170 EECENT PROGEESS IlST ASTROISTOMICAL RESEARCH. 



seven years. This result is scarcely yet worthy our complete conflclence, for our 

 observations of earthquakes have only very recently been reduced to proper 

 order ; but if it should turn out to l)e true, it is scarcely necessary to add any 

 words of mine to demonstrate the importance of this rather unexpected result of 

 latitude variation. 



By the beginning of the year 1893 the fact of a variation of hititude 

 was generally admitted, and it was held to be of such importance for 

 the accurate work of geodesy that a long series of exact determina- 

 tions of the variation seemed to be highly desirable. Accordingly, 

 at the meeting of the International Geodetic Association in 1895, it 

 was proposed by Doctor Foerster, of Berlin, that the work should be 

 continued under the auspices of the association. A special fund was 

 raised to defray the expense of the undertaking, and four stations, 

 all within 12 seconds of the same latitude (about 38° 8' N.) were 

 chosen, namely, Carloforte, in the island on San Pietro; Mizusawa, 

 in Japan; Ukiah, in California, and Gaithersburg, in Maryland. To 

 these were soon added Tschardjui, in Siberia, a station supported by 

 the Russian Government, and the observatory at Cincinnati, which 

 offered to join in the work. The first four stations are wholly sup- 

 ported by the International Geodetic Association, excepting that the 

 observer at Gaithersburg is an officer of the U. S. Coast Survey. 

 Very lately the International Geodetic Association has added tw^o 

 stations in the southern hemisphere (at latitude 31° 33' S.), namely, 

 Bayswater, in Western Australia, and d'Oncatwo, in the Argentine 

 Republic. The expense of maintaining the four first mentioned sta- 

 tions and of reducing and publishing the results of observation has 

 been about $14,000 yearly. 



The results obtained are of a very high degree of accuracy, so 

 accurate indeed that a new type of annual variation, having only 

 O.OI" amplitude, has been discovered by the Japanese, Mr. Kimura, 

 in charge of the w^ork at Mizusawa. This interesting new variation 

 is independent of the longitude of the observing station and pro- 

 duces the same effect as would a movement of the center of gravity of 

 the earth to and fro along its axis by an amount of about 6 feet 

 per year. 



The existence of the two principal factors in the variation of lati- 

 tude, substantially as discovered by Mr. Chandler, are fully con- 

 firmed by the observations of the international latitude stations which 

 have now been continued for six years. The period of the principal 

 one is at present thought to be 437 days, however. The accompany- 

 ing figure shows in a graphical form exactly how the earth's axis 

 has been wobbling within the earth in these last six years. It is 

 taken from a recent paper on the subject by Prof. Th. Albrecht, who, 

 with Dr. B. Wanach, has reduced and published the international 

 observations. In the figure the scale of motion is indicated in seconds 



