132 



TUCKER— EFFECT OF DIURNAL VARIATION 



star at all hours of the day, but the observations of Polaris include 

 many consecutive transits at opposite culminations. 



The variation in clock corrections or rates is distinctly of a 

 diurnal character. 



Diurnal Term in Latitude Variation. 



The groups of A have an average above 42 observations each. 



The probable error of the night groups derived from individual residuals 

 is + o".o8, and that of the day groups is + o".i2, average + o".io. 



The two sunset groups have residuals of four times the average 0-C, 

 which would be + o".o6 if these two results are combined into one. 



Observations. 



Zenith stars 258 



a. Andromeda 135 



Polaris 231 



/3 Urss Minoris 77 



Groups 319 



