1Now turn your face to the east, as far as the land goes.
2While Rome ruled the lands around the inner sea, another empire ruled the lands of the Yellow River, and it was every bit as great. Neither knew much of the other. The eastern empire was called Han. Its ruler was called the Son of Heaven.
3That title was not an idle one. The people of Han held that the emperor stood between the sky and the earth, and that when he ruled badly the world itself gave signs of it. The sun was eaten. Stars fell. Worst of all, the ground shook. When the ground shook, every man at court looked sideways at every other, and asked whose fault it was.
4In the capital city of Luoyang there was a boy named Wen, fourteen years old, an orphan of no family. He had been taken on as a servant at the terrace where the sky was watched. He trimmed lamps and ground ink and swept the frost from the bronze instruments before dawn. He had not expected to love the work, and he did.
5The master of that terrace was the Chief Astronomer, an old man named Zhang Heng.
6Zhang Heng could have been a great lord. He was famous through the empire as a poet when he was young, and offers came to him from powerful men. He turned them down for years and read mathematics instead. When at last he took a post, it was this one: to watch the heavens, keep the calendar, and record the signs. It was not a high office. He held it without promotion for so long that people laughed at him, and he wrote a calm reply to the laughers and went on working.
7He had counted the stars and mapped them, two and a half thousand of the bright ones. He held that the heavens were round like an egg, and that the earth lay inside them like the yolk, small, in the middle of a vastness. He said the moon had no light of its own. It was a ball, and it shone only on the side the sun struck, and it went dark when the earth's shadow fell across it.
8He had built a globe of bronze rings, taller than a man, with the stars marked on it. Water dripping from a tank turned it, exactly as fast as the sky turns. Wen's first task each night was to stand inside the shut room with the globe and call out which star was rising on the bronze. A man on the roof would call back which star was rising in the sky. They were always the same star. The first time, Wen's skin had prickled all over. The sky was doing what an old man's water wheel said it would do.
9But the thing in the terrace that Wen was most afraid of stood in a hall by itself.
10It was a great jar of fine bronze, as wide as a man lying down, with a domed lid. Around its shoulder were eight dragons, heads downward, facing the eight directions. Each dragon held a bronze ball loosely in its jaws. Beneath each dragon squatted a bronze toad with its mouth wide open, looking up.
11Inside the jar, where no one could see, was a hanging weight and a set of levers. Only the master and one bronze-founder knew the way of it. The master said that when the earth shook anywhere, even far off, even too faintly for a man to feel, the weight inside would stir. One dragon would open its jaws. One ball would drop into one toad's mouth with a clang. And by which dragon had let go, you would know in what direction the earth had moved.
12The court had come to look at it when it was new. They had not believed a word of what it was for.
13For the master had enemies. The emperor of that time was young, and the true power in the palace lay with the servants of the inner court, who had put him on the throne. They were quick, proud men, and they had the emperor's ear at all hours. Once the emperor had asked Zhang Heng, before everyone, who in the empire the people most hated. The inner servants had fixed their eyes on the old man until he gave a careful answer that named no one. They had not forgiven him for what he might have said.
14And now he had built a thing that claimed to know about earthquakes. Earthquakes were not a matter of bronze and levers. They were heaven's judgment on the court. To say you could catch one in a jar was either foolishness or something more dangerous.
15Wen had the night watch in the hall of the jar. For two years he sat there with a lamp and a brush, and wrote in the record each dawn: nothing. The dragons held their eight balls. He grew used to them. He named the western one Old Sour, for its expression.
16In the second winter, on a still night with no wind, he was nodding over the lamp when the hall rang like a struck bell.
17He was on his feet before he was awake. The sound hummed away into the roof beams. He held up the lamp. Seven dragons had their jaws shut. Old Sour's mouth hung open, and the toad beneath it had a bronze ball in its throat.
18Wen stood very still. He felt the floor through his thin shoes. Nothing. The lamp flame stood straight up. The water in the wash bowl was flat as a mirror. Out in the city not a dog was barking.
19He ran for the master.
20Zhang Heng came in his sleeping robe with his white hair loose. He looked at the open jaw and the swallowed ball. He put his palm flat on the floor, then on the side of the jar. He asked Wen three questions. Had he touched it? Had anyone come in? Had he felt anything at all? No, no, and no.
21"West," said the old man. "A little north of west." He was already calling for his brush. He did not seem glad. Wen had expected him to be glad.
22At the morning audience Zhang Heng reported that the earth had moved in the west. He asked that fast riders be sent out along the western road at once, to find out where, and that grain and physicians be made ready.
23No one else in the capital had felt anything. Not one tile had slipped. The inner servants smiled behind their sleeves. One of them, a tall man with a soft voice, asked whether the Chief Astronomer wished the Son of Heaven to empty his granaries every time a toad was fed.
24The riders were not sent. The emperor said they would wait and see.
25That was the first day. On the second, the story was all over Luoyang, and it had become a joke. People in the market croaked like toads when the terrace servants went by. On the third day it stopped being a joke. A memorial was laid before the throne. It said that the Chief Astronomer had made a false report of an omen. To announce an earthquake where there was none was to say that heaven was angry with the emperor when it was not.
