The infantry up in front heard the machines hum and drone overhead, heard the rush and howl of the passing shells, the thud of the guns' reports, the thump of the high-explosive's burst. That, for a time, was all. For a good half-hour there was nothing more, no sign of the heavy attack they had been warned was coming. Then the gunfire began to grow heavier, and as the light strengthened, little dots could be seen circling and wheeling against the sky and now and again a faint and far-off _tat-tat-tat-tat_ came from the upper air. For if it was quiet and inactive on the ground, it was very much the other way in the air. Our reconnoitring and gun-spotting machines were quartering the ground in search of targets, the scout machines sweeping to and fro above them ready to drop on any hostiles which tried to interrupt them in their work. The hostiles tried quickly enough. They were out in strength, and they did their best to drive off or sink our machines, prevent them spying out the land, or directing our guns on the massing battalions. But they were given little chance to interrupt. Let any of their formations dive on our gun-spotters, and before they had well come into action down plunged our scouts after them, engaged them fiercely, drove them off, or drew them away in desperate defensive fighting. Gradually the light grew until the reconnoitring machines could see and mark the points of concentration, the masses moving into position, the filled and filling trenches; until the gun-spotters could mark down the same targets and the observers place their positions on the map. Then their wireless began to whisper back their messages from the air to the little huts and shanties back at Headquarters and the battery positions; and then.... It was the turn of the guns to speak. Up in the trenches the infantry heard the separate thuds and thumps quicken and close and run into one long tremendous roar, heard the shells whistle and shriek and howl and moan over their heads, saw the ground far out in front of them veil in twisting smoke wreaths, spout and leap in volcanoes of smoke, earth, and fire. Battery by battery, gun by gun, the artillery picked up and swelled the chorus. The enemy machines did little gun-spotting over our positions. If one or two sneaked over high above the line, it needed no more than the first few puffs about them from our watching Archies to bring some of our scouts plunging on them, turning them and driving after them in headlong pursuit. On the ground men knew little or nothing of all this, of the moves and counter-moves, the dodging and fighting high over their heads. Their attention was taken up by the ferocious fire of our artillery, and in waiting, waiting, for the attack which never came.