, old bird!" he shouted through the voice-tube. "Keep your eyes skinned. I don't want to get out of touch with McKenzie if it can be avoided."
"It can't," replied his observer. "He's just been swallowed up by the mist."
"I'll climb higher still," decided Billy. "There must be a limit to this rotten patch of vapour."
For another ten minutes Barcroft held on his course. He could not be far from land, he decided. Already the leading raiders must have achieved their object, if it were possible to see their target, and were on their return journey. The chances of a collision in mid-air with one of the British seaplanes suggested itself. The idea was not an inviting one—the impact of two frail and swiftly moving objects at an aggregate rate of nearly two hundred miles an hour, and the sickening crash to earth. There would be some satisfaction in knowing that an enemy aircraft was destroyed in this fashion, but the possibility—remote, no doubt—of sending one's fellow airmen and oneself to instant destruction was a proposition for which the misty air was responsible.