ADVISORY COMMITTEE ON ASTRONOMY 1 5? 



comparison of the best tables of Mars with all the good existing ob- 

 servations of that planet. This work is beyond the power of an 

 individual, and is, therefore, of the class which can most properly 

 be supported b}^ an institution. 



Passing now to the fixed stars, the foundations of a new science 

 of stellar statistics are being laid. The pursuit of this science 

 requires a ccnibination of all the observations and methods of stellar 

 research in both the fields of astrometry and astrophysics. To the 

 very able and coniprehensive survey of the subject by Professor 

 Boss I wish to add the following considerations : 



It seems to me essential that whatever aid the Carnegie In.stitutioR 

 may give to researches in this class should be so applied as most 

 eltectively to gain the desired end. Among these ends that which 

 must take the first place, so far as quantity of labor and need for help 

 are involved, is the determination of the motions of as many stars 

 as possible in every part of the sky. F6r this purpose it is essential 

 that the researches of Professor Boss be supplemented by a re-reduc- 

 tion of certain series of former observations. The necessity of this 

 arises from the fact that the proper motion of a star can, in most 

 cases, be determined only by a comparison of observations as widely 

 separated as possible. 



The observations which most need re-reduction are the following : 



1. The observations made at the Royal Observatory, Greenwich, 

 by Maskelyne, from 1765 to about 1816. These observations have 

 been neglected, owing to their having been made with an imperfect 

 instrument, but it is believed that, with but little labor, they could 

 be so reduced as to be made useful to astronomy. It would seem, in 

 fact, that the office of the American Nautical Almanac was able to 

 reduce mos( of them in a provisional way with the very limited 

 means at its disposal. But it is desirable to have the work carried 

 through more thoroughly. 



2. The Greenwich observations by Pond, especially those of decli- 

 nation, have been shov^^n by Chandler to be of the highest degree of 

 precision. Those which he has provisionally reduced already form 

 a valuable contribution to exact astronomy. It seems desirable that 

 the work of reducing them should be completed. 



3. Tlie observations by Piazzi at Palermo, about the end of the 

 eighteenth and beginning of the nineteenth century, are celebrated 

 in the history of astronomy. Their re-reduction has been one of the 

 desiderata of astronomy for half a century and the necessitj' for it 

 has frequently been pointed out. Quite recently the work has been 



