Considerations on the Problem of Latitude Variation. 



I. Tlic displacement of bul:)bles is entirely due to some cause 

 in the level itself, and is not due to the variation uf inclin- 

 ation of the telescope. The telescope did not move 

 during the observation. 



II. The displacement corresponds exactl}^ to tlie change of in- 

 clinition of the telescope. This is the assumption usually 

 adopted. In the reduction, thechange between tworeadings 

 \ya< considered to be proportional to tlie time interval. 



AVith the first assumption, western elongation gave a greater 

 value of tlie micrometer than eastern elongation; witli the second 

 assumption, on the contrary, eastern elongation ga\'e a greater 

 value than western elongation.' This fact is easily seen from the 

 series of observ^ations during February-March lOliJ, in the follow- 

 ing table, in wliicli the first column is the date, the second the 

 polar stars, the third the elongations, the fourtli the micrometer 

 value with the first assumption, and the fifth the same with the 

 second assumption. 



Table II. 



1 Western elongation was observed in the eastern position of the telescope and eastern 

 elongation in the western position. 



