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ANNALS NEW YORK ACADEMY OF SCIENCES 



Table HI. 



Mean of Years (P.-E.). 



The column "Mean" is from Ambronn; that headed "Weighted Mean" 

 was formed by assigning weights to the observations of Sehur and Ambronn 

 in conformity with the values of the mean error for each year of a single 

 observation as given by Ambronn. Upon the assumption that the shape 

 and size of the sun are constant for each year, Ambronn found, from the 

 separate observations made during that year, the value of the mean error 

 of a single observation, and these mean errors are tabulated in Appendix 

 IV. From these and the number of observations were found by the ordi- 

 nary formulas the weights assigned to the yearly means. 



The observations during the first two years, 1890-91, were made under 

 instrumental conditions different from those during the rest of the interval. 

 In order to find definitive results, therefore, Ambronn forms the means of 

 all the observations, and also means excluding these two years. These 

 means are given as follows: 



Mean of all observation.s 



Mean excepting the years 1890-91 . . 



The final mean as thus given by Ambronn shows that the polar diameter 

 exceeds the equatorial by 



+ 0*'.025 ± 0".018, 



