364 Astronomical and Nautical Collections, 



(d + 2/0 k). 



d + 6k 



iv. Remarks on Professor Struve's Observations to determine the 

 Parallax of the fixed Stars. By J. Pond, Esq., Astr. Royal. 



Of the various attempts to discover the parallax of the fixed 

 stars, the observations of Professor Struve must be regarded as 

 among the best and most judicious. [Obs. Vol. II. III.] 



His object is, by means of an excellent transit instrument 

 furnished with seven wires, to determine the sum of the parallaxes 

 of several fixed stars, differing nearly 12 hours in right ascension 

 from each other. 



The results which he obtains seem to verify a remark which I 

 have often had occasion to make ; that in proportion as any im- 

 provement takes place either in our instruments or our processes 

 the resulting parallax becomes proportionally less. 



Of fourteen sets of opposite stars thus compared, Mr. Struve 

 finds seven, which give the parallax negative ; this circumstance 

 alone should suggest great caution in attributing to the effects of 

 parallax the small positive quantities that are derived from the 

 remaining seven. Mr. Struve however is inclined to assign 0".16 

 of space as the parallax of £ Ursae Minoris, and 0".45 for the 

 sum of the parallaxes of a, Cygni, and i Ursae Majoris. His 

 learned coadjutor, M. Walbeck, who, it appears, has undertaken 

 the calculations, is disposed to attribute the greatest portion of 

 this parallax to the smaller star ; a circumstance so improbable 

 requires very strong evidence for its support. 



But whatever reasonable doubt we may entertain as to* any 

 one given result relating to such extremely minute quantities, yet 

 the mean of the whole must be admitted to deserve very great 

 confidence ; and it is to this view of the subject (omitted by the 

 learned author,) that I wish to direct the attention of Astronomers. 



* It should be remembered, that in a series of observations, it generally 

 happens that some results will be erroueous by a greater (juantity than the 

 mean probable error. 



