126 CARNEGIE INSTITUTION 



Loewy method ; by Professor Rees at Columbia, and by Professor 

 Doolittle at the University of Pennsylvania, using the zenith tele- 

 scope, and by Professor Asaph Hall, Jr., at Ann Arbor, from 

 meridian circle observations. The discordance of the results seems 

 to render it desirable that further determinations should be made. 

 Quite recently Dr. Chandler has carried on a series of critical inves- 

 tigations by computation upon all the series of observations avail- 

 able in the discussion of this cons;tant, and he has arrived at con- 

 clusions of remarkable interest. 



Constant of Precession. 



The constant of precession is also of very great fundamental im- 

 portance in its bearing upon the entire range of astronomy of pre- 

 cision as well as upon the testimony upon which we must ultimately 

 rely for our investigation of the mechanism of the universe. This 

 constant, however, stands in such intimate relation to the solar mo- 

 tion that the discussion of the two is practically inseparable. Special 

 observations for determination of this constant are not necessary. 



It should be mentioned that in Professor Newcomb's great work 

 upon the planetary system he devoted much attention to the evalu- 

 ation of a series of astronomical constants which should be consistent 

 with each other and as precise as possible upon the basis of the ma- 

 terial of discussion available to him. These constants have been 

 generally adopted in the construction of astronomical almanacs ; and 

 it is characteristic of the rapid progress of astronomy that there has 

 been no time within the memory of living astronomers when there 

 has been apparently less satisfaction in the existing values of those 

 constants which have been adopted. This is not because Professor 

 Newcomb's results are not an improvement upon what had gone 

 before, but because of the rapid accumulation of material of observa- 

 tion which points to the chance of deriving more reliable values, 

 corresponding to the more exacting demands of astronomy. 



Related I^ines of Research. 



From an analysis of the foregoing, it will be seen that there are 

 several related lines of investigation pressing for attention, all bear- 

 ing upon a distinct problem — that concerning the structure of the 

 sidereal universe. 



Of ver>' high importance in discussing the minute motions of the 

 stars is it that the observations of position should be freed from their 



