CXX J! COMPARISON-STARS. 



For stars observed with Mars II : 



T Santiago = 0".120 0".091 from 41 observations. 



T _ Bessel = + 0".471 0".293 from 32 observations. 



rp Maclear = 1".325 0".234 from 13 observations, excluding one, (Pollux.) 



T Greenwich = 0".056 0".206 from 6 observations, excluding one, (N- 100.) 



T Washington = 0".238 d= />".054 from IT observations, excluding one, (N- 95.) 



For stars observed with Venus I : 

 T Washington = + F.696 0".114 from 38 obs., or excl. 4, (N os - 112, 127, 141, 144,) 



= _j_ l".727 0".064. 

 T Argelander = + 0".063 0".276. 

 T Ann Arbor = + 3".348 0".261. 



For stars observed with Venus II : 

 T Bessel = + 0".136 0".096. 



The large values of the differences for the observations taken from Bessel's Zones need not be 

 considered as implying any deviation from Bessel's standard, but are, in every case, traceable 

 to deviations of particular zones made manifest by comparison with at least two independent 

 authorities. 



This discordance or deviation is especially evident in zone 2*75, as will be clearly seen on 

 collation of the equations, which are deduced after the omission of comparisons with the stars of 

 this zone. Thus, the value of (Santiago Bessel) which, by the use of all thirty-one differences, 

 was found to be -(- 0".565 rt 0".380, was reduced, after exclusion of the four differences dependent 

 on zone 275, to + 0".141-=fc 0".363. So also the value of (Washington Bessel) which, if the 

 places from zone 275 be employed, is = -j- 0".44 =t 0".59, becomes, after rejection of these, 

 = 0".06 0".53. And of the three series for Mars I, into which these stars enter appreciably, 

 the equations above given are changed by the omission of this zone to the following : 



T Santiago = 0".089; 0".086. 

 T Washington = + 0".1T6 0".056. 

 T Bessel = + 0".163 0".287. 



The correction apparently due to these stars is, if constant, about 3", but the observations are 

 much better satisfied if the correction be supposed to change with the time. Since none of the 

 places from this zone are absolutely necessary for our purpose, they have been omitted in taking 

 the final mean, although given in the list for comparison. A somewhat similar case is that of 

 zone 405, which has, however, been retained. 



From examination and combination of these results, the equations have been ultimately 

 determined which are to be used in connection with the declinations, as furnished by the 

 observatories under consideration. 



They are as follows, and have been uniformly applied to all measured declinations, whether 

 of star or of planet. The reductions applied to star-places from other sources are employed as 

 cited on page cxx. 



T - - Washington = 0".5 for stars observed with Mars I. 

 T- 0".2 Mars 11. 



T " = + 1".7 " Venus I. 



T Santiago = 0".l 

 T Greenwich = 



- Maclear = 0".6 for stars observed with Mars I. 

 T = l"-3 " Mars II. 



The declinations from Bessel's Zone 275 are not employed for the mean. 

 The annexed Final List of places of comparison-stars gives for each star the several authorities ; 

 the number of observations from each, both in right-ascension and declination, these numbers 



