COMMENTATIO ASTRONOMICA. 



203 



« The first column shews Ihe year and day of Ihe observations ; Ihe secönd the zenith 

 «dislances of Sirius at the Cape of Good Hope , as delivered in Abbe de la Caille's 

 « recital ; the third contains the computed values of the parallax at different times, ta- 

 « king that of the maximum 9" , the fourlh column gives observations reduced to the 

 « mean , by applying the parallax computed in the third column to the observations in 

 « the second; which quantities ought all to agree together, if the observations were lia- 

 « ble to no error, and the parallax was rigthly assumed: but , taking a mean of them 

 « all , the last column shews how much each of them differs from that mean , which , 

 « in general , is very small , and scarce exceed 2" , except in two observations , ia one 

 « of which it amounts to 3", and the olher to 4": but these differ as much from the 

 « mean of the sis other observations made at the same season of the year. Thus , assu- 

 « ming a parallax , the observations will be found to agree as well with that supposi- 

 « tion , as they do with one another. But if th« observations are considered in themsel- 

 « ves , without any allowance for parallax , they will differ sensibly from one another : 



C c 2 « nor 



