392 



SCIENTIFIC RECOKD FOR 1885. 



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

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

 eters of the sun 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 iu the values of the horizontal diameter is rather sur- 

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

 ameter ; but the i^ersonal 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. 



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 horisontal diameter. 



Observer. 



Dunkin 



Ellis 



Criswick ... 



Lynn 



J. Carpenter 



Tabular 

 error. 



+0.H7 

 +1.48 

 4-0. 31 

 +1.05 

 +2. 45 



