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 by the most cautious Chinese historian Sze-mâ-ch‘ien, place Yin's expedition in the reign of Chung K‘ang. The Annals of the Bamboo Books, which preserve a system of chronology known to and sometimes used by Tso and Sze-mâ-ch‘ien, give an exact date, equivalent to our B.C. 1948, October 28. Unfortunately there was no eclipse that day, not even a new moon. Sze-mâ-ch‘ien refused to trace Chinese chronology further back than B.C. 841. Before that date he has no scheme of chronology beyond the bare names of emperors with their relation to each other. Tracing back the line, we may infer that Chung K‘ang must have reigned within a century or two one side or other of B.C. 2000.

The Chinese astronomers of the T‘ang dynasty A.D. 618–906) endeavoured to fix the date of the eclipse by computation. They were divided between B.C. 2155 and B.C. 2128, and the received Chinese chronology, which is the work of Shao K’ang-chieh, who lived in the eleventh century of our era, is based on the two assumptions that the first of these dates is correct, and that the eclipse fell in the fifth year of Chung K‘ang. But, as Largeteau showed in 1840, the eclipse of B.C. 2155 was not visible in China, a discovery which has given rise to the well-known rhyme:

The chief difficulty in identifying the eclipse lies in the two uncertainties already mentioned, whether the first month of summer or last month of autumn is the