POOR, THE FIGURE OF THE SUN 



411 



While the separate determinations vary, a simple inspection of the 

 above table shows that there was a progressive change in the difference 

 between the polar and equatorial diameters. In the earlier measures the 

 equatorial diameter was slightly the greater; in the later measures the 

 polar diameter was decidedly the larger. This is shown not only by the 

 average result, but by the measures of each observer. Adolph, Borgen, 

 Valentiner and Schur made observations in the fall of 1873 and the spring 

 of 1874; again, these same observers made other series of observations in 

 the latter part of 1874 and in January, 1875. In the case of each of these 

 four observers, the difference, P.-E., is greater in the latter series. These 

 results are shown in the foUowino; table : 



Observer. 



1873-74. 



1874-75. 



Adolph 

 Borgen 

 Valentiner 

 Schur 



+ 0".16 

 + 0".21 

 + 0".23 

 + 0".44 



Again, divide the entire series of observations into three groups, placing 

 in the first group all the observations made in 1873, in the second group 

 those made in the spring of 1874, and in the third group those made in De- 

 cember, 1874, and in January, 1875. Give to each observer the weight 

 assigned by Auwers, and form the weighted mean of each of the three groups. 

 The observations then fall into the following order: 



And these means show the same progressive change as do the observations 

 of the separate observers. 



Series of 1880-85. — In this series there are in all thirty-two sets of 

 observations, of which number, however, twenty-three were made in 1882. 

 These are tabulated in Table X, being arranged according to the date of 

 observation in a manner entirely similar to the former table for 1873-75. 



