Rosenberger on Halley's Comet at its last Appearance. 33 



With these elements I calculated, first, the disturbing forces 

 A, B, C; of which the two first act in a direction parallel to 

 the plane of the ecliptic, from the vernal to the autumnal 

 equinox (A), and from the summer to the winter solstice (B), 

 and the last from north to south perpendicular to the eclij)tic 

 (C). I was compelled, by the circumstances of the comet's 

 near approach to Venus, and subsequently to the earth, to 

 calculate in general for intervals of 10 days, but from the 10th 

 of April to the 10th of May, for every 2^ days. The masses 

 of the planets were supposed in this calculation as follows : 



Mercury ^^^^_ -— - 



•' 2025810 



Venus -—g-—f according to Burkhardt. 



^^'' ^6553 



J^P^t^'" WotI ,. „ , ^, 



J j accordmg to Bouvard, Tables 



Saturn > de Jupiter, de Saiurne, et 



, I d' Uranus, 1821, p. II. 



Uranus -^^^J 



The Earth „^^^„, 



357594 



which last value is obtained, if the horizontal parallax of the 

 sun is assumed = 8""5776 according to Encke, instead of 

 8"*74'8 according to Laplace. (Expositio?i du Syst. du Motide, 

 livre ii. chap, iii.) 



[//t're the autlior gives a table of the values of the quantities 

 A, B, C, 'dchence he deduces a table of the variations of each 

 of the elements of the comet for every tenth day from January 

 to January 160, for ■which the reader is referred to the Astrono- 

 misclie Nachrichten.] 



As this table shows the changes which the planetary distur- 

 bances produce in the elements of the comet from noon Ja- 

 nuary 1759, till any given moment of the time during which 

 it remained visible, an exact ephemeris for three periods of 

 its appearance, viz. Irom the 22nd of January to the 5th of 

 February, from the 31st of March to the ICth of April, and 

 from the 30lh of April to the 3rd of June, was calculated with 

 the above-named elements. For this I employed Bessel's Cor- 

 rections of Carlini's Sohir Tables, and considered the influ- 

 ence of the disturbances, by correcting the values of the true 

 anomaly, and of the radius vector belonging to the unchanged 

 elements, on account of the variations of //, e, T, and w, and 



N. S. Vol. 11. No. 61. Jan. 1832. F correcting 



