COMMENTATIO ASTRON OMICÄ^ 235 



« a Aquilae. The annexed table contains 120 observations of this star; and the follo- 

 « wing remarks will , 1 trust , be thought sufficiently conclusive to establish the point 

 « in question." 



« If a series of 12 results (obtained by 120 observations) be divided into two x»arls> 

 « first, according to the law of parallax, and next alternately, or in a nianner per- 

 « fectiy accidental, then it so happens, that a greater differenee is found in the latter 

 « or accidental mode of division, than in the former. From this it is evident, that the 

 « determination of the quantity of parallax is out of the power of the instniment to de- 

 « termine with this number of observations. The next question is, what are the limils 

 « within which parallax is restricted ? " 



« In examining several series of observations, I find that the result of 60 observations, 

 « reduced to the «quatpr , and taken accidentally , never differs from the more correct 

 « mean derived from 120 by more than 0",01 of time, when reduced to the equator. " 



« If of 12 results taken as above, the 6 least be classed together, and compared with 

 « the six greatest, the error of either elass will not exceed the double of Ihis quanlily, 

 « or 0".02. It is therefore very highly improbable indeed , that an error of this magni- 

 « tude should exist in a result deduced from 60 observations. " 



« Since therefore , the results arranged accoiding to the law of parallax should difTer 

 M by rather more than half the double parallax, I infer, that it is most highly impro- 

 « bable that the longer axis of the ellipse described by parallax shouki , in the brigh- 

 « test Stars , amount to 0",5 of space , and not probable that it should amount to half 

 « this quantity, or to 0",25. And when we consider that the minor axis of this el- 

 « b'pse is only measured in dtclination ( and in a Aquilae this is only equal to half the 

 « major axis); and that, moreover, the star is only deranged from its mean place, 

 « the half of this minor axis , I thjnk it will not be very unsafe to conclude , that eve- 

 « ry attempt to discover the existence of parallax by a mesme in declination , must end 

 « in disappointment. " 



« These observations, continued for many years with the transit Instrument, must in 

 (( the end either detect the existence of parallax , or still more correcüy define its ümits. 

 « But these appear to me even now so small , that I am not disposed to Institute any 

 « farther observations with a view to this parlioular subjeot,, but diall ieave it to be 

 « determined by the regulär course of Observation. " 



« I take this opportunity of stating that the obseryAtiang of « Cy^i j ooiatiaued in the 

 « manner described in a former paper, confirm, ir. !he most decided manner, Ihe total 

 « absence of any observable parallax. They are as follows; 



Gg 2 Win- 