26On the fourth day two officers came to the terrace for Wen.
27The tall man with the soft voice was waiting in a side room of the palace. He was very kind. He gave Wen a sweet rice cake. He said that everyone knew how it was, on a long cold watch. A boy dozes. A boy stumbles in the dark, and puts out a hand to steady himself, and a ball falls. Then the boy is frightened, and tells his master he did not touch it. Nobody would blame a child for that. The child had only to say so now, and he could go home.
28"And my master?" said Wen.
29"Your master would be shown to have been mistaken. An old man's mistake. It would be the gentlest way out for him, too."
30Wen was not a fool. He saw that it would not be gentle. If the jar had been knocked by a servant, then the jar was a toy, and the Chief Astronomer had troubled the throne over a toy. He also saw the two officers at the door, and the bamboo rods they carried, and he knew what came after the rice cake.
31He had nothing in the world. No family, no name, no one who would ask after him. He had a mat at the terrace and a brush. And he had a line in the record, in his own hand, with the hour written beside it. It said the western ball fell at the third watch and that no one touched it. That line was true. It was the only thing he had ever made that was his.
32"I did not touch it," he said.
33They beat him. It will not be dwelt on. They asked again and he said the same, and they beat him again, and then they sent him back to the terrace on a board, as a message.
34Zhang Heng put salve on the boy's back with his own hands. They were an old man's hands and they were not steady. "You could have said you stumbled," he said. "I would not have thought less of you. You are fourteen."
35"It would not have been true," said Wen into the mat.
36"No." The old man was quiet for a time. "I will tell you what frightens me, since you have earned it. It is not the memorial. It is that I may be wrong. I have gone over the mechanism in my head for four days. I do not know why that ball fell. I know only that it did. I have told the court more than I know, and you have bled for it."
37"Then why did you tell them at all?"
38"Because if it is true," said Zhang Heng, "there are people lying under their own roof beams in the west tonight, in the cold. And it is four days already."
39On the fifth day the old man put on his court robes and went to the palace to answer the memorial. He took the night record with him. He said to the officials: "The boy did not touch it. I have his writing and I have his back. If the instrument is false, the fault is in my bronze and my reckoning, and I alone will answer for it." Then he waited outside the hall with the other men who were waiting to learn what would become of them.
40Wen could not stand yet. He lay on his stomach in the hall of the jar, because he had asked to be put there, and watched Old Sour's open mouth.
41Late on the sixth day, near dusk, there was a noise at the west gate of the city.
42A rider came in on a horse that was nearly dead. He came from Longxi, in the far west, more than a thousand li away. On a night six nights before, at the third watch, the earth there had opened. Towns were down. Hillsides had slid into the valleys. The dead were not yet counted.
43They say the court was silent for some time after he spoke.
44Then every man in it turned and looked toward the terrace of the sky, where a bronze jar had known it within the same hour.
45The grain wagons left the next morning, and the physicians with them. The tall man with the soft voice found that he had business elsewhere. An order came down that from then on the terrace was to record from which direction every earthquake came.
46That night the master sat beside him on the floor of the hall, under the eight dragons.
47"Six days," Zhang Heng said. "The wagons will be eight more on the road. Fourteen days in winter, with no roof." He rubbed his eyes. "If they had gone when the ball fell, it would have been eight."
48"They will go when the ball falls next time," said Wen.
49"Yes. That is something."
50Wen turned his head on the mat. "Master. The court says an earthquake is heaven's anger. You have made a jar that hears one coming over the ground like a cart. So which is it? If it is a thing of the earth, like the rain, then no one caused it. And no one can stop it. Not the emperor, not you. What use is it to know?"
51The old man did not answer for a while. The lamp burned between them.
52"I have watched the sky for forty years," he said. "In all that time I have not moved one star. Not by a hair. I cannot hurry the moon or hold off an eclipse. The Son of Heaven cannot either, whatever is said, and I think in his heart he knows it." He nodded at the jar. "And I cannot hold the ground still. No one ever will. If I thought my work was to command those things, I would have died of grief long ago."
53He lifted the bronze ball out of the toad's mouth. He weighed it in his palm, and set it back between the western dragon's jaws, and closed them with a click.
54"But where the wagons go, and how soon. That is not the sky's business. That is ours. I cannot stop the roof from falling in Longxi. I can make it six days sooner that someone comes to lift it. It is a small corner of the matter. I have found that it is the only corner where anything I do counts for much, so I try to keep it swept."
55"It is a great ease," he said, "to know which things are too big for you. You can stop shouting at them."
56The inner servants did not forget. Within a few years they had the old man sent away from the capital, to keep order in a far province under a lawless prince. He came home worn out and died soon after. He was sixty-one.
57His jar was lost in the wars that came later. No one now knows for certain how the inside of it worked, though many have tried to build it again. For seventeen hundred years no one anywhere made another instrument that could do what it did.
58Wen kept the night record at the terrace for fifty years. He wrote nothing, most dawns. But eleven times in his life he wrote a direction and an hour. And each time the wagons were on the road before the riders came in.