parallax of certain fixed stars. 277 
during that time fewer than usual. However, I have been 
able to obtain some results that I shall notice farther on, 
which appear to coincide with my former ones as to u aquilas, 
in a remarkable manner ; and it is to this star that we are, I 
think, to look for the final decision of the question. As to « 
lyrae and arcturus, my results have not been so uniform as I 
had expected from my former observations ; but as to a 
cygni, my recent observations are consistent with my former 
ones, in exhibiting the same discordance between the summer 
and winter observations as before, which appeared to me to 
point out a parallax for that star, but less than for any of the 
other three stars. The results of the observations of Mr. 
Pond, by the fixed telescope, as given in the last volume of 
the Transactions, appear, at first sight, very decisive against 
the existence of any visible parallax in a cygni ; but in con- 
sidering these observations, a difficulty suggests itself, which 
if founded, will render the result deduced from « cygni and 
(3 aurigce quite inconclusive. This, and some other points 
relative to the fixed telescopes, will be noticed farther on. 
If it shall appear that I have been deceived by a constant 
source of error in my instrument as to these stars, it will' be 
of much importance to investigate that source ; and although 
at present I can form no conjecture as to any cause, yet, 
when it shall be found actually to exist, it will be incumbent 
on me to endeavour most strenuously to investigate the 
cause ; and in so doing, I conceive I shall render a most 
acceptable service to astronomers. It will be shown, whether 
it be a cause that will be likely to affect other instruments. 
It appears at present, from the results of Mr. Pond, that the 
