302 



Motion of the Solar System hi Space. 



[APiRIL 



Notwithstanding the want of agreement of these several columns, 

 on inspecting that containing the " general mean," we find something 

 more nearly approaching to regularity, than should exist, were these 

 numbers the effect of chance -f- or — true proper motion only ; we find, 

 with hut one exception, that all the quantities are affected with the 

 sign 4-> find we find in the neighbourhood of 0 hours, that it arrives at 

 a maximum. Now the only circumstance which offers to account for 

 this determination to the sign 4-> is a wrong assumption of the gene- 

 ral precession in longitude ; for, on reference to figure 3, where P 

 represents the pole, and S. S. S. the circle around which our cata- 

 logue of stars is supposed to be congregated, we find, on dividing this 

 circle into hours III, VI, &c. and drawing the line N. P., that all the 

 stars situated to the left of this line, viz. between XVIII and VI hours, 

 w ill, by a motion of the solar system towards N, have their right 

 ascensions increased,* whereas those situated on the right, in the 

 remaining 12 hours, will be diminished by the like amount; or, in 

 other words, the mea?i of the 24 results in the column " general 

 mea?i,'' is free from the effect of any motion which may exist in the solar 

 system; if then, with reference to the formula for the precession in 

 right ascension, (Precess. A. R. = .46.021" -f 20.043'' sin a tan. 



and the position of the stars constituting each group, we compute 

 the change of precession, due to a change of 1 for instance, 



in the general precession in longitude, vre obtain as follows : 



Error of the column " Mean P. M. in A. i?." corresponding to an 

 error of 1" in the general precession in longitude. 



Right Ascension. Error in Time. Right Ascension. Errorin Time, 



h. m. h. m. s h. m. ^' h. m. s, 



0. 30&XI. 30 -= ,063 XII. 30 — XXIII. 30 .060 



1. 30 — X. 30 = ,066 XIII. 30 — XXII. 30 .058 



II. 30— IX, 30 = ,068 XIV. 30 — XXI. 30 .055 



III. 30 - VIII.30 = ,070 XV. 30 — XX. 30 .053 



IV. 30 — VII. 30 = ,071 XVI. 30 — XIX. 30 .052 



V. 30 — VI. 30 = ,073 XVII.30 — XVIII. 30 .051 



Here we immediately perceive, that applying the corrections due to 

 an alteration of 0,04'' in the general precession in longitude will re- 



* An advance tOAvaids the point N. necessarily increases the angle between it and any- 

 star S. in proportion to the sine of the arc N.S.— 2. e. the star appears to move from S. to 

 S., producing an alteration in the A. R. and in the IS. P. D. 



