EECENT PROGRESS IN ASTRONOMICAL RESEARCH. 167 



far from being insignificant that a number of observatories have 

 been founded by international cooperation whose principal function 

 is the accurate study of this phenomenon. These international lati- 

 tude observatories have been in full operation for six years, and 

 interesting results of their work are now published. 



While the possibility of latitude variation was recognized from the 

 careful work of European observers as early as 1885, the actual dis- 

 covery of the variation and of the laws which govern it are the work 

 of an American astronomer, Mr. S. C. Chandler, carried through in 

 the face of the opposition of long-accepted theory and of the opin- 

 ions of astronomers in general. It will be interesting to recall 

 briefly some of the steps and conclusions involved in this -remarkable 

 discover}'. 



The phenomenon in question has, of course, no connection with pre- 

 cession or nutation, but is concerned only Avith a A'ariation of the posi- 

 tion of the axis of rotation of the earth Avithin the earth itself. Its 

 effect is to j)eriodically increase the latitude of places on one side of 

 the earth and simultaneously diminish that of those on the opposite 

 side of the earth by amounts of the order of 30 or 40 feet. In other 

 words, the pole is 30 or 40 feet nearer Washington, and the same 

 farther from Peking at one time than another. 



Mr. Chandler's first announcement of his discover}?" in 1891 began 

 as follows : 



lu the determination of the latitude of Canilnidge (Mass.) with the Almu- 

 cautai" about six years and a half ago, it was shown that the observed values, 

 arranged according to nights of observation, exhibited a decided and curious 

 progression throughout the series, the earlier values being small, the later ones 

 large, and the range from November, 1884, to April, 1885, being about four- 

 teuths of a second. There is no known or imaginable instrumental or personal 

 cause for this phenomenon, yet the only alternative seemed to be an inference 

 that the latitude had actually changed. This seemed at the time too bold an 

 inference to place upon record, and I therefore left the results to speak for 

 themselves. * * * 



He gives further data of his own on the subject tending to support 

 the hypothesis of a change of latitude, and then refers to European 

 observations contemporaneous Avith his OAvn as folloAvs : 



Curiously enough Doctor Kiistner, in his determination of the latitude from 

 a series of observations coincident in time with those of the Almucantar, came 

 upon similar anomalies, and his results, published in 1888, furnish a counter- 

 part to those I had pointed out in 1885. The verification afforded by the 

 recent parallel determinations at Berlin, Prague, Potsdam, and Pulkowa. which 

 show a most surprising and satisfactory accordance as to the character of the 

 change in range and periodicity with the Ahnucantar results, has led me to 

 make further investigations on the subject. * * * 



Mr. Chandler then proceeded to giA^e detailed results of the iuA^es- 

 tigations, which he summed up as foUoAvs: 



The general result of a preliminary discussion is to show a revolution of the 

 earth's pole in a period of 427 days, from west to east, with a radius of 30 



