pierce a surrounding paper cylinder, have been described." Hong-sen Yan states that modern replicas of Zhang's device have failed to reach the level of accuracy and sensitivity described in Chinese historical records. Wang Zhenduo presented two different models of the seismoscope based on the ancient descriptions of Zhang's device. In his 1936 reconstruction, the central pillar (du zhu) of the device was a suspended pendulum acting as a movement sensor, while the central pillar of his second model in 1963 was an inverted pendulum. According to Needham, while working in the Seismological Observatory of Tokyo University in 1939, Akitsune Imamura and Hagiwara made a reconstruction of Zhang's device. While it was John Milne and Wang Zhenduo who argued early on that Zhang's "central pillar" was a suspended pendulum, Imamura was the first to propose an inverted model. He argued that transverse shock would have rendered Wang's immobilization mechanism ineffective, as it would not have prevented further motion that could knock other balls out of their position. On June 13, 2005, modern Chinese seismologists announced that they had successfully created a replica of the instrument. Anthony J. Barbieri-Low, a Professor of Early Chinese History at the University of California, Santa Barbara, names Zhang Heng as one of several high-ranking Eastern-Han officials who engaged in crafts that were traditionally reserved for artisans (gong 工), such as mechanical engineering. Barbieri-Low speculates that Zhang only designed his seismoscope, but did not actually craft the device himself. He asserts that this would most likely have been the job of artisans commissioned by Zhang. He writes: "Zhang Heng was an official of moderately high rank and could not be seen sweating in the foundries with the gong artisans and the government slaves. Most likely, he worked collaboratively with the professional casters and mold makers in the imperial workshops." Cartography The Wei (220–265) and Jin Dynasty (266–420) cartographer and official Pei Xiu (224–271) was the first in China to describe in full the geometric grid reference for maps that allowed for precise measurements using a graduated scale, as well as topographical elevation. However, map-making in China had existed since at least the 4th century BC with the Qin state maps found in Gansu in 1986. Pinpointed accuracy of the winding courses of rivers and familiarity with scaled distance had been known since the Qin and Han Dynasty, respectively, as evidenced by their existing maps, while the use