I do not know why, but some curious sense made one keep low in ducking round to a bay of the front trench. The enemy's reply was not due for some minutes yet. There was a sudden lurid red glare with a heavy crash over the parapet to our right--perhaps 150 yards away. "That's not one of their 5.9's, surely?" exclaims a friend. "One of our trench mortars, I think," says another. As we sit in the narrow trench, with our knees tucked up to our chins, there is no doubt whatever of the advent of a new sheaf of missiles through the air above our heads. We can hear the swish of our own shells, perhaps 100 feet up, and the occasional rustle of some missile passing overhead a good deal higher than that. One knows that this must be one of our howitzer shells making his slow path, perhaps 200 or 300 feet above us, on his way to fall on some German communication trench, and blow it in. I do not know, but I rather suspect his duty is so to jumble up the walls and banks of that trench as to prevent German supports from reaching their front line without clambering into the open fields where our shrapnel is falling like hail. But under those two streams of overhead traffic is a third quite easily distinguishable. It comes with short, descending screams--sheafs of them together. At the end of each there is a momentary glare over the sandbags, and the bang as of an exploding rocket. That is German shrapnel, bursting in the air and projecting its pellets in a cone like a shot-gun. A little to the south of us there is a much more formidable crash, always recurring several times in the minute. We always know when that crash is coming by a certain fierce orange glare which lights up the tops of our sandbags immediately before we hear the sound. Three or four times the crash and the glare came together, and a big cloud of stuffy-smelling white smoke drifted low overhead, and bits of mud and earth cascaded down upon us from the sky above; and just for two minutes the sheaf of four shells from some particular field battery, which sent them passing as regularly as a clock about five times a minute overhead, seemed to lower and burst just above us; and one or two odd high-explosive bursts--4.2, I should say--crept in close upon us from the rear, while the parapet gave several ponderous jumps towards us from the other direction. One would swear that it had shifted inwards a good inch, though I do not suppose it had. The dazzling orange flashes and crashes close around us were rather like a bad dream. One could not resist the reflection that often comes over a man when he begins his holiday with a rough sea crossing, "How on earth did I ever imagine that there was advantage to be obtained out of this?"