6 CELESTIAL MECHANICS: LEUSCHNER 



intended to serve as illustrations of the data which should be made 

 easily accessible. No claim is made for the absolute completeness of 

 these data. The time for active work, with the aid of a few assistants, 

 to prepare these preliminary surveys has extended only over a little 

 more than a month. A great mass of material had to be consulted 

 which was found to be of no importance to the purpose in hand.. This 

 is being preserved on cards for easy reference, if required at any time. 

 Thus care has been taken to eliminate elements which would not be 

 considered as fairly accurate osculating elements particularly those 

 which have resulted from corrections on the basis of subsequent 

 oppositions purely for ephemeris purposes, without complete con- 

 sideration of the perturbations and of the earlier oppositions in the 

 final adjustment. This policy, however, has not been adhered to 

 strictly, partly for historical and theoretical reasons with reference to 

 preliminary elements, and partly for other reasons with reference to 

 later elements. 



Whenever possible, the reasons for the abandonment of previous 

 investigations are given, but in many cases no reasons could be found, 

 at least not in the astronomical records available in the library of the 

 University of California. Some of these reasons are probably to be 

 found in the records available in the library of the Lick Observatory, 

 but in the limited time it has not been possible to consult these or 

 other additional records for this preliminary survey. An immense 

 amount of fundamental work has been accomplished by the Berlin 

 Recheninstitut, particularly in computing special perturbations and 

 deriving osculating elements, but has been published only in part. 

 The remainder reposes in the archives of the Recheninstitut. It may 

 be assumed that the immense task of providing ephemerides has 

 interfered with the publication of the accumulated material. With- 

 out this material, research surveys such as those presented here are 

 not complete. 



A simple way of accomplishing the introduction of the improved 

 mass of disturbing planets referred to above, is to multiply the final 

 sum of all the terms for each component of the perturbations by the 

 ratio of the new to the old mass. Aside from the improvement which it 

 may be possible to make to some of the older fundamental data, par- 

 ticularly those which are no longer used for ephemeris purposes, by 

 the introduction of the best determined values of the masses of the 

 major planets, it is probably possible to enhance their values still 

 further by correcting the elements on the basis of the existing develop- 

 ments of the general perturbations, with the aid of subsequent 

 oppositions and in case of appreciable changes in the elements, by 



