She nodded, turning to face him. His eyes were closed.

"Let’s… take stock," he said slowly. "The city’s heading south. The Sorghum… Do you know what the Sorghum ’s for? The Sorghum, and the other rigs that I gather the Terpsichoria took you past, suck fuel from under the sea."

He spread his hands wide, indicating massiveness. "There are fields of oil and rockmilk and mercus under the earth, Bellis. You’ve seen the screwbores they use to plumb for the stuff on land. Well, geo-empaths and the like have found vast deposits under the rock, lying under the sea.

"There’s oil under southern Salkrikaltor. That’s why the Manikin and the Trashstar and Sorghum have been perched out there for more than three decades. The supports of the Manikin and Trashstar go down four hundred feet and sit on the bottom. But the Sorghum… The Sorghum ’s different." He spoke with a morbid relish. "Someone in Armada knew what they were doing, I tell you. The Sorghum sits on two iron hulls-submersibles. The Sorghum ’s not tethered. The Sorghum ’s a deepwater rig. The Sorghum can travel.

"You can just keep adding sections to its drill shaft, and it can go down Jabber fucking knows how far. Miles down. You can’t find oil and so on everywhere. That’s why we were stationary for so long. Armada was sitting over a field of something or other the Sorghum could get at, and we couldn’t move off until it had stored up for wherever it’s going."

How do you know all this?thought Bellis. What’s this truth you have to tell me?

"I don’t think it’s just oil," Silas continued. "I’ve been watching the flame over the rig, Bellis. I think they’ve been drawing up rockmilk."

Rockmilk. Lactus saxi. Viscous and heavy as magma, but bone cold. And dense with thaumaturgons, the charged particles. Worth several times its considerable weight in gold, or diamonds, or oil or blood.

"Ships don’t use fucking rockmilk to fire their engines," Silas said. "Whatever they’ve stockpiled for, it’s not just to keep their vessels trim. Look at what’s happening. We’re heading south, to deeper, warmer seas. I’ll bet you a finial we’re skirting close to ridges beneath, where there are deposits, a route that lets the Sorghum drill. And when we get wherever we’re going, your friend Johannes and his new employers are going to use… what, several tons of rockmilk and Jabber knows how much oil to do… something. By which time…" He paused, and held her gaze. "By which time it’ll be too late."

Tell me, Bellis thought, and Silas was nodding as if he had heard her.