A. Hall— Variations of Latitude. 227 
This is a very good agreement of the results, and it is worth 
while to notice that the parallax of the pole star comes out 
positive from each series, and that the resulting value of the 
constant of aberration agrees well with the best determina- 
tions. An investigation made by Mr. A. M. W. Downing of 
the latitude of Greenwich from the observations for the ten 
years 1868-1877 gives 
p=0":075 + 0"°015. 
pcos §=—m™ 
psin >= +72, 
‘ust judge whether the results are harmonious and really 
Probable. Reducing the values of € to a common epoch, the 
‘agreement is not good. We infer, therefore, that these investi- 
8tions do not indicate with any certainty a variation of lati- 
tude having the period of 805 days. 
tom what precedes it appears that observations do not 
Prove that latitudes are variable, and the evidence points rather 
"sons, Perhaps some of these may 
which are in common use, an 
Order to detect the variations of latitude which we know must 
very small. 
at te not th which latitudes are 
uncommon to exaggerate the accuracy with whic : 
— have only to pei our ephemerides to find much larger oe 
giv, than the probable errors will warrant. Thus the latitudes of Greenwie 
Nac the Berliner Jahrbuch and the American Ephemeris differ by 0°°3. 
aval Observatory, 1885, January 21. oe 
