The district changed the register in the last week of October. Nobody asked the sorting office whether it wanted a new register. It arrived anyway, in a cardboard folder, with a sheet of instructions that Merta read twice and then pinned to the wall face down.
The new rule was easy to say. Every letter now carried two stamps: a small blue square from the north window, a small red circle from the south. A letter was queried when it had exactly one of them. Both stamps meant the letter was fine. Neither stamp meant the letter was fine. Only the ones caught in between, one and not the other, went into the UNSURE box.
Merta put the first tray on the bench at six in the morning. By eight the box was full. Our uncle read the instructions, wrote eleven rules, crossed out six, and then did what he had learned to do in the counting house. He took out a sheet of graph paper and gave it to the man who kept the line.
The cousin drew the axes first: blue square across, red circle up. Then he marked the letters. The fine ones sat in two corners, bottom left and top right. The queried ones sat in the other two, top left and bottom right. He drew his line. It cut off one queried corner and let the other through. He moved the line. The second corner came in and the first went out.
He moved it thirty-four times before the first break. He moved it sixty-one times before the second. The youngest counted each move on her slate, in a column she had started the week before, and the number did not settle. It went up, it went down, it never stayed.
At last he put the pencil down. "There is no line," he said. "There is a word," said our uncle. "Either. Or. Not both." "A word is not a line," said the cousin. "I know," said our uncle. "That is the whole trouble with my side of the family."
The youngest took the chalk. She did not write blue. She did not write red. She folded the two questions into one and wrote the fold. A letter with a square and no circle became one thing. A letter with a circle and no square became the same thing. The other two kinds became a different thing.
On her page the four corners collapsed into two rows. One short line, drawn low, separated the rows cleanly, and the line did not have to move again. The cousin looked at it for a long time. Then he said the sentence we would hear for years. "Two questions asked at once are not the same as one question asked twice."
Merta made them show the shift. She would not accept paper. So they knelt on the sorting-room floor with a stub of blue chalk and drew it where everyone walked. Our uncle drew a line. The youngest drew a square around two corners. Merta looked at both and asked which one it was. "Both," said our uncle. "That is the problem." The shift stepped around the square all afternoon. Somebody chalked MIND THE CORNERS beside it, and nobody rubbed it out.
That evening our uncle opened a new page in the examples ledger and wrote PAIRS at the top. Under it he wrote one sentence: a rule can name a combination, but a line cannot learn one unless the combination is handed to it as a thing. Then he did what he had been doing all autumn, and passed the pen to the youngest so she could sign the page.
For ten years he had believed the difficulty was finding the right rule. Standing over that page, he said the difficulty was shape. Some truths have edges that can be cut with a line. Some have edges that only close in a corner.
Merta came by with her small notebook and her pencil behind her ear. The district would send someone in the spring, she said, to look at method and not only results, and the two stations would be measured against each other, river against mountain. "Then they will ask us which shape," said the cousin. Our mother, who had been listening from the door with her hands in her sleeves, looked at the chalk on the floor and said we would need both hands for that. One for the line. One for the corner.
The fire in the cold room was still going when the last post went out. The chalk faded where the shift walked, and the square became a smudge, and then a suggestion, and then the floor again. We kept the page instead. We did not know yet what a square was for. We only knew that a line was no longer enough, and that this was not a sadness. It was the first time the family had ever been given more room.
House of Sparks is a work of fiction. The family, the office and its people are invented. Real milestones appear only as weather, and no living person is depicted.