The barometer had been reading the same pressure for six hours, which was not possible.
Yseult noted it in the log with the time and her initials, then noted it again, and then set the pen down and looked at the instrument itself. Compact-issue, calibrated before departure, sealed against the damp of the threshold crossing. The needle sat at 1013 hectopascals as if it had been painted there.
Outside the survey station’s single window, the sky was doing several things at once. Clouds moved. The trees at the valley’s edge moved. A front was coming in from the west — she could smell it, that iron smell that preceded rain — and yet the needle did not move.
She picked up the pen and wrote: Instrument suspect. Cross-reference with portable unit requested.
Oswin came back from the ridge at the fourth hour of afternoon, boots wet to the ankle. He read the log standing up, the way he always did, holding it at arm’s length as if the distance made the information more legible. Then he looked at the barometer. Then at her.
“Still,” she said.
He set the log down and took the portable unit from his pack. It was smaller than the station barometer, less precise, meant for spot readings in the field. He held it level and waited.
987, it read.
The rain that had been threatening arrived then, not gradually but all at once, the way it always did in this world, as if weather here had no patience for its own transitions. Oswin watched the portable unit’s needle swing up through 990, 995. The station barometer sat at 1013 and did not acknowledge the rain at all.
“Right,” he said.
She had the service manual for the station unit out before he finished the word. Standard fault-finding procedure. She checked the vent, the float chamber, the temperature compensation mechanism. Everything was correct. Everything was seated and clean and correct.
Oswin stood at the window with the portable unit in his hand, watching it read the storm. She was aware of him doing this the way she was aware of most things he did — peripherally, precisely, without comment.
“The Reyes posting,” he said.
“I know.”
She had read the Reyes posting file twice before they came through the threshold, once on her own initiative and once because her section chief had handed it to her and said don’t let it make you superstitious. Senior Surveyor Reyes had filed a quarantine recommendation on this world eleven years ago. Her instrument logs were appended. Yseult had read them and understood, intellectually, that three of Reyes’s four recording instruments had gradually ceased to respond to present conditions and begun instead to log historical data — pressure readings from a storm that had passed through the valley the previous season, temperature records from a cold snap weeks before the survey team arrived. The instruments had not broken. They had, in some sense Compact science could not yet explain, remembered.
Reyes had quarantined the world on those grounds. Her recommendation used the phrase temporally adhesive substrate, which had been queried by the filing committee and left in the record unremarked.
The section chief had said: Your instruments will be newer. Better sealed. Keep your logs.
Yseult made a note in the log. She wrote: Station barometer non-responsive to present conditions. Cross-reference with portable unit confirms discrepancy of 26 hPa. Consistent with Reyes file, appendix C, day four. She paused. She wrote: Day three.
They were a day ahead of schedule, which she had thought was an advantage.
“Portable unit,” she said.
Oswin handed it over. She took a reading herself — 1001 now, the storm settling in — and handed it back, and wrote down 1001, and wrote down the time, and wrote down her initials.
“If it follows the Reyes pattern,” Oswin said.
“It may not follow the Reyes pattern exactly.”
“No.”
She capped the pen. The rain came hard against the window and the station barometer read 1013 and the trees at the valley’s edge were bending, distinctly, in a wind that was happening right now.
“We continue the survey,” she said. “We log everything. If the portable unit goes—” She stopped. “We log everything.”
Oswin took his wet boots off at the door and set them to dry. He did this with the same attention he gave most things, heels together, laces loosened properly. She had noticed early in the posting that he kept his kit in very good order, and had decided this was the kind of information that was useful about a person.
“What was the pressure reading,” he said, “on the day the Reyes team arrived.”
She knew without looking it up. “1013.”
He nodded. He set the portable unit on the table beside the station barometer and did not say anything else. She picked up the pen and opened a new page.