History of Astronomy for the Year 1805. 339 
place there gives some new results wpon the masses of the 
planets; and he has latterly confirmed them by the calcula- 
tion of an old Chinese observation on the obliquity of the 
ecliptic, made 1100 years before the vulgar cera, which gives 
23° 54’, while he finds 52” by his theory, (tom. ii. 1. vie- 
ch. 16) ; another observation, 100 years before our era, gives 
23° 45’, while it is 44’ by the theory: this confirms the mass 
of Venus made use of by M. de Laplace, and the diminu- 
tion of the obliquity of the ecliptic of 52” per annum, al- 
though several observations have seemed to give only 36”. 
We have received a book (196 pages in 8vo.) containing 
the exposition of the operations made in Lapland for the des 
termination of an arc of the meridian in 1802, by Messrs. 
Osverbom, Svanberg, Holmquist, and Palander. They made 
use of the new decimal measures ; a procedure which I think 
the duty of all those who interest themselves in the progress 
of truth. 
The result {p. 187) is, that the degree, of which the mid- 
dle passes at 66° 20’, is 111477°4 metres, or 57196°2 toises; 
but to make this reduction they have supposed the metre to 
be 443°2959 lines, as the commissioners of weights and 
measures have made it in France; and for that purpose they 
took the metre at the freezing point, and the toise at the 
13° of the thermometer of 80°. It seems to me most na- 
tural to take them both at the mean temperature, which is 
4°. By amean between the observations of several years, 
it is the zero of my new thermometer: for this we must 
subtract 0-064 lines from the metre, and add 0°046 lines ta 
the toise, according to the experiments made by M. Lavoi- 
sier, and in which IJ took a part in 1782; and we may make 
this proportion ; 863°954 : 448°360 :: 854 lines are to the 
metre; and thus it is found to be 443°435 lines in place of 
296. Itis to this yalue that [ shall change all the. mea- 
sures in my astronomy, as I announced to the Institute on 
the 28th of October. Thereby I find that we must subtract 
154 metres from the number above given, and that the de- 
gree is 57200. 
The degree of 1736 having been measured at 15°, there 
must be added to it three toises; that of 1802, having been 
measured 
