THE 

 LONDON, EDINBURGH and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FOURTH SERIES.] 



JANUARY 1862. 



I. On Chinese Astronomical Epochs, 

 By Archdeacon J. H. Pratt, M.A. 



To the Editors of the Philosophical Magazine and Journal. 

 Gentlemen, 



IN the absence of authentic history, astronomy sometimes lends 

 valuable aid in enabling us to fix dates by independent means, 

 if certain facts have been handed down to us regarding the posi- 

 tions of the heavenly bodies. There are two eras in Chinese 

 history which it has been attempted to fix in this manner : — one, 

 the reign of the emperor Tcheou-kong, said to have lived about 

 1100 B.C.; the other, that of the emperor Yao, many centuries 

 earlier, about 2357 B.C. The traditions regarding these persons 

 are vague and altogether uncertain. My object in the present 

 communication is to show what degree of reliance can be placed 

 on the astronomical determinations. However perfect the methods 

 may be which modern science puts into our hands, the results to 

 which they lead us can be of no value if the data are not suffi- 

 cient and also trustworthy. 



On the determination of the Era 1100 B.C. 



2. M. Gaubil, a Jesuit missionary at Pekin, sent to Paris in 

 1734 a MS. of Chinese astronomical observations, which Laplace 

 published in the Connaissance des Terns for 1809. The oldest 

 observations which Laplace considered to be of any value for 

 astronomical purposes (as he there tells us) are two observations 

 of the length of shadow cast by a gnomon at the summer and 

 winter solstices in the time of Tcheou-kong at a place Tching- 

 tcheou, called also Loyang and Hon-an-fou. The latitude of this 

 place was observed by the missionaries in 1712 three times, and 

 found to be 34° 52' 8" by one observation, 34° 46' 15" by the 

 second, and 34° 43' 15" by the third, the last being considered 

 the best. The vertical style or gnomon was 8 feet (pieds) high, 



Phil. Mag. S. 4. Vol. 23. No. 151. Jan. 1862. B 



