430 Memoir on the Diminution of the 



in the solsliccs at Loyang, attributed to Tcheou-Kong, arc 

 first «ct down ; after which rules are given to add to, or sub- 

 tract from, the length of these shadows, according as the 

 places are further north or south than Loyang, What I 

 here mention is clearly explained in some of the said works? 

 but in others, the editors have not been careful to give the 

 rules for the increase or decrease of the shadows observed 

 by Tcheou-Kong, for application to places iurther north or 

 south ; whence it arises that in calendars for Nanking or 

 Ilin-tcheou, or other towns, the shadows are ^given for 

 Loyang only." 



From the foregoing, it appears to me that no doubt can 

 be entertained of the quoted observation not wholly belong- 

 ing to Tcheou-Kong. The learned Freret has calculated this 

 important observation in the third part of his excellent Dis- 

 sertation on the Certainty and Antiquity of the Chinese 

 Chronology. This is what he says: 



" The most ancient observation of the solstices that is 

 known with certainty is prince Tcheou-Kong's, brother to 

 Vou-vang the founder of the dynasty Tcheou. Tcheou- 

 -Kong was regent of the empire from the year 1104 to the 

 year 1098. The observation was made in one of these six 

 years. The precise date of the observation for the time of 

 the cycle and moon is not marked, but the place of ob- 

 servation and length of shadows are known. This detail is 

 related in the Tcheou-li, which is a part of the Li-ki or 

 Book. of Kites. 



"A gnomon was made use of, of eight feet Chinese: at the 

 summer solstice the shadow was one foot five-tenths, and 

 in the winter it was 13 feet ; which gives for the obliquity 

 of the ecliptic 23° 54' 14"; the same quantity nearly as was 

 supposed by the ancient Greek astronomers Pytheas, Era- 

 tosthenes, Hipparchus, and Ptolomy. 



" The altitude of the pole at Loyang, (place of the obser- 

 vation) as determined by the altitude of the sun above the 

 horizon and by the resulting obliquity of the ecliptic, is 

 found 34° 4/' 33". Regis and Mailla, by an observation 

 made with accurate instruments, have found it 34° 46' 15". 

 By the obliquity of 23,29 as supposed by our modern astro- 

 nomers, Loyang would be placed at 34° 3-/, differing only 

 15' 13''; which gives room to presume that the obliquity of 

 the ecliptic must have changed. 



" The observation of Tcheou-Kong was made at a time 

 anterior to Solomon's reign, and about the war of Troy. Its 

 exactness proves that observations must have been made in 

 China several centuries back." 



Frerct's 



