第7章 The Six Strikes

She had six days of record by the end of the week, and six strikes on the tide curve that she had not seen before she plotted them, and once she had plotted them they were the whole of the week. She plotted them on a sheet of graph paper, because the laptop's graph was not the right graph, and because she wanted to see the thing in front of her in a form that could not be scrolled past. The six strikes, on the tide curve, in order: Fourteenth, at slack, at the lowest point of the tide. Fifteenth, at slack, at the lowest point. Sixteenth, at slack, at the lowest. Seventeenth, at slack. Eighteenth, at slack. Nineteenth, at slack. Every one of them at the lowest point of the tide, and every one of them at the same interval from the last, and every one of them at the same amplitude, and every one of them at the same pitch. Six days. Six strikes. A tide that ran at two and a half metres and a bell that rang once a day at the bottom of it. She sat at the table with the graph in front of her and the laptop open and the bell on the wall above her, and she thought about the mathematics of a thing that does not drift. A struck metal body has a pitch. A struck metal body of a given size, of a given thickness, of a given alloy, has a pitch that is fixed by its shape. A bell of twelve inches, of brass, of a particular profile, will ring at a particular frequency. The bell on her wall, if she had rung it, would have rung at a frequency she could have measured. She had not rung it. She did not ring it. But the tone in the water was at seventy-eight hertz, and a twelve-inch brass bell of the profile she could see on the wall would ring, at a distance, at a pitch close to that. She got up and went to the hall and lifted the sheet and looked at the bell. She did not ring it. She took it down and put it in a bag and carried it to the kitchen table and set it next to the laptop and sat in the chair and looked at it and listened to the record and played the file at half speed, and the tone came in at seventy-eight, and the harmonic at one hundred and fifty-six, and the interval held. She played the file a second time, at full speed, with the headphones off, and the tone came out of the laptop's speaker, and it was the pitch of the bell on the table, and the bell on the table did not move, and the tone went on, and the bell did not move, and the tone went on. She turned the laptop off. She turned it back on. She played the file. The tone came out of the speaker. The bell did not move. She put the headphones on and played the file again. It was a bell. At seven forty-one that night, on the seventeenth, at slack, at the lowest point of the tide, she stood in the hall with the headphones on and the laptop on the kitchen table, and the tone came in at seventy-eight hertz, and the second at one hundred and fifty-six, and the interval held, and the amplitude held, and she did not move, and the tone went on, and the bell on the wall did not move, and the tone went on. At seven forty-four the tone stopped. At seven forty-five the bell on the wall rang, once, under its dust sheet, and the dust sheet did not move, and the bell rang, once, and then it did not ring again. She took the headphones off. She sat on the floor of the hall. She looked at the bell. She did not touch it. At eight o'clock she got up and went to the kitchen and made tea and did not drink it, and sat at the table with the graph in front of her, and she looked at the six strikes, and she understood, for the second time, what the graph was telling her. The six strikes, plotted against the date, were not six days of a fixed interval. They were six days of a fixed tide. The tide came to its lowest point at seven forty-one on the fourteenth, and at seven forty-four on the fifteenth, and at seven forty-one on the sixteenth, and at seven forty-three on the seventeenth, and at seven forty-one on the eighteenth, and at seven forty-four on the nineteenth. The tide was coming to its lowest point, on those six days, at times that were earlier and earlier and earlier, by about two minutes a day. She pulled the tide table up on the laptop and looked at it. The tide table said that the lowest point of the tide, on those six days, was coming at seven forty-four, and seven forty-one, and seven thirty-eight, and seven thirty-four, and seven twenty-nine, and seven twenty-four. The tide table was right about the tide. The bell was not ringing at the tide. The bell was ringing at the tide table's wrong time. No. The bell was ringing at the tide's right time. The tide table was wrong. She put the graph on the wall, next to the other graphs, and she pulled the tide table up again, and she looked at the numbers, and she did the arithmetic, and the arithmetic said that the tide, on those six days, was running at a range that was one point nine metres below the predicted range, and that the prediction had been made by a model that had been run on data from the last forty years, and that the model had been calibrated to a datum that had been set in nineteen thirty-two, and that the datum had been corrected, in two thousand and eleven, by a factor of zero point four metres, and that the correction had been applied to the datum and not to the model, and that the model was still running on the uncorrected datum. She did the arithmetic a second time. The model was wrong by one point nine metres. She did it