The hammer rang once. A spark jumped off the anvil and did not go out. It waited. They followed.

It dropped into Fiddle's forge. Inkling had two tools: the tick-weight and the tally-peg. Beto had two: the even-rule and the key-tag.

"Four towns, and four tiny hammers," said Inkling. "Somebody mended there first."

"Try it and see," said Fiddle.

The cart's bell rang once, and the wheels began to turn.

The cart came to Brimwater, a town on a wide river. On one bank sat a new bell, big and dark and shiny. On the other bank stood the bell tower, empty.

"The bell came by road," said the ferryman. "Now it has to cross. But look."

He pointed at a post by the ferry. It said: NO MORE THAN 400 KG.

"How heavy is the bell?" said Beto.

Nobody knew. The market balance could only weigh twenty kilograms at a time. The bell was far too big to lift onto it.

"It looks smaller than our cart! I can name it," said Inkling. "Call it three hundred. Load it!"

A round green frog hopped onto the ramp in front of her. His name was Glug.

"Looking is not the same as knowing," said Glug. "If you guess wrong, the ferry sinks, and the bell goes to the bottom of the river."

Inkling's cheeks went hot. She had named it too soon again.

"How would we know for sure?" said Glug.

"What does the water tell you?" said Fiddle. She would not say more.

Beto stepped into the empty ferry. It dipped down a little. Inkling stepped in too. It dipped down more.

"How does it work?" said Beto. "The more it carries, the lower it sits."

A small white bunny in orange dungarees was sitting on the town see-saw. Her name was Evenly. A bear cub called Teeter rode the other end.

"Same on both sides, and it's level," said Evenly. "Level means equal."

She looked at the ferry. "The same mark means the same," she said. "If the bell makes the boat sit at one line, then anything that makes it sit at that same line weighs the same as the bell."

The town rolled the bell onto the ferry on planks. The boat sank low in the water.

Beto leaned over the side and scratched a line exactly where the water came.

Then he stopped. Just above his line was an older line, worn almost smooth. Beside it was a tiny scratched hammer.

"Five towns," whispered Inkling. "Somebody weighed something here too."

The bell rolled off again. Now the town filled the ferry with river stones, basket by basket.

A round yellow bean called Bop hopped on the ferry rail. "One more! That's one more," said Bop, every time a basket went in. He did not skip a single one.

The sun went down. Everyone was tired. Then Beto looked over the side.

His line was under the water. They had put in too much.

"Just call it four hundred," said somebody. "Let's go home."

Inkling wanted to say a number. She always wanted to say a number. This time she didn't.

"Not yet," said Inkling. "The same mark. Not nearly the same mark."

They lifted stones out, one at a time. Bop counted them back. At last the water just touched Beto's line, and stopped.

In the morning, Teeter weighed the stones on the market balance. "Put it on the pan and watch," said Teeter. Each basket went on one side. The twenty-kilogram weight went on the other. When the beam sat level, the basket was twenty.

Seventeen baskets were full twenties. The last basket was twelve.

A soft heavy loaf of bread rolled up. His name was Loaf.

"Ten ones make one ten," said Loaf. "Seventeen baskets is one ten and seven."

Seventeen twenties is three hundred and forty. And twelve more is three hundred and fifty-two.

"Under four hundred," said Beto. "By forty-eight!"

The ferryman nodded. The bell crossed the river. By noon it was ringing in its tower.

Fiddle let them draw a thin brass point in the forge: a scriber, for scratching a level line. It went on Inkling's belt.

"I won't tell you. It will," said Fiddle, when Inkling asked who had made the old marks.

The cart's bell rang twice, and the road ran home.

The spark dimmed to a warm dot and settled back on the anvil. The Green was just the Green again.

Back on the Green

Lan wanted to know how heavy her big shell was. Inkling floated a plastic tub in the washing-up bowl with the shell in it, and marked the line with her scriber. Then she took the shell out and dropped in marbles until the tub sat on the same line. Twelve marbles.

At the mending shed, Bà Tư's sewing basket sat on the bench. Its old handle had been mended with wire. Beside the mend was a tiny scratched hammer.

"I rode the cart once," said Bà Tư, "when I was eight. Somebody older rang the hammer for me."

Inkling mended the wheel of Lan's toy boat. Beside the mend, she scratched a tiny hammer. She did not write her name.

Then she walked to the anvil and rang the hammer, once, for Lan.

Tell the story back to someone. How did they weigh the bell? One day, someone will ring the hammer for you.