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INTRODUCTION. 



With approximately one thousand asteroids discovered and believed 

 to be sufficiently observed to permit of fairly reliable orbit determina- 

 tions, as indicated by the permanent numbers assigned to them, the 

 task of preserving these discoveries has grown so stupendous that the 

 time seems to have arrived for an analysis of the present astronomical 

 practice in providing the necessary additional observations and 

 calculations. 



Hitherto, the burden of correcting orbit elements and computing 

 ephemerides has rested principally on the Berlin Recheninstitut. In 

 recent years the Marseilles Observatory has rendered notable service 

 in contributing orbits and ephemerides. Observations, photographic 

 and visual, are regularly made at a number of observatories. The 

 Berlin Recheninstitut publishes ephemerides and other results in the 

 Astronomische Nachrichten, and in the Ephemeriden der Kleinen 

 Planeten. Up to 1918 these data appeared also in the Astronomisches 

 Jahrbuch. The number of oppositions during which the minor planets 

 have been observed, and the status of orbit determinations are an- 

 nually summarized in the Viertelj ahrschrift der Astronomischen Gesell- 

 schaft. In 1901 Bauschinger published the latest reliable elements, etc., 

 with data concerning the perturbations for the then known 463 planets, 

 "Tabellen zur Geschichte und Statistik der Kleinen Planeten." 



The latest available collection of elements is contained in the 

 Berlin Jahrbuch for 1918. The adopted Jahrbuch elements serve the 

 purpose of providing ephemerides from opposition to opposition. 

 Their origin may be traced from the notes given from year to year 

 in the Jahrbuch, ending with 1918, and in Kleine Planeten. Some of 

 the elements include arbitrary corrections to the mean motion and 

 to the mean anomaly for the purpose of representing late oppositions 

 so as to serve for prediction of immediately following oppositions. 

 In other cases, approximate or accurate perturbations are included, 

 with or without correction of the elements by the usual least squares 

 adjustment. For thirty-six planets the elements in the Jahrbuch of 

 1918 are mean or osculating elements, derived in connection with 

 general perturbations which are approximately included in the pre- 

 diction of ephemerides. Until similar fundamental data shall have 

 become available for the remaining planets, the present practice of 

 the Recheninstitut appears to furnish the only certain method for 

 the preservation of planetary discoveries. 



