The oak balks groaned as Tomas Reed put his weight against the four-foot carbon steel crowbar.
Beside him, Renn Tal wedged a second iron bar into the gap, his boot heels digging into the black sand floor. The bolts holding the barricade had rusted through their washers. With a sharp, wet crack that sounded like a breaking pine branch, the middle timber snapped free. It swung outward on its lower iron pin to reveal an opening eighteen inches wide.
A blast of stale, white-hot air surged through the gap. He smelled intensely of rusted iron, hardened lime. The burnt-fat tang of scorched metal tube oil.
Tomas squeezed through first, his shoulders brushing the splintered wood. It was followed by Nessa and Tal with the lamps.
The chamber beyond was thirty paces square, directly beneath the central hearth of Blast Furnace Number Four. The walls were not made of ordinary red brick. They were lined with huge blocks of cream-colored heat-proof fire-clay, twelve inches thick, glass-fused into a smooth, glassy glaze by hundreds of years of intense heat. Overhead, massive cast-iron arch-ribs supported the huge deadweight of the blast fire above—four thousand tons of stonework, heat-proof lining, and molten iron ore resting on four main granite piers.
