12C COSMOS. 



recent, and a regulated calculation of time extends (accord- 

 ing to Edward Biot) as far back as 2700 years before Christ.* 

 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 34° 46'. f 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 possess the results of four 

 observations of the obliquity of the ecliptic previous to our era, 

 and seven subsequent, up to Ulugh Beg's observations at the 

 observatory of Samarcand. The theory of Laplace corresponds 

 sometimes in plus, sometimes in minus, in an admirable man- 

 ner with the observations made during a period of nearly 3000 

 years. The knowledge transmitted to us of Tscheu-Kung's 

 measurement cf the shadow-length is so much the more for- 

 tunate, as the manuscript which mentions it escaped, from 

 some unknown cause, the fanatical destruction of books com- 

 manded by the Emperor Schi-hoang-ti of the Tsin dynasty, in 

 the year 246 before Christ. Since the commencement of 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 observa- 

 tion at Layang, it is indeed very probable, from the high de- 

 gree of civilization of the Egyptian people and their early 

 regulation of a calendar, that even at that time the length 

 of shadows had been measured in the valley of the Nile ; but 

 no knowledge of this has come down to us. Even the Peru- 

 vians, although less advanced in the perfection of calendars 

 and intercalations than the Muyscas (mountain inhabitants 

 of New Granada) and the Mexicans were, possessed gno- 

 mons, surrounded by a circle marked upon a very level sur- 

 face. They stood in several parts of the empire, as well as 

 in the great temple of the Sun at Cuzco ; the gnomon at 

 Q/Uito, situated almost under the equator, was held in great- 

 er veneration than the others, and crowned with flowers upon 

 the equinoctial feasts. $ 



* Cosmos, vol. ii., p. 114, 115, and notes. 



t Laplace, Expos, du Systeme du Monde, 5th ed., p. 303, 345, 403, 

 406, and 408 ; the same in the Connaissance des Temps for 1811, p. 386 

 Biot, Traits Elem. d'Astron. Physique, torn, i., p. 61 ; torn, iv., p. 90-99 

 and 614-623. 



X Garcilaso, Comment. Reales, part i. lib. ii., cap. 22-25 ; Prescott 



