204 REPORTS ON INVESTIGATIONS AND PROJECTS. 



MERIDIAN ASTROMETRY* 



By lyEwis Boss, Director of the Department. 



At the annual meeting of the Trustees of the Carnegie Institution of 

 Washington, December, 1905, an appropriation was made to enable the writer 

 to execute the various observations and computations relating to the motions 

 of all stars down to the seventh magnitude, including, also, all stars observed 

 with precision during the first half of the nineteenth century. This was 

 done with the understanding that a like appropriation would be made annually 

 for ten years in order to complete the work under contemplated plans. 



This work is essentially an extension of that for which the Institution has 

 been appropriating annual grants to the writer during the last three j'ears. 



Associated with all such investigations of considerable extent is the thought, 

 more or less definite, that general conclusions of more than ordinary impor- 

 tance may be developed as a consequence of the new knowledge to be disclosed. 

 Sometimes the nature of the final outcome from an extensive investigation 

 has been entirely unforeseen. It must always be regarded as a fortunate 

 circumstance, however, when such an investigation has in view from the 

 beginning a specific and tangible object, the attainment of which will alone 

 constitute a sufficiently useful result to justify the effort involved in its 

 attainment. The present investigation has such an object. 



The Department of Meridian Astrometry is designed to give an impulse to 

 the study of stellar motion. In order to do this effectively it aims to be 

 critical as to the motions themselves and comprehensive in its field of opera- 

 tions. In these two aspects of its work there are natural limits imposed by 

 questions of practicability. For more than one reason it is desirable that 

 the investigations shall cover stars down to the seventh magnitude. Inves- 

 tigators and practical observers in various lines are continually desirous of 

 information as to the positions and motions of stars of this class. It is 

 desirable that in this age of the scientific world we take account of stock as 

 to the vast effort which has been expended in precise observations of star- 

 positions. The class of stars we are considering has constituted the field 

 of such effort. It would be interesting to see what can be learned from a 

 study of accurately determined motions of from 15,000 to 20,000 stars in 

 relation to which the accumulated material of observations is of greatest 

 weight. 



The point which should be held clearly in mind is that the first requisite 

 in the program of the Department of Meridian Astrometry is to ascertain 

 what are the systematic secular motions of the stars in general. There are 



* Report for the year ending September 30, 1906. Grants Nos. 319 and 368. |28,ooo. 

 Study 0/ motion and structure of the stellar system. (For previous reports see Year Book 

 No. 2, p. XVIII ; Year Book No. 3, p. 85, and Year Book No. 4, pp. 78-82.) Grant No. 368, 

 for ^20,000, was not used during the year. 



