304 



THE SAYRE OBSERVATORY. 



These values are brought together for convenience of reference, in connection with 



the weighted mean date of the determination. 





Weighted 





No. Obs. 





Weighted 



Latitude 



No. Obs. 





Mean Date 









Mean Date 







1 



1870.285 



40 30 23. 05 



56 



12 



1888.702 



40 30 23.09 



121 



2 



76.607 



23.56 



81 



13 



89 980 



23.10 



22 



3 



77.287 



2)!. 90 



01 



14 



90.137 



23.31 



15 



4 



77.420 



23.72 



21 



15 



90.269 



23.52 



88 



5 



77.800 



24.24 



70 



10 



90.309 



23.62 



43 



6 



77.763 



24.09 



26 



17 



90.484 



23.57 



78 



7 



78.222 



23-51 



12 



18 



90.554 



23.55 



55 



8 



85.736 



23.72 



115 



19 



90.629 



23.36 



33 



B 



86.301 



23.40 



50 



20 



90.724 



23.55 



19 



10 



86.459 



23.32 



95 



21 



90.818 



23.15 



31 



11 



86.551 



23.80 



22 



22 



90.900 



23.05 



30 



The most noticeable feature of this series is the progressive diminution in the mean 

 value which seems to have taken place, the minimum value in 1876 being apparently 

 nearly the same as the maximum in 1890. 



SECOND S Kill KM. 



December 1, 1889, to December IS, .18,90. 



Before beginning operations on this series the instrument was thoroughly repaired 

 by Saegmiiller, of Washington, and a level was selected from some eight or ten which he 

 had in stock and which were regarded as particularly fine tuhes. As a result the per- 

 formance was greatly improved in every way, as may be seen by reference to the probable 

 errors found on page 302. 



Level Value. 



The level was examined by means of the level-trier five times during the year with 



Number determinations. 

 5 

 

 5 

 4 



One determination consists in moving the bubble over the entire length of the scale, 

 or at least considerably more of it than is actually employed in observation, at intervals 

 of two divisions of the micrometer screw, then moving it in the opposite direction at the 

 same readings of the screw. From one to two minutes' time is allowed after each setting 

 for the bubble to come to a condition of equilibrium. About one hour will usually be 

 employed in this operation. 



the following results : 









Date. 



Value 



one division. 



Thermometer 



1889 November 21-23 





1.24 



46« 



December 19-21 





1.43 



42 



1890 July 14-15 





1.16 



78 



November 11-12 





1.16 



43 



