In the morning the canyon walls leaned together until they met overhead in a jagged vault of black magnet-stone, and the sound of the river rose from the floor to the roof.
Ysabet stopped just inside the cavern threshold, holding her tallow lantern high in her left hand while her eyes adjusted to the cool, greenish gloom.
Twenty feet above their heads, a broad underground river flowed upside down across the rock ceiling.
The water did not fall. Thick beds of dark, iron-heavy magnetic silt lined the arched roof, woven through with a dense, living mattress of hairy mineral-drinking tree roots that hung down from the mountain forest hundreds of feet above. Drawn upward by the lodestone arch and cradled in the tangled root-fibers, the current ran smooth and clear overhead like a ceiling of moving green glass. Pale, thumb-sized blind fish darted upside down among the root-strands, their bellies silver in the lantern light.
Beneath the suspended river, the cavern floor was dry pebble and packed grey clay, save for an occasional cold drop that detached from a root-tip and hit the stones with a hollow plink.
“The Upside Ford,” Sister Osha murmured, opening Mother Suth’s journal to check the map she had copied from Iskren’s parchment. “Iskren said the dry bed runs for two miles under the ridge. When the spring snowmelt doubles the current, the water fills the lower trough too, but in late autumn the magnet-silt and the iron-roots hold the whole channel aloft.”
