第15章 What Ellerby Wanted

The survey office was three floors up over a betting shop in the middle of town, and Ellerby had the air conditioning off and the windows open and a fan on a high shelf that moved the paperwork and not the air. He gave her tea in a mug with a chip out of the rim and asked her to sit down before he showed her anything, which she noticed, because nobody asks you to sit down before they show you something good. She did not sit down. "Sit," Ellerby said. "I'd rather stand, if that's all right." He nodded. He was a heavy man in his fifties who had been doing this work for twenty-six years and who had the particular calm of somebody who has watched a great many people tell him something he already knows. "The data's clean," he said. "That's the problem." "My data's clean." "Your data is clean," he agreed. "Nine days, no dropouts, no clipping, calibration within a tenth of a percent. That's better than most of what I get from the agency, and your kit is a decade old, which makes it worse." He turned the monitor toward her. "You've also got six minutes and forty-four seconds of something at the bottom of your band that my analyst says is a ferry." "There's no ferry within eleven miles." "She's made the same point," Ellerby said. "So let's go and see whether he's right, and in the order I'd go." He was not being cruel. He was being thorough, which was worse, because thoroughness is a thing you cannot argue with without looking like a person who has an interest in the answer. He laid out the four objections in the order he had them, and he wrote them on a whiteboard rather than reading them off the screen, and he wrote them in the flat unlovely hand of a man who has filled in ten thousand of these. One. Instrument self-noise, excluded by the reference channel, unless the reference channel is lying. Two. Acoustic coupling from the wall, and the wall was masonry and the wall was old and the wall had a bell in it, which everybody in Ebbmouth knew and nobody in that building cared about. Three. Shipping, and there was no shipping, and he had checked the AIS for every day of the record and could show her the plot if she wanted it. Four. Tidal compression noise, which is real, which is common on this coast in the hour either side of low water, and which has a signature like a struck bell if you do not know what you are listening to. "Four," Tamar said. "Show me four." He showed her four. It was a beautiful piece of work. It was on a second channel from a station at Ashenholt that had been logging since nineteen ninety-one, and it showed exactly what he said it showed, a low-frequency event every time the tide squeezed through the narrows, with the same strike interval, the same decay, the same partial at 156. "That's it," Ellerby said. "That's your bell. It's an acoustic artefact of a hard ebb through a narrow channel, and it has been in the Ashenholt record since before either of us was born, and it is the reason people have been hearing bells in this bay for two hundred years, and it is the reason that a nine-year-old boy walked up onto those steps in 1984 and came back able to tell his mother about a walk to a church that had been underwater for four hundred years." Tamar looked at the plot for a long time. "How many events," she said, "in the Ashenholt record?" "Four hundred and eleven." "How many coincide with a low water under minus one point nine?" "Every one of them." "Does that prove it?" "No," Ellerby said. "It proves you have a mechanism. A mechanism is the thing you have when you have an explanation, and the thing you have when you have an explanation is a thing somebody else gets to write." He uncapped the marker and put it in the tray and was quiet for a moment, and Tamar understood that he had got to the part he had brought her in for. "You've been at this eleven days," he said. "I've been at this bay thirty-one years. Let me tell you what the bay is. It's a drowned valley with a shelf in the narrows, and the shelf makes a low water about two metres below anything the Admiralty prints, and it has done that every spring tide since the ice left. That's not a secret. It's on the chart of 1861, in the corner where they put the little notes." "And the bell?" "The bell is in the corner," Ellerby said. "Read the corner." She had read the corner. It said, in the notation of a nineteenth-century surveyor: SOUNDINGS BY TRIANGLE. BELL NOTED IN SOUNDINGS, SOUNDING AS A SOUNDING. "He meant a sounding," she said. "He meant a sounding," Ellerby agreed. "He was telling the next man not to trust his lead line in the narrows, because there was something down there that would come up on it and take his depth. And every man since has read the word bell and thought of a church, and has never once thought of a rock with a hole in it that trips a lead." He turned the monitor back. "Now I'm going to ask you a question, and I want you to notice I'm not asking it as a favour to anybody, including yourself. What's your datum going to say?" "Minus two point one at the lowest event, and a tidal range that puts the working platform below the charted depth at the wall foot, which means the wall foot fails at design life, which means the consent is void and the money is spent and the scheme is finished." "You'd tell them that." "I'd have to file that." "You'd file that and they'd sack you." "Yes," she said. "Then file it," Ellerby said, "and I'll countersign it, and then nobody has to sack anybody and the file goes up and the truth is on the top of it where a journalist can find it in nine seconds." He leaned back in his chair and put his hands on his knees. "I didn't say that for your benefit," he said. "I said it because you're the first person in six years to bring me something that made me go back and look at the Ashenholt station, and I've been running that station for eleven years and I never once looked at the low water filter." "Did you look at it this morning?" "I've been in since half five," he said. "There's a woman downstairs who thinks I'm doing her drainage." ---