The conversation dropped; other and more intimate topics anent the fair ones at home took its place; but in the mind of Percy FitzPercy the germ of invention was sown. When he went back to his battalion that night, in their so-called rest-billets, he was thinking. Which was always a perilous proceeding for Percy.

Now it so happened that his part of the line at the moment had originally belonged to the Hun. It was a confused bit of trench, in which miners carried on extensively their reprehensible trade. And where there are miners there is also spoil. Spoil, for the benefit of the uninitiated, is the technical name given to the material they remove from the centre of the earth during the process of driving their galleries. It is brought up to the surface in sandbags, and is then carried away and dumped somewhere out of harm's way. In reality it is generally stacked carefully in the trenches themselves, thereby completely blocking all traffic; which is by the way.

But after mining has been in progress for some time, and various craters have been blown and sapped out to, and after trench mortars have "strafed" consistently for many months and torn the original surface of the ground to pieces, the actual position of the trenches themselves becomes haphazard. They cease in many cases to bear the slightest likeness to the ordinary trenches of commerce; they become deep gorges in mountains of sandbags. I have sometimes wished that those officers who apparently write home to devoted bands of female workers asking for more sandbags would get in touch with me instead. I shall be delighted to let them have anything up to five million, all filled, by return; which is again by the way.

To return to Percy. In his part of the front sandbags grew like pebbles on a shingly beach; and from time to time fresh cuts off the trenches were opened to allow for further expansion in the sandbag family. The existing front line in one place had started life as a cut off the old trench, and had gradually been taken into use as a permanency, and it was at this point that he stumbled on the great discovery which was destined to cause all the trouble. How he first stumbled is not recorded; but early one morning Percy FitzPercy could have been seen like a terrier with his nose down a rabbit-hole, lying flat at the bottom of the trench, peering into a noisome and foul-smelling cavity underneath him.

"My dear old boy," he remarked, enthusiastically, to a brother subaltern, who was watching the proceeding coldly, "it's an old German dug-out; I'm certain it's an old German dug-out."

"I don't care a damn if it is," answered the other, without enthusiasm. "It stinks like a polecat, and is undoubtedly full of all creeping things. For heaven's sake, let's go and get something to eat."

Slowly and reluctantly Percy allowed himself to be led away, thinking deeply. Only the week before had the Hun attempted a raid and actually entered the trench close to the spot in question, and here was apparently a ready-made man-trap should he do so again. After breakfast he would explore his find; after breakfast he would himself set to work and labour unceasingly. As I have said, Percy FitzPercy meant well.

It is possible that lesser men might have been deterred by the unpromising results of that exploration. Descending gingerly through the hole, which had been widened sufficiently to allow of the passage, Percy switched his torch around the cavity he found himself in. Above his head long rounded timbers, side by side and touching one another, formed the roof, which was in good condition, save in the centre, where the blue sky shone through the hole he had entered by. In one corner stood a bedstead covered by a moth-eaten blanket, while all over the floor crumbling sandbags and old clothes and equipment gave it the appearance of a rag-and-bone shop. In one place the wall had fallen in, a mound of chalk filled the corner, and from a score of vantage points elderly rodents watched with increasing disfavour this unexpected human invasion.

Up above in the trench the disfavour was repeated in that picturesque phraseology for which Thomas is famous.

"Wot are you a-doing 'ere?" An incensed sergeant rounded a corner, and gazed wrathfully at three privates, each armed with a spade and wearing gas helmets. "Wot 'ave you got them 'elmets on for?" He approached the fatal hole, and recoiled slightly. "Gaw-lumme! Wot's that smell?"