( 45 ) 



«—2412438 

 ?/ = — O .143 sm 2 71 ^^ 



in which the epochs are expressed in Julian dates. 

 By these my 8 means are represented as follows: 



Albrecht assumes 0".04 as mean error of his co-ordinates, 

 according to which that of the mean of 9 values, with which we 

 operated here, would be 0".013. 



We thus see that the amplitudes found foi' m and y are very 

 nearly equal and that the diiforonce of phase amounts to 90° with 

 the difference of only a single day. The motion thus proves to be, 

 with considerable approximation, circular and to be direct, that is 

 with the rotation of the earth from west to east. 



To determine the length of the period these results must be 

 united with the results of anterior observations. For that purpose I 

 did not retain the whole of the data used by H. G. v. D. Sande 

 Bakhuyzen, but chose only the most certain results, namely those 

 from Leiden 1864—1874 and those from Pulkowa 1882—1892, 

 for which the mean errors are by far the smallest. So I obtained 

 as epochs of maximum of .f, == epochs of maximum of the latitude 

 for Greenwich : 



