392 



SCIENTIFIC RECORD FOR 1885. 



Diameters of the sun and moon as observed with the Greenwich transit 

 circle (W. G. Thackery).— The author considers the values of the diam- 

 eters of the suu and moon furnished each year by the result of all the 

 observations, and also the values resulting each year from the work of 

 the individual observers. The following results were found for the sun, 

 with which are given the results obtained by Sir G. B. Airy, in a paper 

 entitled "On the Circularity of the Sun" {Monthly Notices, vol. xxii): 



The difference in the values of the horizontal diameter is rather sur- 

 prising when compared to the identity of the values of the vertical di- 

 ameter; but the personal equation must be taken into account in con- 

 sidering the observations, the following table showing its importance : 



Tabular errors of the sun's vertical diameter, according to different observers. 



Observer. 



Tabular 

 error. 



No. of 

 obsns. 



Dunkin 



Ellis 



J. Carpenter 



Criswick 



Lynn 



Downing ... 

 Thackeray . . 



Lewis 



Hollis 



+2-28 

 —0-19 

 +3-13 

 +1-65 

 —1-59 

 +1-70 

 -4-1-01 

 4-0-48 

 -fO-15 



138 

 269 

 191 

 347 

 149 

 203 

 141 

 72 

 44 



The observations extend from 1861 to 1883. The error as found by 

 one observer often varies with the time. As to the horizontal diameter 

 found by the transits of the two limbs, the following results have been 

 given by Mr. Dunkin in Vol. xxxv of the Monthly Notices, p. 91, for 

 the period 1864 to 1873: 



Tabular errors of the horizontal diameter. 



Observer, 



Dunkin 



Ellis 



Criswick 



Lynn 



J. Carpenter 



Tabular 

 error. 



-f0.«7 

 +1.48 

 +0.31 

 +1.05 

 +2.45 



