The Drowned Observatory

The buyer is a gray-haired scholar with spectacles perched on her nose. She breaks the wax seals immediately. "A mountain lake has no natural tides. This one was given artificial tides by an Old Kingdom pumping engine on its bed. Only when the wind dies completely does the water lie flat enough to spot the copper observatory dome beneath the surface. According to these tables, the next dead calm is only days away."

She hurries after you down to the dock, her arms overflowing with charts. "The dead calm is only days off—enough time for one errand, not two. Either carry me to the mountain lake by way of the Old Kingdom floodgate house that drains it, or deliver my delicate instruments to my college in the next region so someone believes my findings before scavengers strip the dome bare." She is seventy if she is a day, and entirely out of breath.

A squat stone gatehouse straddles the rushing stream that drains the high mountain lake. Inside stands an iron sluice wheel as tall as a man, paired with an Old Kingdom stone tablet listing how many turns lower the lake by how many feet. Fresh grease gleams on the axle, and a scavenger's tally is chalked on the wall. Opening the gate will drop the lake level until the observatory dome stands half-dry—though the rushing current will stir up the surface for a day.

A college porter signs for the padded crates and fetches a senior lecturer in a patched gown, who pries them open right on the cobblestones. "So she was right all along. For forty years the faculty laughed at her." He pays your freight fee out of his own purse rather than make you wait on the bursar, then looks up earnestly. "You spoke with her. Is she well? Is she still working alone up there?"

Every breath of wind has died, leaving the mountain lake as flat and clear as poured glass. Clearly visible beneath the surface sits a great copper dome with its observation shutters wide open. A scavenger barge is already moored directly above it with a diving bell swung out over the rail—and her crew are not pleased to see another ship arrive.

Precision survey gear hangs from every oak beam of the hall: spirit levels, brass azimuth rings, and a helm compass the size of a cartwheel. The master artificers look up from their workbenches as one. "We pay our trusted carriers in craftsmanship," the lecturer says. "What does your vessel require?"

The Old Kingdom built this chamber to study water pressure, not stars. At the center of the dome stands the machine that gave the mountain lake its artificial tides: a bronze pressure-pump with a muzzle like a siege mortar. Suspended in a gimbal cradle above it hangs a crystal lens as wide as a feast table.

The barge master is a patient veteran with a deep-sea diver's burst capillaries reddening his eyes. His diving bell goes down while your deckhands work the winches. By nightfall, a massive bronze water pump with a barrel like a mortar rests on his deck, beside a magnifying lens as wide as a table. "The pump came up in my bell, so the pump stays with me," he says. "The rest we split. Name your half."