PREFACE. 



Part I of "Tables of Minor Planets Discovered by James C. Watson," containing tables 

 for 12 of the 22 Watson planets, was published in 1910 in the Memoirs of the National Academy 

 of Sciences, Volume X, Seventh Memoir, with a preface by Simon Ncwcomb, in which he 

 gives an account of the early history of the investigations of the perturbations of the Watson 

 planets under the auspices of the Board of Trustees of the Watson Fund. 



In the introduction to Part I ' reference is made to the Watson planets of the Ilecuha 

 group, for wliich it was found necessary to construct special tables on the plan of Bolilin's 

 tables for the group 1/3. A comparison of these tables with similar tables by v. Zeipel remained 

 to be made before applying either of them to the development of perturbations of planets 

 of the Hecuba group. This comparison was completed in 1913 with the assistance of Miss A. 

 EsteUe Glancy and Miss Sophia H. Levy, with the results set forth in the following pages. 



Publication of these results was delayed, partly because it seemed desirable to verify the 

 tables by application to a number of planets and partly on account of interruptions caused in 

 recent years by war conditions. Miss Glancy, in particular, had undertaken to test the accuracy 

 of our tables, which we had applied to v. Zeipel's example, (10) Hygiea, by further investi- 

 gations on this example after joining the Observatorio Nacional at Cordoba in 1913. This 

 test has now been completed with higlily satisfactory results. The tables have also been 

 successfully applied to the Watson planets of the Ilecuha group, including (175) AndroniacJie, 

 which, on account of unusually large perturbations and other imfavorable conditions, forms 

 so far the most striking example of the applicability of the Bohlin-v. Zeipel method and of our 

 revised tables for the Hecuba group. 



The plan of work included conferences, in which Miss Glancy and Miss Levy took a leading 

 part, for the discussion of the Bohhn-v. Zeipel method, involving verification of all mathe- 

 matical developments and formulation of plans for the construction of tables, and, after the 

 appearance of v. Zeipel's tables, for the comparison of v. Zeipel's original, and our revised tables. 

 The niunerical work was carried out by Miss Glancy and Miss Levy, who have also contributed 

 very largely to the theoretical part of the work, and have prepared the principal details of the 

 manuscript. 



To avoid confusion v. Zeipel's notation and method of procedure have been followed 

 throughout in completing our tables for the Hecuba group, which were well under way when 

 V. Zeipel's memoir appeared. 



To aid computers in the use of the formulae and of the revised tables. Miss Glancy has 

 prepared detailed directions illustrated by an application to (10) Hygiea, the example first 

 chosen by v. Zeipel. These are contained in the first section of the present memoir. 



Miss Glancy's contributions to this investigation and her work on {10) Hygiea were accepted 

 by the University of California in partial fulfillment of the requirements for the degree of 

 doctor of philosophy. 



Miss Levy's contributions and her work on {175) A-ndromacTie were similarly accepted for 

 the same degree. 



It seems highly desirable to make the tables for the development of the perturbations of 

 minor planets of the Hecuba group at once available to astronomers. They are therefore 

 pubhshed herewith, in advance of the perturbations and tables of the remaining Watson planets, 

 as Part II of "Tables of Minor Planets Discovered by James C. Watson." One or two parts, 

 which are to follow, will contain aU the numerical results for the perturbations and tables of 

 Watson planets not pubhshed in Part I (1910). 



This memoir is presented in two sections. The first section, entitled "Formulae and Tables 

 for the Hecuba Group, according to the Theory of Bohhn-v. Zeipel, and an Example of their 



• Pp. 20O-201. 



