of the Sun's Disc. 



536 



being still 32' 1"«80. From 1853 to 1860 the telescope of the 

 Transit-Circle was used for both measures^ but the Nautical 

 Almanac assumed diameter was 32' 3"'64. 



Apparent Errors of the Duration of Passage of the Sun's Hori- 

 zontal Diameter, and of the Sun's Vertical Diameter, as com- 

 puted in the Nautical Almanac. . ; 





No. of obs. of 



Mean value of 



No. of obs. 



Mean value of 



Year. 



horizontal 

 diameter. 



N.-A. Ob* 



of vertical 

 diameter. 



N.-A. Ob. 



1836. 



104 



-017 



116 



^1-50 



1837. 



92 



-0-18 



122 



-1-85 



1838. 



108 



-014 



115 



-1-53 



1839. 



103 



-0-14 



114 



-0-94 



1840. 



104 



-018 



112 



-1-60 



1841. 



102 



-014 



109 



-1-32 



1842. 



116 



-0-14 



121 



-1-54 



1843. 



99 



-014 



107 



-1-84 



1844. 



102 



-0-18 



117 



-1-50 



1845. 



100 



-017 



113 



-1-32 



1846. 



92 



-0)0 



101 



-209 



1847. 



89 



-0-05 



89 



-2-98 



1848. 



94 



-0 06 



102 



-206 



1849. 



103 



-011 



101 



-2-40 



1850. 



94 



-011 



86 



-218 



1851. 



87 



-008 



106 



-0-71 



1852. 



103 



-012 



112 



-1-39 



1853. 



78 



000 



86 



+0-58 



1854. 



109 



+009 



111 



+ 1-29 



1855. 



84 



+0-07 



93 



+065 



1856. 



104 



+0-10 



109 



+ 1-17 



1857. 



113 



+007 



123 



+0-99 



1858. 



126 



+0-07 



132 



+0-92 



1859. 



109 



+008 



125 



+0-99 



1860. 



72 



+009 



72 



+1-64 



If we take the sums of the numbers of observations and the 

 means of the errors, and if we remark that the mean error of the 

 horizontal diameter in arc may be obtained from the mean error 

 of the duration of passage without sensible error by multiplying 

 by 14, we obtain the following numbers : — ■ 



Period. 



No. of obs. 



Mean en-or 

 of N.-A. 



duration of 

 passage. 



Blean error 

 of N.-A. 

 horizontal 

 diameter. 



No. of obs. 



Mean error 

 of N.-A. 

 vertical 



diameter. 



1836 to 1850. 

 1851 and 1352. 

 1853 to 1860. 



1502 

 190 

 795 



-0-134 

 -0-100 

 +0-071 



-1-88 

 -1-40 

 +0-99 



1625 

 218 

 851 



-'i-78 

 -105 

 +1-03 



* If we change the signs of these errors to form corrections, and 



