THE PLANETS. 455 



have come down to us, with accurate numerical data, rcacn 

 back to the year 1 104 before Christ, and testify to the extreme 

 antiquity of Chinese civilization. The literary remains are 

 scarcely a century more recent, and a regulated calculation of 

 time extends (according to Edward Biot) as far back as 2700 

 years before Christ. 40 Under the reign of Tscheu-Kung, the 

 brother of Wu-Wang, the meridian shadows were measured 

 in two solstices, upon an eight-foot gnomon, in the town of 

 Layang, south of the Yellow River (the town is now called 

 Ho-nan-fu and is in the province of Ho-nan), in a latitude of 

 of 34 46'. 41 These measurements gave the obliquity of the 

 ecliptic as 23 54'; that is, 27' greater than it was in 1850. 

 The observations of Pytheas and Eratosthenes at Marseilles 

 and Alexandria are six and seven centuries later. We pos- 

 sess the results of four observations of the obliquity of the 

 ecliptic previous to our era, and seven subsequent, up to 

 Ulusjh Beg's observations at the observatory of Snmarcand. 

 The theory of Laplace corresponds sometimes in plus, some- 

 times in minus, in an admirable manner with the observations 

 made during a period of nearly 3000 years. The knowledge 

 transmitted to us of Tscheu-Kung's measurement of the 

 shadow-length is so much the more fortunate as the manu- 

 script which mentions it escaped, from some unknown cause, 

 the fanatical destruction of books commanded by the Emperor 

 Schi-hoang-ti of the Tsin dynasty, in the year 246 before 

 Christ. Since the commencement ol the fourth Egyptian 

 dynasty with the Kings Chufu, Schafra, and Menkera, the 

 builders of the Pyramids, falls, according to Lepsius, twenty- 

 three centuries before the solstitial observation at Layang, 



40 Cosmos, vol. ii. p. 475, 476, and note. 



41 Laplace, Expos, du Systeme du Monde, 5th ed. p. 303, 

 345, 403, 406, and 408 ; the same in the Connaissance des 

 Temps pour 1811, p. 386; Biot, Traite EUm. d'Astron. 

 Physique, torn. i. p. 61 ; torn. iv. p. 90-99, and 614-623. 



