10 



Art. 3 - K. Sotomu: 



effoct varies witli the difference of temperature between the body 

 and the instrument, tlie (hsturbance would vary inversely with the 

 temperature, i.e., it would be greater in winter than in summer. 

 This sequence agrees well with the observed plienomenon, and wo 

 may take this thermal effect as one cause of the behaviour of the 

 zenitli telescope. 



Witli respect to the third cause, I may notice the fact that tlie 

 horizontal pendulum observers in several parts of the world have 

 revealed a remarkable unsteacHness of the ground. Tlie most con- 

 spicuous of the regular movements has a period of one solar day, 

 being due to the effect of the solar radiation on the earth's surface. 



E, von Rebeur-Paschwitz did pioneer work with the horizon- 

 tal pendulum of his original form at Karlsruhe (1887), Strassburg 

 (1892-94), and Nicolaiew (1892), to the effect that the pendulum 

 swinging in the prime vertical showed a regular movement in the 

 period of one solar day, and took the soutliernmost position in the 

 evening and the northernmost position in the morning, as is here 

 shown, — ^^ 



Table III. 



Component in the meridian (pendulum swinging in tlie prime 

 vertical) North +, Soutli — . 



1) .\strunoinische Nachrichten, Nr. 3148. 



