6a6 



PHILOSOPHICAL TRANSACTIONS. 



[anno 1790. 



Venus has been supposed in the tables of Cassini, Halley, and De la Lande, = 

 3° 13' 20", and the error of the tables + 18".6. 



3. The heliocentric longitude and motion of the nodes of Mars. 

 In a Paper printed in the Memoirs of the Royal Academy of Sciences at Stock- 

 holm, is determined the heliocentric longitude of Mars's ascending node = V 

 17° 54' 24''.2, in the year 1783, December 7, 10^ 23™ 39", mean time at 

 Copenhagen: the error of Cassini's tables — 10' 35'', of Halley*s tables — 23' 27", 

 of De la Lande's tables — 4' 37''. The annual motion of Mars's node may be 

 found by comparing the following observations of the longitude of the node. In 

 the column a the numbers are going upwards from the observation 1783 ; in the 

 column B the numbers are going downwards from the observation 1595. 



Astronomers' 

 Names. 



Time of observation, 



Tycho Brahe . . 



Cassini 



Cassini 



De la Caille . . . 

 De la Caille . . . 

 Maskelyne .... 

 Bugge 



1595, Oct. 28 



1700, May 6 



1721, Nov. 13 



1747, May 14 



1753, Nov. 4 



1778, April 17 



1783, Dec. 7 



The mean of the 2 series a and b will give the most probable annual motion of 

 Mars's node IS". 2, In Cassini's tables the annual motion is 34'', in Halley's 38", 

 and in De la Lande's 40". 



4. The inclination of the orbit of the planet Mars. 



Error of the tables of 

 M. de la Lande, 



The geocentric longitudes of Mars are corrected for aberration and nutation, 

 and compared with De la Lande's newest tables, which after the last improve- 



