Pompeii exhibition: Robert Harris on the eruption of the volcano Afterwards, whenever they compared their stories, the survivors would always wonder at how differently the moment had sounded to each of them. A hundred and twenty miles away in Rome it was heard as a thud, as if a heavy statue or a tree had toppled. Those who escaped from Pompeii always swore they had heard two sharp bangs, whereas in Capua, some 20 miles distant, the noise from the start was a continuous tearing crack of thunder. But in Misenum, which was closer than Capua, there was no sound at all, only the sudden appearance of a narrow column of brown debris fountaining silently into the cloudless sky. For Attilius, it was like a great, dry wave which came crashing over his head. He was roughly two miles clear of the summit of Vesuvius, following an old hunting trail through the forest, descending fast on horseback along the mountain's western flank. The shock of the blast struck him from behind and knocked him forward. Hot air, like the opening of a furnace door. Then something seemed to pop in his ears and the world became a soundless place of bending trees and whirling leaves. His horse stumbled and he clung to its neck as they plunged down the path, both of them riding the crest of the scalding wave, and then abruptly it was gone. The trees sprang upright, the debris settled, the air became breathable again. He tried to talk to the horse but he had no voice and when he looked back towards the top of the mountain he saw that it had vanished and in its place a boiling stem of rock and earth was shooting upward. From Pompeii it looked as if a sturdy brown arm had punched through the peak and was aiming to smash a hole in the roof of the sky - bang, bang: that double crack - and then a hard-edged rumble, unlike any other sound in Nature, that came rolling across the plain. On the streets people were emerging to stare at Vesuvius, shielding their eyes, their faces turned towards this new dark sun rising in the north on its thundering plinth of rock. There were a couple of screams but no general panic. It was still too early, the thing was too awesome - too strange, too remote - for it to be perceived as an immediate threat. Up and up it went. The pillar, narrow at its base, was broadening as it rose, its apex flattening out across the sky. Someone shouted that the wind was carrying it their way. The crowd had become a solid mass as people streamed from the side streets to join it. Its back was to the mountain now, its face was to the sea, its single impulse: flight. Some screamed. Some sobbed. Most were tight-mouthed, intent on saving their strength for the battle at the bottom of the hill, where they would have to fight their way through the Stabian gate. A vast black wall of cloud was advancing towards the city, as dark as a storm. But it was not a storm, and it was not a cloud; it was a thundering waterfall of rock. Extracted from 'Pompeii' (Arrow') © Robert Harris 2003, available from Telegraph Books britishmuseum.org Follow Telegraph Art on Twitter