434 Diminution of the Obliquity of the Ecliptic* 



in the quoted manuscript; in which is read as follows :(Comr, 

 des Terns, I8O9.) 



" Lieou-hiano-, father of Lieou-hia, wrote upwards of 50 

 years before Chiist. This author says that an eight -feet 

 gnomon gave the noon shadow in the winter solstice 13 

 feet one inch four fen, in the summer's it was one foot 

 five inches four fen. Litchun-foung, an astronomer of 

 the dynasty of the Tangs, complains that these shades were 

 improperly applied to Siganfou. Lieou-hiang mentions 

 neither the place nor the time of these observations." 



The shade at the summer solstice is not exactly the 

 same as that published in the quoted History of Chinese 

 Astronomy ; but I think that this last ought to be preferred, 

 the shadow given in the MS. giving an evidently too con- 

 siderable obliquity of ecliptic. It is very likely that in the 

 manuscript Father Gaubil may have written, in a mistake, 

 instead of eight fen the same number that he wrote for the 

 winter solstice. Adopting therefore, lft, 14 and 13ft, 58 

 for the lengths of the shadows at the summer and 

 winter solstices, and allowing for the refraction and the 

 sun's parallax, I find 31° 2' 23" and 78° 33' 4l" for the 

 altitudes of the sun's centre, resulting from these observa- 

 tions. Half of their difference gives 23° 45' 39" for the 

 ecliptic's obliquity. If we add it to the complement of 78* 

 33' 41", we shall have for the altitude of the pole 35° 11' 

 58", an altitude very different from that of Siganfou, which 

 the Jesuits have found 34° 16' 45''. Litchun-foung was 

 therefore right to complain that these noon shadows had 

 been improperly referred to Siganfou. 



To compare my formula with this observation, I suppose 

 that t = — 1850, and then it gives for the obliquity of the 

 ecliptic 23° 43' 59" ,4, and by adding 5', as we have done 

 for the preceding observation, we shall have 23° 44' 4'', 4, 

 which only differs l' 34",6 from the result of this second 

 observation. These two observations are the only ones 

 before the commencement of our sera, that Father Gaubil 

 has made us acquainted with; and it is to be supposed that 

 this learned missionary could not discover others : the de- 

 struction of books by fire, which took place 213 vears pre- 

 vious to the Christian aera, having caused the loss of the 

 •greatest number of preceding observations. 



[To be continued.] 



LXXVHI. Re- 



