Pompeii

past the deserted baths her father was building, past the castellum aquae and under the arch of the city gate. She bowed her head as she passed the customs post, pulling the hood of her cloak low, and then she was out of Pompeii and on the road to Vesuvius.

Vespera

    [20:00 hours]

'The arrival of magma into the near-surface swells the reservoir and inflates the surface...'
Encyclopaedia of Volcanoes

    Attilius and his expedition reached the matrix of the Aqua Augusta just as the day was ending. One moment the engineer was watching the sun vanish behind the great mountain, silhouetting it against a red sky, making the trees look as though they were on fire, and the next it had gone. Looking ahead, he saw, rising out of the darkening plain, what appeared to be gleaming heaps of pale sand. He squinted at them, then spurred his horse and galloped ahead of the wagons.
    Four pyramids of gravel were grouped around a roofless, circular brick wall, about the height of a man's waist. It was a settling tank. He knew there would be at least a dozen of these along the length of the Augusta – one every three or four miles was Vitruvius's recommendation – places where the water was deliberately slowed to collect impurities as they sank to the bottom. Masses of tiny pebbles, worn perfectly round and smooth as they were washed along the matrix, had to be dug out every few weeks and piled beside the aqueduct, to be carted away and either dumped or used for road-building.
    A settling tank had always been a favourite place from which to run off a secondary line and as Attilius dismounted and strode across to it he saw that this was indeed the case here. The ground beneath his feet was spongy, the vegetation greener and more luxuriant, the soil singing with saturation. Water was bubbling over the carapace of the tank at every point, washing the brickwork with a shimmering, translucent film. The final manhole of the Pompeii spur lay directly in front of the wall.
    He rested his hands on the lip and peered over the side. The tank was twenty feet across and, he would guess, at least fifteen deep. With the sun gone it was too dark to see all the way to the gravel floor but he knew there would be three tunnel mouths down there – one where the Augusta flowed in, one where it flowed out, and a third connecting Pompeii to the system. Water surged between his fingers. He wondered when Corvinus and Becco had shut off the sluices at Abellinum. With luck, the flow should be starting to ease very soon.
    He heard feet squelching over the ground behind him. Brebix and a couple of the other men were walking across from the wagons.
    'So is this the place, aquarius?'
    'No, Brebix. Not yet. But not far now. You see that? The way the water is gushing from below? That's because the main line is blocked somewhere further down its course.' He wiped his hands on his tunic. 'We need to get moving again.'
    It was not a popular decision, and quickly became even less so when they discovered that the wagons were sinking up to their axles in the mud. There was an outbreak of cursing and it took all their strength – shoulders and backs applied first to one cart and then to the other – to heave them up on to firmer ground. Half a dozen of the men went sprawling and lay there refusing to move and Attilius had to go round offering his hand and pulling them up on to their feet. They were tired, superstitious, hungry – it was worse than driving a team of ill-tempered mules.
    He hitched his horse to the back of one of the wagons and when Brebix asked him what he was doing he said, 'I'll walk with the rest of you.' He took the halter of the nearest ox and tugged it forwards. It was the same story as when they left Pompeii. At first nobody moved but then, grudgingly, they set off after him. The natural impulse of men is to follow, he thought, and whoever has the strongest sense of purpose will always dominate the rest. Ampliatus understood that better than anyone he'd met.
    They were crossing a narrow plain between high ground. Vesuvius was to their left; to their right, the distant cliffs of the Appenninus rose like a wall. The road had once again parted company with the aqueduct and they were following a track, plodding along beside the Augusta – marker-stone, manhole, marker-stone, manhole, on and on – through ancient groves of olives and lemons, as pools of darkness began to gather beneath the trees. There was little to hear above the rumble of the