( 43) 



sirable first to make endeavours to derive information from other 

 sources. 



Since in 1891 the 14-monthly period in the motion of the Pole 

 of the earth had been found by Chandler, many computations 

 have been made on that subject by him. On the other hand the 

 chief series of observations of the hist 50 years were submitted by 

 H. G. V. D. Sande Bakhüyzen ^) in 1894 to a searching and 

 complete examination, in which the result of the Leiden observations 

 of the years 1864—1874 obtained by Mr. Wilterdikk's ~) elaborate 

 researches, as compared to those of the other observatories, proved 

 to be entitled to considerable weight. 



Meanwhile a beginning had been made with special series of obser- 

 vations having expressly in view the investigation of the problem 

 of the latitude and soon important results were furnished by the 

 voluntary co-operation of a number of astronomers. More than once 

 Prof. Albrecht has summarised those results in the reports of the 

 "International Geodetic Survey" and of late an ample report has 

 been given by him about the state of the problem in Dec. 1897 ^), 

 in which he adjusted the whole series of the obtained results by a 

 continuous curve for the motion of the pole. 



But a small part of these results could yet be used by H. G. v. D. 

 S. Bakhuyzen and though it be true that Chandler has already 

 made many computations on this subject, yet often there is a lack 

 of judgment in the treatment of the observations, which in my 

 opinion justifies a new investigation covering now the whole of the 

 period of 1890—1897. The results I found being perhaps of some 

 importance apart from the particular aim for which I undertook 

 my investigation, 1 take the liberty of making them the subject of 

 a concise communication. 



2. Albrecht could use the observations of 19 observatories, viz : 

 of Tokio, the Cape of Good Hope, 10 observatories in Europe, 6 in 

 America and finally Honolulu, a temporary observatory having been 

 erected there in 1891—1892. With a few exceptions the observations 

 have been made according to the Horrebow method. Not in a single 

 place however do they cover the whole period, so Albrecht had to 

 undertake extensive computations to derive in successive approxima- 



') Report of the Meetiug of the Roy. Acad. Amsterdam, Febr. 1894 aud also 

 Astr. IQac.hr. vol. 136 and 137. 



2) Report of tlie Meeting of the Roy. Acad. Amsterdam, Dec. 1893. 



3) Th. Albeecht, Bericht iiber den Stand der Erforschung der Ereitenval-iation 

 m December 1897. 



