The glitter of those bursting shells stabbed through the smoke of their explosion with little, twinkling flashes, like the sparkle of innumerable mirrors heliographing messages of death. There was one incessant roar rising and falling in waves of prodigious sound. The whole line of battle was in a grayish murk, which obscured all landmarks, so that even the Tower Bridge was but faintly visible.
Presently, when our artillery lifted, there were new clouds rising from the ground and spreading upward in a great dense curtain of a fleecy texture. They came from our smoke-shells, which were to mask our infantry attack. Through them and beyond them rolled another wave of cloud, a thinner, whiter vapor, which clung to the ground and then curled forward to the enemy's lines.
"That's our gas!" said a voice on one of the slag heaps, amid a group of observers--English and French officers.
"And the wind is dead right for it," said another voice. "The Germans will get a taste of it this time!"
Then there was silence, and some of those observers held their breath as though that gas had caught their own throats and choked them a little. They tried to pierce through that bar of cloud to see the drama behind its curtain--men caught in those fumes, the terror-stricken flight before its advance, the sudden cry of the enemy trapped in their dugouts. Imagination leaped out, through invisibility, to the realization of the things that were happening beyond.
From our place of observation there were brief glimpses of the human element in this scene of impersonal powers and secret forces. Across a stretch of flat ground beyond some of those zigzag lines of trenches little black things were scurrying forward. They were not bunched together in close groups, but scattered. Some of them seemed to hesitate, and then to fall and lie where they fell, others hurrying on until they disappeared in the drifting clouds.
It was the foremost line of our infantry attack, led by the bombers. The Germans were firing tempests of shells. Some of them were curiously colored, of a pinkish hue, or with orange-shaped puffs of vivid green. They were poison-shells giving out noxious gases. All the chemistry of death was poured out on both sides--and through it went the men of the Midland Division.