SOLAR AND STELLAR PROPER MOTIONS. 
145 
at Greenwich, read a paper before the Royal Society enti¬ 
tled “ Considerations on the Change of the Latitudes of some 
of the principal fixt Stars.’’ He had been engaged upon an 
investigation of the precession of the equinoxes, and by com¬ 
paring the declinations of the stars contained in Ptolemy’s 
Almagest with the declinations of the same stars obtained 
nearly two thousand years later, he had reached a point 
whence he was enabled, on well considered evidence, to sug¬ 
gest the probability of motions that were destined to over¬ 
throw the well worn theories of the immobility of the solar 
system. 
On account of the historical importance of this paper, I 
venture to give the following leading points in the author’s 
own language. 
“ But while I was upon this Enquiry, I was surprized to 
find the Latitudes of three of the principal Stars in Heaven 
directly to contradict the supposed greater obliquity of the 
Ecliptick, which seems confirmed by the Latitudes of most 
of the rest; they being set down in the old Catalogue as if 
the Plain of the Earth’s Orb had changed its Situation, 
among the fixt Stars about 20' since the time of Hipparchus. 
Particularly all the Stars in Gemini are put down, those to 
the Northward of the Ecliptick, with so much less Latitude 
than we find, and those to the Southward with so much 
more Southerly Latitude. Yet the three Stars Palilicium 
or the Bull’s Eye, Sirius and Arcturus do contradict this 
rule directly: for by it, Palilicium being in the days of 
Hipparchus in about 10 gr. of Taurus ought to be about 15 
Min. more Southerly than at present, and Sirius being then 
in about 15 of Gemini ought to be 20 Min. more Southerly 
than now; yet, & contra, Ptolomy places the first 20 Min. 
and the other 22 more Northerly in Latitude than we now 
find them. Nor are these errors of Transcription, but are 
proved to be right by the declinations of them set down by 
Ptolomy, as observed by Timocharis, Hipparchus and him¬ 
self, which shew that those Latitudes are the same as those 
authors intended. As to Arcturus, he is too near the Equi- 
