146 
EASTMAN. 
noctial Colure, to argue from him concerning the change of 
the Obliquity of the Ecliptick, but Ptolomy gives him 33' 
more North Latitude than he now has; and that greater 
Latitude is likewise confirmed by the declinations delivered 
by the abovesaid observers. So then all these three stars are 
found to be above half a degree more Southerly at this time 
than the Antients reckoned them. When on the contrary 
at the same time the bright shoulder of Orion has in Ptol¬ 
omy almost a degree more Southerly Latitude than at 
present. What shall we say then? It is scarce credible 
that the Antients should be deceived in so plain a matter, 
three Observers confirming each other. Again these stars 
being the most conspicuous in Heaven are in all probability 
the nearest to the Earth, and if they have any particular 
Motion of their own, it is most likely to be perceived in 
them, which in so long a time as 1800 Years may shew itself 
by the alteration of their places, though it be utterly imper¬ 
ceptible in the space of a single'century of Years.” 
From the date of this paper begins a new and important 
epoch in the history of Astronomy. 
Foremost among the reasons leading to the choice of a 
subject for this meeting, was the conviction that the history 
of this branch of astronomy in all the phases of its evolu¬ 
tion illustrates the conflict in every department of science 
between the Philosophy which rests alone on assumption, 
and that which is founded on observation. In this view of 
the subject, each member of the Philosophical Society lias, 
an interest, and therefore I bespeak your attention, while I 
briefly trace the evolution of those theories which have been 
adopted to explain the peculiar motions of the stars among 
themselves, and to account for the motion of the Sun in a 
certain direction among the stars. The first phenomenon is. 
known as “ Proper Motion of the Stars,” and the second, as- 
“ Motion of the Solar System in Space.” As the sun itself is 
only a rather insignificant star, there seems to be no real ne¬ 
cessity for two names for the same phenomenon, but custom 
is sometimes more powerful than reason. 
