487 
the parallax of a Lyra. 
The appearance of parallax which I had found in observa- 
tions of several stars in the same part of the Heavens, also 
might be thought to afford considerable probability that the 
explanation by parallax was not the true explanation. 
The argument furnished by solar nutation, seems to pro- 
duce such additional weight, that, at this time, I consider the 
evidence in favour of parallax greater than ever. 
Mr. Pond, in the concluding paragraph of his Paper, has 
stated, in very strong terms, his opinion of the comparative 
merits of the two instruments ; but I have little doubt that 
opinion will be found quite incorrect, with a reference to this 
point. 
1. In Table III. will be found the differences between the 
microscope A and each of the microscopes of the Greenwich 
circle for every other observation of a Lyrae made during 
seven months. In that time no cause is mentioned in the 
observations for any derangement having taken place. The 
telescope remained in the same position on the circle. In 
the Table IV. will be found the differences between the bot- 
tom microscope and each of the side microscopes of the 
Dublin circle for an equal period. Nothing can be more re- 
markable than the comparative steadiness of the Dublin, con- 
trasted with that of the Greenwich instrument. 
2. The discordances in the Polar distances of the stars 
determined by the Greenwich instrument at different times, 
have long excited notice, and lately Mr. Pond has considered 
these discordances as really existing in the stars, and not 
arising from the observations or the instrument. The con- 
trary has, I think, been sufficiently shown in a preceding 
