[ 126 3 
X. Correction of an error in a Paper published in the Philoso- 
phical Transactions , entitled, “ On the Parallax of the fixed 
Stars By J. F. W. Herschel, Esq. F. R . S'. 
Read February 22, 1827. 
In my Paper on the parallax of the fixed stars, published in 
the Philosophical Transactions for 1826, by inadvertence the 
letter / was written for X, in the formula for computing the 
most advantageous times of year for observations on the pa- 
rallax of a double star. The mistake was detected, and 
rectified in an erratum annexed to the 4th Part of the Trans- 
actions for that year, but not till the table computed by the 
erroneous formula was printed off, and too late to cancel the 
sheet. The errors produced fall wholly on the 5th column 
of the table in pages 277, 278, of the volume for that year, 
headed, “ Times of the year most proper for observation 
which column I have therefore had recomputed, and which is 
here subjoined. I am happy to be able to add, that except in 
a few instances, the differences are not so considerable as to 
render useless any observations which may have been made 
on the plan proposed, as in the great majority of instances 
the correct dates do not differ by more than a week from the 
erroneous ones ; and about the times proper for observation, 
a week or a fortnight one way or the other is of no essential 
moment. 
