VARIATION OF LATITUDE. 277 



Here, tben, was evidence of a comparatively rapid cliange in lati- 

 tude. New observations were undertaken at Berlin, Potsdam, Prague, 

 and Bethlehem, Pa. (all by Talcott's method), and all agreed in show- 

 ing plus and minus changes in latitude for the years 1888-1800. 



There were still some doubters. Moreover, it was decided to crit- 

 ically test the matter by sending an exj)edition to the Sandwich 

 Islands, which is 180 degrees (nearly) in longitude from Berlin. If it 

 were known the latitude of Berlin increased, then a point in the 

 Northern Hemisphere 180 degrees away from Berlin should simulta- 

 neously show a decrease in latitude, for if the pole move toward Berlin 

 it must move from the point on the other side of the earth. 



Our own Government joined in the effort. Marcuse, of Berlin, and 

 Preston, of Washington, spent more than a year on the Sandwich 

 Islands observing for latitude, while at the same time observations 

 were continued at Berlin, Prague, and Strasburg in Europe, and at 

 Eockville, Bethlehem, and San Francisco in the United States. The 

 results of all these observations have been published, and show, with- 

 out a chance of error, that the earth's axis is moving, that the lati- 

 tudes at the Sandwich Islands increased when the latitudes in 

 Germany diminished, and vice versa. 



The law of the change was eagerly and industriously sought for by 

 some of the ablest mathematical astronomers of the world. They 

 first worked on the idea that the changes must conform to the 30o-day 

 period of Euler, combined with an annual change due to causes set 

 forth by Sir William Thomson, and which I have previously mentioned. 

 None of these investigations have given a satisfactory formula for the 

 prediction of the latitude of any place. 



In 1891 Dr. S. C. Chandler, of Cambridge, Mass., began his investi- 

 gation of the problem. He remarks: 



"I deliberately put aside all teaching of theory, because it seemed to 

 me high time that the facts should be examined by a purely inductive 

 process ; that the nugatory results of all attempts to detect the existence 

 of the Eulerian period (of 305 days) probably arose from a defect of 

 the theory itself, and that the entangled condition of the whole subject 

 required that it should be examined afresh by processes unfettered by 

 any preconceived notions whatever. The problem which I therefore 

 proposed to myself was to see whether it would not be possible to lay 

 the numerous ghosts in the shape of various discordant, residual phe- 

 nomena pertaining to deteruiinationsof aberration, parallaxes, latitudes, 

 and the like, which have heretofore flitted elusively about the astronomy 

 of precision during the century, or to reduce them to some tangible form 

 by some simple consistent hypothesis. It was thought that if this could 

 be done a study of the nature of the forces as thus indicated, by which 

 the earth's rotation is influenced, might tend to a physical exj)lauation 

 of them." 



Dr. Chandler proceeded to examine his own work with the Almucan- 

 tar at Cambridge, the observations of Klistner, Gylden Nyren, the 

 Washington observations, and others. He found that they all seemed 



