50 



argument is not quite so strong with respect to a Cygni. The 

 computed N. P. distances are deduced from Bradley's N. P. dis- 

 tances in 1755. 



The above agreement of the computed and observed places affords 

 matter for considerations not immediately connected with our pre- 

 sent enquiry. The circumstances relative to the exactness of the 

 instruments and observations that have produced such coincidences 

 are worth being investigated, and may perhaps be the subject of a 

 future communication. 



Assuming Rigel, a Orionis, and Sirius without proper motion, 

 we may deduce the motion of the ecliptic on the equator. 



Let da represent the motion of the ecliptic on the equator be- 

 tween 1755 and 1821. Then with the right ascensions and north 

 polar distances, and obliquity of the ecliptic in 1755, =23° 28' 15^2, 

 we obtain as follows : 



