539 



The result of Newcomb's discussion in 1891 of all available deter- 

 minations of the constant of nutation has determined its value to 

 about \', 1(100 ^f '^'^ amount. To get a p.e. of ± 0".005 in /> this 

 accuracy uiust be increased nine- or tenfold. This certainly is no 

 easy task, but it would be preposterous to say that it exceeded the 

 forces of astronomy. It will of course require very refined and 

 prolonged observations and discussions. 



I may be allowed to remark that it still remains to be investigated 

 whether the new precession is the only effect of the new gravitational 

 theory, and the equations (J) and (2) are not affected, i.e. whether 

 Einstein's theory gives exactly the same equations for the motion of the 

 axis of rotation of the earth with reference to thegeodetically transported 

 system of coordinates, as are found in Newton's theory relatively to 

 a "fixed" system. This cannot be asserted without a special investi- 

 gation, which so far as 1 know has not been undertaken, and it 

 might even happen that the precession of the geodetically transported 

 systeui of coordinates was exactly cancelled by a small change in 

 the precession of the earth relatively to that system. 



