JOURNAL OF THE COLLEGE <iF SCIENCE, TOKYO IMTEIUAL UNIVERSITY. 



VOL. XXXVII., ARTICLE 3. 



Considerations on the 

 Problem of Latitude Variation. 



By 



Kiyofusa SOTOME, Pii'jahnshi, 

 Assistant Professor of Astronomy, Tokyo Imperial University. 



Introduction. 



Tins paper covers some studies on the zénith telescope as an 

 astronomical instrument extensively used in observing the varia- 

 tion of latitude. Herein the writer intends to call attention to tlie 

 fact that there are, according to his experience, some remarkable 

 phenomena in the behaviour of the zenith telescope, and further, 

 to show the possibility of finding a method of explaining the z-term 

 and closing sum (schlussfehle]") in the variation of latitude in con- 

 nection with tliese phenomena. The development is made in the 

 foll()wi]\g tliree sections. 



I. Singular behaviour of the zenith telescope. 



During the years l'.JU()-lUn, the writer was in charge of the 

 observations of latitude variation in the Tokyo Astronomical Obser- 

 vatory^, under the auspices of the Geodetic Committee. This was 

 in continuation of the series of observations made successively by 

 Professors 11. Kimura and K. llirayama. The instrument used 

 was a zenith telescope of the usual form, made hy Wanschaff in 

 Berlin, No. 8U0, aperture 8r'""- and focal length lOO'""- . 



In order to determine the value of one turn of the micrometer 



