For decades, China’s middle school students were introduced to the world’s first seismograph through an image in their history textbooks: a large, bronze urn with eight dragons perched the same distance apart along the outside, each with a copper ball hanging precariously in its mouth. Whenever there was a tectonic tremor from a particular direction, the corresponding dragon would drop its copper ball into the gaping mouth of a frog perched below it — or so students were taught.

But for a new history textbook being used in public school classrooms across the country this fall, the image of China’s iconic earthquake detector and its accompanying text were removed, according to a Tuesday report by Huaxi City Daily that was later reposted by state-run China News Service.

On Wednesday, the textbook’s publisher, People’s Education Press, explained that the content had not been deleted, but rather moved to a different section. Sixth Tone confirmed from screenshots that the text about the seismograph had indeed been moved to a later section of the book — but the image was missing.

The seismograph is widely believed to have been invented by Zhang Heng, a scholar and polymath who was born in the first century A.D. during the Eastern Han Dynasty. The device is included in a biography of Zhang written a few centuries after the scholar’s death: In fewer than 200 characters, the author describes the seismograph’s appearance and claims it successfully detected an earthquake in northwestern China.

For decades, the popular conception of Zhang’s seismograph came from a 1951 model by the historian Wang Zhenduo, based on the description in the ancient biography. This image was added to China’s textbooks, but in most cases without a caption explaining that it was merely a scholar’s artistic interpretation. It became so commonly accepted that even U.S. President Richard Nixon was shown a seismograph model based on Wang’s during his historic visit to China in 1972.

However, the 1951 model’s fame and ubiquity have worried seismologists, who aren’t convinced that the design holds scientific weight. Most notably, it failed to detect tremors that could have predicted a devastating earthquake in 1976 that killed hundreds of thousands of civilians and rescue workers.

According to Huaxi City Daily, Feng Rui, a researcher at the China Earthquake Networks Center (CENC) under the central China Earthquake Administration, had been trying to persuade People’s Education Press to remove the image from its textbook. Feng could not be reached on Friday, but his colleague at CENC, Sun Shihong, told Sixth Tone that Feng had led a national project to build a functioning model of the seismograph described by the ancient scholar, Zhang. “He hopes the restored seismograph will be able to detect earthquakes, but that goal hasn’t been achieved yet,” Sun explained.

Jiang Xiaoyuan, a history of science professor at Shanghai Jiao Tong University, believes people should be cautious before lauding ancient inventions with scant scientific credibility. “There was no information about the inner structure of the seismograph in the ancient texts, which only claimed it could detect earthquakes,” Jiang said in an interview with online news platform Pear Video.

As another example, Jiang cited a magnetic compass believed to be invented in China during the Warring States period from 475 to 221 B.C. As in the case of Zhang’s seismograph, a physical model was never recovered; however, the historian Wang created a well-known model shaped like a spoon laid over a lodestone. Jiang also questions the authenticity of this model — which was featured during the opening ceremony of the Beijing Olympics as one of China’s “four great inventions.”

“I’d suggest not mentioning these two items in history textbooks,” Jiang said, referring to the spoon compass and the urn seismograph.

Not all netizens seem to share Jiang’s passion for scientific accuracy though. “I disagree. The items are just symbols of Chinese culture — it doesn’t matter whether they’re scientific or not,” commented one user under the video interview. Even Sun, the CENC researcher, believes Zhang’s invention should remain in school textbooks. “As long as the story serves an educational purpose, there’s no need for such abrupt action,” he said.

The new history textbook presents Zhang as the inventor of the world’s first seismograph, and notes that any original models were destroyed. Rather than include an image of Wang’s artistic interpretation, the text now encourages students to search online and offline for other models that have been designed based on the information in their books.

“Such an assignment aims to enhance students’ knowledge of Zhang Heng and the seismograph, and of the wisdom of ancient Chinese people,” People’s Education Press said in its statement on Wednesday. “In this way, national pride will be elevated.”

Editor: David Paulk.

(Header image: Children touch a model of a seismograph at a museum in Yantai, Shandong province, May 11, 2016. Sun Wentan/IC)