The trench which Michael’s company were to occupy for the next forty-eight hours was in the first firing-line, and to reach it they had to pass in single file up a mile of communication trenches, from which on all sides, like a vast rabbit warren, there opened out other galleries and passages that led to different parts of this net-work of the lines.  It ran not in a straight line but in short sections with angles intervening, so under no circumstances could any considerable length of it be enfiladed, and was lit here and there by little oil lamps placed in embrasures in one or other wall of it, or for some distance at a time it was dark except for the vague twilight of the cloudy sky overhead.  Then again, as they approached the firing-line, it would suddenly become intensely bright, when from the English lines, or from those of the Germans which lay not more than two hundred yards in front of them, a fireball or star-shell was sent up, that caused everything it shone upon to leap into vivid illumination.  Usually, when this happened, there came from one side or the other a volley of rifle shots, that sounded like the crack of stock-whips, and once or twice a bullet passed over their heads with the buzz as of some vicious stinging insect.  Here and there, where the bottom lay in soft and clayey soil, they walked through mud that came half-way up to the knee, and each foot had to be lifted with an effort, and was set free with a smacking suck.  Elsewhere, if the ground was gravelly, the rain which for two days previously had been incessant, had drained off, and the going was easy.  But whether the path lay over dry or soft places the air was sick with some stale odour which the breeze that swept across the lines from the south-east could not carry away.  There was a perpetual pervading reek that flowed along from the entrance of trenches to right and left, that reminded Michael of the smell of a football scrimmage on a wet day, laden with the odours of sweat and dripping clothes, and something deadlier and more acrid.  Sometimes they passed under a section covered in with boards, over which the earth and clods of turf had been replaced, so that reconnoitring aeroplanes should not so easily spy it out, and here from dark excavations the smell hung overpoweringly.  Now and then the ground over which they passed yielded uneasily to the foot, where lay, only lightly covered over, some corpse which it had been impossible to remove, and from time to time they passed a huddled bundle of khaki not yet taken away.  But except for the artillery duel that day they had heard going on that morning, the last day or two had been quiet, and the wounded had all been got out, and for the most part the dead also.