6 
larger escaped his notice,) speaks of it as “vix aut ne vix quidem 
sensibilis.” 
The existence of a visible parallax in N. P.D. in certain stars, 
in one at least greater than the solar nutation, that has so long been 
adopted by astronomers, will be considered to add to the troublesome 
corrections already used in finding the mean place of a star. It is 
true, that, with respect to polar distances, it is probable this correction 
may be sensible only in a few stars; but it may be quite otherwise 
as to the right ascensions of stars near the ecliptic. Then, unless it 
be attended to in deducing the catalogue of right ascensions, con- 
siderable inaccuracy will take place. May not this have been the 
source whence the differences have arisen in the recent determi- 
nations of right ascension, deduced from observations made with 
the best instruments ? 
Should it be necessary to consider the constant of aberration as 
unknown, there will be required, for settling the relative places in 
right ascension of two stars only, six unknown quantities (e, , p, for 
each star). Therefore it would require labour almost interminable 
to deduce an ewact catalogue in right ascension of the 36 stars. 
It may be said, that this exactness would be useless. If so, it 
must be admitted, that the right ascensions will be less exact than 
the polar distances. 
The inconveniences that belong to the use of the transit instru- 
ment will also belong to the mural circle, unless means be used for 
referring the observations to the zenith point. This would probably 
deprive the results of several advantages intended by the adoption 
of mural circles. Hence a question of much importance arises, 
Will not the continuation of the construction of mural circles tend 
to impede the progress of our enquiries relative to the fixed stars ? 
Doubtless weighty arguments may be adduced for the constant 
