Presently the communication-trench ended, and the ration-party stumbled across a double line of narrow-gauge rails, part of the intricate system behind the lines. The track ran diagonally to the direction of the trench. To the left it led to and beyond the Army Service Corps dump at La Tuille. In the opposite direction it disappeared in the bowels of the earth, while a network of branch lines complicated the system. All through the hours of darkness, for several months past, heavily-laden trucks carefully covered with camouflaged canvas rumbled away from the lines to return empty ere dawn. Latterly the reverse conditions prevailed. Full trucks, each propelled singly by manual labour and with long intervals between the vehicles, proceeded towards the trenches but never reached them.
Subterranean works of an extensive nature were on the point of being completed. Every load of excavation was carefully taken miles to the rear in the dead of night, in order to baffle the enemy's aerial observers. So well guarded were these operations that even the men in the trenches were unaware of their nature, although many shrewd conjectures were not far out.
"Hallo, chums!" called out one of the ration-party as a truck hauled by three sappers rattled along. "How's your Channel Tunnel scheme getting along?"
"Fine!" was the reply. "Are you taking up any shares in the concern? There'll be a sharp rise very shortly, you know."
Another fifty yards and a word of command from Corporal Preston brought the squad to a halt. Out of the darkness came the sound of a hundred marching feet; then, almost invisible in their khaki uniform, a battalion of Australian infantry passed. It was significant that the men were in light marching order.
"By Gum! There's something up," whispered Selwyn. "Crowds of bombers and a whole crush of Lewis guns. Hallo! Here's more of them."
The progress of the ration-party was slow. A constant stream of infantry, swarms of transport of all conditions, clearly denoted that operations of more than minor importance were impending.
"There's enough to swamp our trenches," declared Malcolm. "Where on earth are they going to assemble?"
"That Sapper fellow evidently knew something when he talked about a sharp rise," said Selwyn. "And look! Tanks--crowds of them!"
Ambling along by the side of the tramway came a long line of armoured mastodons. The ground shook under the relentless pressure of the tractor bands, the air reeked with petrol fumes. Viewed in broad daylight the Tanks looked formidable enough; in the darkness, their weird outlines distorted by the misty atmosphere, they appeared like huge, grotesque monsters from another world.