TABLES OF MINOR PLANETS DISCOVERED BY JAMES C. WATSON. 



By Armin O. Leuschner. 

 PREFACE. 



By the will of James C. Watson, who died in 1880, a fund was bequeathed in trust to the 

 National Academy of Sciences for the purpose of promoting astronomical research. Objects 

 specifically designated were the awarding of a medal not oftener than once in two years for 

 important astronomical works and the construction of tables of the minor planets discovered 

 by the testator. The expenditures were to be made under direction of a board of three trustees. 

 The first board was named in the will, the members being J. E. Hilgard, John H. C. Coffin, 

 and Simon Newcomb. At the present time, March, 1908, the members of the board are: 

 Simon Xewcomb, chairman: William L. Elkin, and Lewis Boss. 



The construction of the tables was long delayed by the difficulty of finding computers 

 competent to carry the work through in a satisfactory way. To lessen this difficult} - an 

 arrangement was made with Prof. E. Becker, director of the Strassburg observatory, for sup- 

 plying a complete form for computing the perturbations according to Hansen's method, in 

 which the eccentric anomaly was taken as the independent variable. An example was also 

 supplied lr\ T Professor Becker in the form of a computation of the perturbations of Eurynome by 

 Jupiter. Tables of Minerva were completed and published on this plan by Dr. W. S. Eichel- 

 berger. 



The conclusion subsequently reached was that the system of employing the eccentric 

 anomaly was not a desirable one, and that it was better to adhere to the use of the time as the 

 fundamental variable. Several experts were engaged in computing the perturbations of different 

 asteroids by Jupiter under the general direction of the writer, but in no case except that of 

 Minerva were the processes of tabulating the perturbations and correcting the elements brought 

 to a satisfactory conclusion. 



The slow progress of the work made it evident that it must be prosecuted in a more sys- 

 tematic way under the personal direction of a leader who would bring it to a conclusion. After 

 a careful survey of the field, Prof. Armin O. Leuschner, of the University of California, was 

 selected as the leader, and all the papers were placed in his hands. He undertook to construct the 

 tables with the aid of the students and assistants in the Berkeley Astronomical Department of the 

 University of California. The system agreed upon was that the tables should be carried only to the 

 degree of precision necessary for finding ephemerides. The only perturbations then required 

 would be those of the first order by Jupiter, though approximate quantities of higher order 

 would in some cases be advisable. The construction of even these approximate tables proved 

 vastly more laborious than had been expected, owing to circumstances set forth by Professor 

 Leuschner in the introduction. As the general outcome of the work up to the present time, 

 tables of twelve of the asteroids in question are herewith presented, with the hope that they 

 will be sufficiently accurate for as long a period as if entire theoretical precision had been aimed 

 at in their construction. The remaining tables are in an advanced state, and it is expected 

 that they will be completed and published at no distant day with the single exception of Aethra 

 which must await rediscovery. 



Simon Newcomb. 



Washington, 190S, March. 



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