Obliquity of the EcUplk. 429 



brother of Vou-vang, in the town of Loyang. According 

 o tradition, a gnomon of eight feet cast at noon a shadow 

 one foot five inches long at the summer solstice. This 

 shadow is mentioned in the ancient hook of Tcheou-li, and 

 in other books, and the authors of the Han consider the 

 observation as incontestable. 



" Loyang is the town of Hon-an-fou in Hon-an. Ac- 

 cording to Father Regis's observation, this town is placed at 

 the latitude of 3<T i$ 15". Father Demaille observed, to- 

 gether with Father Regis, as well at Cai-fong-ion as at 

 Hang-tcheou. 



" A shadow of one foot five inches from a gnomon eight 

 feet long, gives a latitude of near 34° 22', supposing the 

 declination of the ecliptic 23° 29/. Tcheou-Kong governed 

 the empire for his nephew in the year 1 100 before Christ; 

 and it was he' that caused the imperial palace to be built at 

 Loyang, which was a second court of Teheou's empire. 

 Therefore, if we were to admit a declination of v 2Q J 55' at 

 the time of the observation, the latitude would be 34* 

 48' 51"; which is remarkable. 



6i It was again a tradition, that in fhe winter solstice 

 Tcheou-Kong observed with the same gnomon a shadow 

 of 13 feet. This tradition is not so certain as the. former. 

 This shadow would <rivc a true altitude for the sun's centre 

 of 3 1° 18' 42". The summer shadow gives 79° l f 1 1"; — dif- 

 ference 47° 48' 49"; half of which, 23° 54' 24" 80*', would 

 be the ecliptic's obliquity; which is worthy of remark. If 

 the calculation of the ) uitude was made from the shadow 

 at the winter solstice, supposing the declination 23° 2i/, 

 it would give a much more northerly latitude than what 

 the altitude in the summer solstice gives." 



In vol. ii. p. 21, of his History of Chinese Astronomv, 

 published by Father Sauehet, Father Gaubil attributes the 

 same observation to the authors of the Astronomv of Sfefen 

 in the said town of Loyang. But in the manuscript I have 

 just quoted, he relates what follows, [Conn, des Terns JS09, 

 p. 394.) 



The authors of Sfefcn's Treatise of Astronomv have, no- 

 ticed for Loyang at the two solstices, the shadows observed 

 by Tcheou-Kong, and recorded in the first observation. 

 These authors have given shadows for the other days of the 

 year in the equinoxes. These 'shadows are so faulty that 

 no dependance can be placed on the observations. The 

 authors no doubt considered Tcheou-Kong's observation 

 as unreformable. 



" In several treatises of Chinese astronomy, the shadows- 



in 



