( 285 ) 
Let the correction for the periodical error of division in a 
reading «, be 
asin2a Jb cos 2 a 
as more than 2 terms cannot well be determined. 
If we assume that in each position the mean zenith distance is 
53° the influence of the errors of division on the ares of 106° 
measured is: 
a {sin (2 p + 106°) — sin (2 p —106°)} HL {cos (2p +- 106°) — cos (2p—106°)} 
= 2a sin 106° cos 2 p—2 b sin 106° sin 2 p 
while the influence of the flexure of the telescope on the zenith 
distance will be csin 53°. Hence we may represent the differences 
N—S found above, by a formula: 
N—S=c' + a'cos2p-+ b' sin 2 p 
and we find 
== Bean 53° = —0".96 
a’ = 2asin106° — —8",94 
b' = —2 bsin 106° = +1".71 
whence: 
ee (60 
a = —4.65 
b = —0.89 
Finally we find: 
Corr. for Division errors = +4".74 sin (2 a—169°. 2) 
Corr. for Flexure = —()"60 sz 
and it is found that after having applyied these corrections, the mean 
results for the different positions are in good agreement. 
The correctness of these formulae may be tested by the results 
of an observation of y Crucis on May 15, not considered before, 
