declination of some of the fixed stars. 45 
of these deviations depends on error of observation caused by 
some defect in the instruments employed : this investigation 
becomes the more necessary, as it does not appear that Dr. 
Brinkley, with his instrument at Dublin, has met with similar 
discordances. Admitting the accuracy of the observations of 
Bradley to form the ground-work of this enquiry, there are 
then two distinct hypotheses, that may be formed by those, 
who are inclined to maintain, that the proper motions of the 
stars are uniform ; and that the discordances in question have 
their source, not in any astronomical cause, but in some erro- 
neous system of observation. Of the observations from which 
the catalogues of 1813 and of the present year have been 
computed, we may suppose the one or the other to be erro- 
neous. Let us consider the consequences of each hypothesis. 
Let us first suppose the error to be in the observations 
of 1813 . Then the observations of 1756 and 1822 being 
supposed perfect, a catalogue for the year 1813 may be com- 
puted by interpolation ; such a catalogue is annexed, and 
this, (assumed to be correct,) compared with the observed 
catalogue of 1813 , will show the errors of observations at 
that period. On this assumption the Greenwich circle must, 
in 1813 , have been in a very defective state; and admitting 
the instrument to be now perfect, this can be only attribu- 
ted to the insufficiency of the braces which then connected 
the telescope to the circle ; for this is the onlv difference 
between the instrument in its former and in its present 
state. The natural tendency of any such defect would be, I 
think, continually to increase, and to give results every year 
more and more distant from the truth : but this is contrary 
to the known history of the Greenwich observations, which I 
