42S Metnoir on the 'Diminution of I he 



lions to be made in places westward, eastward, northward, 

 and southward, of Tching-teheou. 



"In the town of Tching-teheou, a gnomon eight feet 

 long gave at noon, at the summer solstice, a shadow of one 

 foot live inches. The declination of the sun being sup- 

 posed 23° 2o/> the observation of Tcheou-Kong gives the 

 north latitude 34° 22' 3". 'Hie centre of the town Hon-an- 

 fou has been observed at a latitude of 34° 43' 15", with an 

 instrument made by Chapontot, by several altitudes of the 

 ?un : — difference between the missionaries' observations and 

 Tcheou-Kong, 21' 10', of which quantity Hon-an-fou 

 would appear to be more to the northward than given by 

 Tcheou-Kong's observation. Although the exact situation 

 of the town of Tching-teheou cannot be ascertained, it 

 appears that the difference from Hon-an-fou cannot give 

 a di (Terence of 21' 10". A want of accuracy in the observa- 

 tions, particularly in the gnomon, might produce a part of 

 this difference. 



" The missionaries supposed a declination in the ecliptic 

 of 23° 20/ : ihey applied refraction, parallaxes, and diame- 

 ter of the sun, agreeably to de la Hire's new Tables, and 

 thought they were sure of the adjustment of the instrument. 

 The difference may also arise from some change in the obli- 

 quity of the ecliptic." 



I shall in the first place observe, that the Chinese divide 

 the. foot into ten inches, the inch into ten fen, the fen into 

 ten li, the li into ten Jiao, &c: so that thelength of the shadow- 

 is one foot five inches. As to the latitude of 34° 43' 15" of the 

 town of Tching-teheou, the same as has been designed by 

 the names of Loyang and Hon-an-fou, Father Gaubil, in a 

 note of the page just cited from " Edifying Letters," says 

 that that observation was made in June 1712 : that according 

 to one observation this latitude was found 34° 52' 8"; and 

 to a. second, 34° 46' 15"; lastly, that a third gave 34° 43' 

 15/' This last appears to him preferable to the other two. 

 The difference of these results proves the want of exactness 

 in those observations, which, combined with the incertitude 

 < i the exact place of Tcheou-Kong's observations, would 

 render it highly desirable to. know the length of the shadow 

 in the winter solstice, at the time of that prince. 



This is what I find on this subjeei in the j\IS. cited by 

 Father Gaubil. [Conn, des Terns for I 809, p. 3Q3v) 



" At all times the Chinese have observed the sun's 

 shadow at noon, and at other times; but the most ancient 

 observation we are possessed of is that of Tcheou-Kong, 



brother 



