Pompeii

she had swept back her hair as she mounted her horse, and the way she had dwindled into the distance, following the road he had set for her – to the fate that he, and not Destiny, had decreed.
    He passed through Neapolis and out into the open country again, into the immense road-tunnel that Agrippa had carved beneath the promontory of Pausilypon – in which the torches of the highway slaves, as Seneca had observed, did not so much pierce the darkness as reveal it – past the immense concrete grain-wharfs of the Puteoli harbour – another of Agrippa's projects – past the outskirts of Cumae – where the Sibyl was said to hang in her bottle and wish for death – past the vast oyster beds of Lake Avernus, past the great terraced baths of Baiae, past the drunks on the beaches and the souvenir shops with their brightly painted glassware, the children flying kites, the fishermen repairing their flaxen nets on the quaysides, the men playing bones in the shade of the oleanders, past the century of marines in full kit running at the double down to the naval base – past all the teeming life of the Roman superpower, while on the opposite side of the bay Vesuvius emitted a second, rolling boom, turning the fountain of rock from grey to black and pushing it even higher.

    Pliny's greatest concern was that it might all be over before he got there. Every so often he would come waddling out of his library to check on the progress of the column. Each time he was reassured. Indeed, if anything, it seemed to be growing. An accurate estimation of its height was impossible. Posidonius held that mists, winds and clouds rose no more than five miles above the earth, but most experts – and Pliny, on balance, took the majority view – put the figure at one hundred and eleven miles. Whatever the truth, the thing – the column – 'the manifestation', as he had decided to call it – was enormous.
    In order to make his observations as accurate as possible he had ordered that his water clock should be carried down to the harbour and set up on the poop deck of the liburnian. While this was being done and the ship made ready he searched his library for references to Vesuvius. He had never before paid much attention to the mountain. It was so huge, so obvious, so inescapably there, that he had preferred to concentrate on Nature's more esoteric aspects. But the first work he consulted, Strabo's Geography, brought him up short. 'This area appears to have been on fire in the past and to have had craters of flame...' Why had he never noticed it? He called in Gaius to take a look.
    'You see here? He compares the mountain to Etna. Yet how can that be? Etna has a crater two miles across. I have seen it with my own eyes, glowing across the sea at night. And all those islands that belch flames – Strongyle, ruled by Aeolus, god of wind, Lipari, and Holy Island, where Vulcan is said to live – you can see them all burning. No one has ever reported embers on Vesuvius.'
    'He says the craters of flame "were subsequently extinguished by a lack of fuel",' his nephew pointed out. 'Perhaps that means some fresh source of fuel has now been tapped by the mountain, and has brought it back to life.' Gaius looked up excitedly. 'Could that explain the arrival of the sulphur in the water of the aqueduct?'
    Pliny regarded him with fresh respect. Yes. The lad was right. That must be it. Sulphur was the universal fuel of all these phenomena – the coil of flame at Comphantium in Bactria, the blazing fishpool on the Babylonian Plain, the field of stars near Mount Hesperius in Ethiopia. But the implications of that were awful: Lipari and Holy Island had once burned in mid-sea for days on end, until a deputation from the Senate had sailed out to perform a propitiatory ceremony. A similar explosive fire on the Italian mainland, in the middle of a crowded population, could be a disaster.
    He pushed himself to his feet. 'I must get down to my ship. Alexion!' He shouted for his slave. 'Gaius, why don't you come with me? Leave your translation.' He held out his hand and smiled. 'I release you from your lesson.'
    'Do you really, uncle?' Gaius stared across the bay, and chewed his lip. Clearly he, too, had realised the potential consequences of a second Etna on the bay. 'That's kind of you, but to be honest I have actually reached rather a tricky passage. Of course, if you insist –'
    Pliny could see he was afraid, and who could blame him? He felt a flutter of