China Focus: Chinese bamboo slips hold world's earliest decimal calculator

Bamboo slips dating back more than 2,300 years were officially recognized Sunday by the Guinness Book of World Records as the world's earliest decimal calculation tool.

"The significance is that it is decimal, not duodecimal as seen in other countries. Decimal did not appear in Europe until the 15th century," said Li Xueqin, head of the Research and Conservation Center for Excavated Texts at Beijing-based Tsinghua University.

The 21 slips, crafted around 305 B.C. during the Warring States Period, are 43.5 centimeters long and 1.2 centimeters wide each.

When arranged together as a multiplication table, the slips can perform multiplication and division of any two whole numbers under 100 and numbers containing the fraction 0.5.

The slips have inscribed numbers and holes, where threads used to go. A user would pull the threads corresponding to numbers needed to be calculated in order to see the result.

The owner of the slips remains unknown, according to Li. "Our guess is that the tool might have been used in trade or in the measurement of land in the kingdom of Chu," Li said.

PROTECTION, NO EASY JOB

In July 2008, Tsinghua acquired a rare collection of 2,500 slip bamboo items from the late Warring States period, which had been smuggled out of China, including the multiplication table.

"It was the day summer vacation started, and we had planned to take care of the bamboo slips after summer vacation," said Li. "When I opened the plastic box that held the bamboo slips, I saw they were quite muddy and I smelled harsh chemicals."

Small spots of mold were also growing on some of the slips. "If not immediately dealt with, the mold would have resulted in holes in the slips," said Zhao Guifang, an expert on bamboo slip protection at Tsinghua.

Li thought that they could wait no longer.

"As they are made of bamboo, they had actually become as soft and fragile as tofu after 2,300 years," he said.

He and his team of more than 10 people started cleaning the slips with the smallest and softest brushes. The team then spent the next four months cleaning the 2,500 slips day and night.

Cleaning was just the beginning. Preserving the slips also posed challenges for the team. In order to keep the slips in good condition, they had to put them in distilled water at a constant temperature and change the water very day.

The team now holds a meeting and reads the slips every Monday morning.

"Reading the slips is full of surprises and excitement, and I often get so excited that I have to stop by noon," Li said.

Apart from the multiplication table, the bamboo slips also have records of about 65 ancient texts that have been recognized to be among the most important artifacts from the Warring States Period.

"They have survived from the book burning of Qin Shi Huang, China's first emperor, who united the country. Therefore, they have great research value," Li said.

At the age of 84, he continues to be the protector of the bamboo slips. "There are still many slips that have not been read yet. I wish that I could read as many slips as I can to better protect them and push research ahead a step in the next decade," he said. Endi