The Han dynasty (206 BCE–220 CE) is known its long reign and its achievements, which included the development of the civil service and government structure; scientific advancements such as the invention of paper, use of water clocks and sundials to measure time, and development of a seismograph; the Yuefu, which compiled descriptions of music; the Shiji, a history written by Sima Qian; the fu, a poetic form; and lacquerwork and woven silk.