10 CELESTIAL MECHANICS: LEUSCHNER 



The form in which the research surveys are presented must be con- 

 sidered experimental. That adopted is the outcome of several other 

 attempts at presenting the material. It is hoped that this report will 

 call forth helpful criticisms and suggestions which may ultimately 

 lead to the adoption of some definite plan for international coopera- 

 tion. Much material has been collected on planets not included in the 

 list, which, it is hoped, may be printed later. 



It was found that the research surveys for the various planets could 

 not be made so complete that the investigator may abstain from 

 referring to the sources themselves. This applies also to the collection 

 of elements. The elements are collected merely for purposes of com- 

 parison and are not reproduced with uniform accuracy. 



For practically all the planets in the list, except the first four and 

 several others, a fairly complete bibliography of observations has 

 been prepared, but this bibliography is published here only for the 

 last two of the Trojan group. 



Attention might well be called here to the need of curtailing 

 indiscriminate observations. Even in recent years observations have 

 been multiplied for planets for which two or three accurate observa- 

 tions at each opposition would be sufficient for all scientific purposes. 

 It is planned to formulate in the near future definite proposals for 

 an international program of observations. 



The main purpose of this report is the encouragement of funda- 

 mental researches essential to the ultimate aims of astronomical 

 science, which, for their consummation, require the knowledge of 

 accurate elements and perturbations of the minor planets. 



The surveys have been prepared in the main by Dr. W. F. Meyer, 

 and by Dr. H. Thiele, assisted by several advanced students in 

 astronomy, who have gathered the necessary references. For the 

 Trojan group, unpublished data collected by Dr. Sturla Einarsson 

 have been available. 



As a rule the abbreviations adopted for the references are those of 

 the Astronomischer Jahresbericht. 



The usual notations of the elements are adhered to, both ^ and n 

 being used for the mean daily motion. 



