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Show 19 '$ The values of m, ? i, and c, used in the redaction, are as Date. | m i *. May 19 - 0.143 May 23 ' - 0.046 Maj' 24 - 0.010 June 16 ' - a 113 n + 0.184 + 0.088 + 0.082 + 0.242 follows : c + 0.108 - 0.114 - 0.110 + 0.030 From the clock- corrections obtained from the observations the following corrections and rates were computed by the method of least squares, and have been employed to determine the error of the clock at the time of the interchange of signals on each night: Date. May 19 Mav 23 Mav 24 Sidereal hour. 14.0 16.0 15.0 17.0 Correction. g. tt. - 0.594 ± 0.007 + 2. « > 4± 0.010 + 2.117± 0.012 - 2.234± 0.007 Hourly rate. - 0.034 - 0.039 + 0.016 - 0.013 UNITED STATES LAKE SUBVEY, DETROIT, MICHIGAN. The dates of the observations are May 19, 23, and 24, and June 1, 3, 10, 16, 26, and 29, 1871. The observer at Detroit was Mr. O. B. Wheeler, assistant United States lake- survey, aud the instruments used were the Troughton and Simtns transit of 43 inches focal length, clock No. 184, Bond & Son, and chronograph No. 216, Bond & Son. The stone pier upon which the transit- instrument was mounted is situated 321.0 feet west and 294.0 feet north of the southwest corner of the stone foundation of the Westminster church, on Washington avenue. The reductions have been made by Messrs. Thomas Russel, O. F. Burton, and John Eisenmann, subassistants United States lake- survey. A preliminary reduction by high and low stars of May 19, 23, and 24, was made by Mr. Burton. Two reductions by the method of least squares, on different suppositions, were made, either of which would cause an extreme range of only 08.05 from the preliminary reduction. For the remaining elates, the high aud low star reductions were made by Mr. Eisenmann, and the least- square reductions by Mr. Russel. The agreement in extreme cases was the same as above. In the following tables are contained the abbreviations: C Ji = reduction to the middle wire; Aberr = diurnal aberalion; B 6 = level- correction; C c == collimationcorrectioii; t' = observed time of transit of a star, commonly the mean of five wires; *^= t the above corrections being made; o = right ascension of a star; ( « - t)-( an assumed J£)= the absolute termof the equations of condition ; a= deviation from the meridian, + when the instrument points east of south; € = distance of the middle wire from the line of collimation ; />= hourly rate of the clock ; M= clock- correction, - when fast; + when slow. |