Vol.. 8, 1922 
ASTRONOMY: A. 0. LEUSCHNER 
171 
were later corrected on the basis of oppositions extending from 1868 to 
1874 with consideration of the special perturbations by Jupiter and Saturn. 
These elements have been carried forward with perturbations until 1898 
and from that time on until 1920 without change of osculation. For 1920 
the elements were improved by the Berlin Recheninstitut by a slight cor- 
rection of the mean motion so that the last 14 oppositions appear to be 
represented with an accuracy of ±3'. In the mean time, however, ob- 
servations extending from 1915 to 1918 had revealed increasing discrepan- 
cies between the observations and computed places. On October 9, 
1918, this discrepancy amounted to nearly 2V2° in right ascension and 1° 
in declination. These discrepancies have led to new orbits and ephemerides 
by Blondel, Maitre and Jehkowski, published in the Bulletin of the Ob- 
servatory at Marseilles and to the latest revision of the elements by the 
Berlin Recheninstitut. These latter elements will no doubt represent 
observations at the next few oppositions with a satisfactory degree of 
accuracy, provided the laborious computation of the special perturbations 
and the correction of elements from opposition to opposition is kept up. 
Otherwise large discrepancies are bound to reveal themselves again in the 
course of a few oppositions. Even then, this piece-meal procedure does 
not produce a set of elements or a theory of perturbations which will 
represent the observations in all of the oppositions from 1849 to the pres- 
ent time and for at least an equally long interval in the future. 
Aside from the enormous amount of computation of temporary value 
which is involved, it is necessary to secure frequent observations in order 
to secure the data for the successive improvement of the elements and 
perturbations. Thus, during the last ten years, more than 100 accurate 
photographic and visual observations of Hygiea have been published. 
These difficulties may now be wholly overcome by the application of von 
Zeipel's revised Jupiter perturbations of planets for the Hecuba Group and 
by the application of similar tables to other groups as originally proposed 
by Bohlin. As stated above, von Zeipel developed the perturbations of 
Hygiea from his original tables on the basis of von Zech's elements. With 
these perturbations he represented oppositions from 1849 to 1884. This 
representation showed a constantly increasing discrepancy which in 1884 
had reached 23' in right ascension and 9' in declination. He therefore 
corrected the elements by the method of least squares and thereby suc- 
ceeded in representing the observations satisfactorily until 1914. Dis- 
crepancies will hereafter rapidly increase in the opposite direction. The 
original discrepancies were not due so much to inaccuracy in von Zech's 
elements as to some inaccuracies in von Zeipel's tables for the Hecuba 
Group. This is clearly shown by the fact that von Zech's unchanged 
elements and our revised tables give as satisfactory a representation in the 
37 years from 1884 to 1921 as in the preceding 35 years from 1849 to 1884, 
