492 Trans. Acad. Sci. of St. Louis. 
Professor Ficklin’s results for micrometer revolution are as 
follows :— 
Mean value of 1 revolution = 46”.63 + 0.05. 
These values of the instrumental constants agree fairly 
well with the values adopted by the Coast Survey in 1874. 
They were used by Prof. Ficklin in reducing the observations 
and are adopted in the reduction which follows. While the 
observations were being made the instrument was mounted 
in the transit room — probably on the central pier. 
Re-reduction of the Observations. The values of the 
instrumental constants adopted in this reduction are: 
1 Micrometer Revolution = 46”.63--0".05 
1 Division of Level = 1”.25 
The average value of the micrometer correction is — 1.9 
revolutions, so that an error in the adopted value of 1 revolution 
of the micrometer screw will affect the latitude by almost twice 
its full amount. But the previous determinations of the 
Coast Survey observers indieate that the adopted value is as 
near the truth as the probable error would indicate. 
The pairs of stars observed by Prof. Ficklin are given in 
Table I. The error in choosing the stars of the eighteenth 
pair is due to a mistake of 9 degrees in the declination of 
