FAVOURABLE TO THE INVESTIGATION OF PARALLAX. 
337 
with those given by other observers, exhibit changes of such an amount in their angle 
of position as to afford satisfactory evidence of orbital motion. 
This fact being admitted, it is plain that these stars cannot be rendered available 
in the present inquiry ; it was deemed unnecessary therefore to extend to them the 
method of reduction employed in the case of the other stars ; the observations, how- 
ever, are given with the others in their proper place. 
The third and seventh columns of the table contain the arithmetical mean of the 
individual measures, both in position and distance, obtained on the day specified in 
the first column. 
The quantities inserted in the fourth and fifth columns headed “probable error” 
and “ computed weight,” refer to the positions only, and have been computed from 
the formulee 
0-45494 
n[n— 1 ) 
X sum of £^, 
W=p, 
where P= probable error of a single set of measures, 
n= the number of measures, 
£= the individual errors, 
and W= the weight of the result; 
numbers proportional to the computed values of W being inserted in the Table. 
The average probable error of all the sets, 21 1 in number, is 8'‘98, and the average 
weight, 0'0124. 
The quantities inserted in the sixth and eighth columns, headed “ assigned weight,” 
represent the sum of the weights, divided by 10, assigned by the observer to the indi- 
vidual measures of position and distance forming the set, or the arbitrary weights 
of the sets. 
The magnitudes and colours of the stars were noted on each night of observation, 
and are inserted in the ninth and tenth columns ; where one colour only is named, 
it is to be understood as applying to both stars ; and where two are specified, the 
colour of the brighter component, or, in cases of equal brightness, of the star called 
A, is placed first in order. 
The eleventh column contains the initial of the observer’s name. 
The results of each epoch and year are for the sake of distinctness separated by a 
blank space. 