a third time. The model was wrong by one point nine metres, and the tide was running at the range the model said it would not, and the bell was ringing at the time the tide actually came to its lowest point, and the tide actually came to its lowest point, and the bell was ringing at the right time, and the model was wrong. She put the laptop down and sat in the chair and looked at the wall of graphs. She called Ellerby. "Ellerby, I need to see you." "Come in Monday." "I need to see the tide model." "It's on the drive." "I need to see the tide model that you ran for the baseline." "It's on the drive." "I need to see the datum you calibrated it to." "It's on the drive. It's the standard datum. It's the national standard." "It's wrong by one point nine metres." "Then the model's calibrated to the wrong datum." "Then the whole baseline is calibrated to the wrong datum." "Tamar, the datum's national. The datum's used on every site in the country. If the datum's wrong, every site in the country is wrong, and the Authority has not had a datum correction in forty years, and the Authority does not make datum corrections because datum corrections invalidate consent." "Then the consent is invalid." "Then the consent is invalid." "Then the report is invalid." "Then the report is invalid." "Then I can't sign the report." "No. You can't." She hung up and sat in the chair and looked at the wall of graphs, and she picked up the phone and called Deveril. "Deveril, I've found the datum error." "I know." "How." "The bell told me. The bell tells the datum. That's what the ledger was for. That's what the third column was for." "What's the third column." "What they left behind. The datum is what you leave behind, when you go up the steps and come down. You leave the way you measured the water, and you come back with the way it is." She hung up. She sat in the chair. She picked up the phone and called Ruan. "Ruan, I need to know something." "Ask." "The datum. The national datum. When was it set." "Thirty-two." "Who set it." "Two people. One from the office in Ildwater, one from the village. The village one set it. The office one wrote it down." "Was the village one a Saltwyke." "Yes." "Was the office one a surveyor." "Yes." "Do you know his name." "No. I know his family. Nobody writes the family name down." "Do you know the village one's name." "Yes." "Was it a man or a woman." "Neither. It was a child." Ruan hung up. Tamar sat in the chair with the phone in her hand and looked at the wall of graphs, and she put the phone down, and she got up, and she went to the kitchen, and she made tea, and she did not drink it, and she sat at the table, and she looked at the six strikes, and she understood, for the third time, what the graph was telling her. The bell was not ringing at the tide. The bell was ringing at the datum. And the datum was set by a child, in nineteen thirty-two, and the child had not been written down, and the datum had been written down, and the datum had been corrected by a factor of zero point four metres, and the correction had not been applied to the model, and the model was wrong by one point nine metres, and the bell was ringing at the right time, and the tide was running at the right range, and the model was wrong, and the consent was invalid, and the report was invalid, and the bell was ringing, and the bell had been ringing since the fourteenth, and the bell had been ringing, before that, and the bell had been ringing, before that. She did not know for how long. She picked up the phone and called Lowri. "Lowri, the datum. Nineteen thirty-two. A child set it." "I know." "How do you know." "Because I have the entry. It's in the harbormaster's tide tables. It's in the left column, under the date. It says, in the margin, one line, in a hand I don't recognise: the datum is set by the walk, and the walk is by the child, and the child does not remember the walk, and the walk is written down here, in case the child forgets, and the child forgets." "Read it to me." "Can't. It's not written in words. It's written in soundings. Nine of them. Nine numbers, and a name, and the name is not a name, the name is a direction." "What direction." "Up." She hung up. She sat at the table with the phone in her hand and the graph in front of her and the bell on the wall above her, and she looked at the six strikes, and she looked at the numbers, and she did the arithmetic a fourth time. The child had set the datum. The child had walked the steps. The steps were nine. The numbers were nine. The direction was up. And the tide, on those six days, had been running one point nine metres below the model, and the model was calibrated to the datum, and the datum was set by a child who did not remember the walk, and the walk was written down in nine soundings, and the nine soundings were the walk, and the walk was the datum, and the datum was wrong, and the bell was ringing at the right time. She got up and went to the hall and lifted the sheet off the bell and looked at the crack and looked at the rope's ring, and she put the sheet back, and she went out to the yard, and she sat on the step in the cold, and she looked at the bay, and she did not see the steps, and she did not see the bell, and she did not see the water. She saw the graph. She saw the six strikes. She saw the interval. She saw the amplitude. She saw the pitch. She saw the numbers. She saw the walk. ---