66 
Dr. Brinkley on the 
The above remarks, relative to the mean difference of 
Catalogues, have been adduced only because I hope they will 
be found to contain some useful illustration on this subject. 
The proofs I shall now bring of the non-existence of a 
southern motion, are derived from comparing, in years re- 
mote from each other, the places of particular stars, supposed 
by Mr. Pond to have a considerable southern motion, with 
others supposed to have none, or only a very small southern 
motion. Whatever doubt may arise when we reason on such 
small quantities as the mean difference, none can occur with 
respect to several particular stars that have been supposed 
to have a great southern motion. 
The conclusion that follows is, that there is no southern 
motion similar to what Mr. Pond has deduced. There may 
be certain stars of which the proper motions are not uniform. 
In some stars these may have a tendency to diminish, and in 
others to increase, but nothing of this kind is as yet certainly 
known. Perhaps, hereafter, it may be confirmed that the 
proper motion of Procyon is increasing. 
(I) The stars & Cassiopea? and y Ursa? Majoris, are par- 
ticularly considered by Mr. Pond. According to him, a 
Cassiopeae appears to have a considerable southern motion 
relatively to y Ursa? Majoris. 
It is a somewhat singular circumstance, that Dr. Bradley 
observed, with great care, at Wanstead, in 1727 and 1728, 
the difference of declination between these two stars. It is 
worth while to quote his own words.* 
“ But as it may be of some use to future astronomers to 
“ know what were the mean differences of declination, at a 
given time, between some stars that lie nearly opposite to 
* Phil. Trans. Vol. 45. Old Abridg. Vol. 10, p. 51. 
