The process had begun perhaps two hours before Pliny's mother first noticed it. A relatively small eruption had presaged the larger one that formed the cloud. Taller and taller the pine tree grew, propelled from its chamber and sucked up into the sky through convection. At its peak, it would reach a height of thirty-three kilometres. Pliny the Elder decided that this 'phenomenon' warranted further investigation. After taking in what he could from his lookout point he made up his mind to leave Misenum to draw nearer to its source. Earlier in the day he had given his nephew something to write. When he now asked him whether he wanted to accompany him, Pliny refused, insisting that he would prefer to stay behind with his mother in order to work. Pliny the Elder would go without him. He gave orders for a boat to be fitted out and was just leaving the villa when he received a written message from his friend Rectina, who lived beneath Vesuvius. Terrified, she was begging for his help, for there was now 'no escape except by boat'. It was then, Pliny recalled, that his uncle 'changed his plan and what he had begun as an intellectual pursuit he completed with all he had'. Admiral Pliny had the entire fleet at his disposal and launched the quadriremes—large, but surprisingly swift ships equipped with two banks of rowers, two men per oar—with the intention of bringing help not only to Rectina, but to as many on that populated shore as he could.
For several hours, the fleet held course across the Bay of Naples. Despite heading in the very direction whence others were now fleeing, Pliny's uncle was said to have been so fearless that 'he described and noted down every movement, every shape of that evil thing, as it appeared before his eyes'. To any sailors who survived to tell the tale of their admiral's fortitude, the chance of reaching land in safety must have seemed increasingly remote as they proceeded across the water. First ash rained down on them, then pumice, then 'even black stones, burned and broken by fire'. This was no hail storm. The fall of grey-white pumice is thought to have lasted eighteen hours in total. On average, it was falling at a rate of 40,000 cubic metres a second. By the time the quadriremes had come within sight of the coast, the pumice had formed island-like masses on the sea, impeding them from advancing any further. When the helmsman advised turning back, Pliny the Elder adamantly refused. 'Fortune favours the brave,' he said.
Although the pumice prevented them from reaching Rectina, they determined to put in where they could. Stabiae, a port town just south of Pompeii, lay about sixteen kilometres from Vesuvius. A contemporary image reveals the town's harbour to have had long elegant promontories, criss-cross balustrades, sand-coloured pediments and towering columns crowned with sculptures of men. By the time the fleet arrived here, the columns would have been mere shadows, with evening falling across the bay.
As ash and pumice continued to pour down, Pliny the Elder went to find a friend, Pomponianus, who had already stowed his possessions aboard a ship, 'set on flight if the opposing wind settled'. Pliny the Elder embraced him and requested a bath before joining him for dinner. 'Either he was content,' Pliny speculated later, 'or he showed a semblance of contentment, which was just as great-hearted.' As his host and his household watched flames leaping from the mountain and lighting up the night sky, Pliny the Elder told them that they were witnessing merely 'the bonfires of peasants, abandoned through terror, and empty houses on fire'. As if soothed by his own deception, he soon fell asleep. He was fifty-five years old, corpulent and had a weak windpipe. As the hot ash and pumice began to mount up on the pavement outside the doorway, his raw and narrow airwaves—call it asthma—for once proved to be a blessing. He might have been trapped inside had his noisy breathing not alerted Pomponianus' household to his continued presence inside the house. Rousing him from his bedchamber, they gathered to make a final decision as to whether to stay put or leave while they still could. The weight of the pumice and repeated earth tremors had now begun to cause buildings to collapse. If they remained in the villa they might be crushed. If they ventured outside, then the pumice could still throw other structures down on top of them. About two metres of it would fall on the town of Stabiae alone.
The inhabitants of Campania had felt the tremors for days, but they were used to these movements, this background noise. As Pliny observed, 'they were not particularly frightening because they were so commonplace'. Over sixteen years had passed since the last truly devastating earthquake had struck, demolishing temples, baths and municipal buildings in Pompeii and the surrounding towns. Some citizens had fled after that earthquake and vowed never to come back. More had stayed, only to witness their neighbours wander in a sort of madness, their livestock—over 600 sheep—dying as noxious gases permeated the atmosphere. It would not occur to the people of Campania to connect these events with the eruption that was now taking place. It must have been inconceivable that what was unravelling so quickly had been set in train so many years earlier.