186 



Remarks on tJie Dudley Observatory 



With the help of the equations previously given, each 

 observed time of contact is reduced to the centre of the 

 earth, and in the separate tables of each contact, arranged 

 in the order of time. The first column gives the name of 

 the observer ; the second column the reduction to the 

 center of the earth ; the third the reduced Washington 

 time of contact. The observed local times are not given, 

 but they may be deduced by subtracting the respective 

 longitudes from the sums of the corresponding numbers 

 in the second and third columns of the tables of 

 contacts.* The fourth column of each table gives the 

 correction to prediction, as computed from Leverrier's old 

 theory of Mercury and the other elements of the Ame- 

 rican Ephemeris in the manner already indicated. The 

 fifth column gives the correction to the time predicted 

 from Leverrier's later tables with Leverrier's diameter of 

 the sun. This part of the comparison is derived from 

 " ITature " of June 6, 1878. Though whole seconds only 

 are given here, in the computations the tenths of seconds 

 were always preserved. 



In the first contact the planet was not identified by many 

 observers until the segment was seen to have obtained a 

 very appreciable size. Such observations are not included 

 in the list. 



I. Ingress. External Contact. 



Obaervers. 



Reduction. 



Wn. time, red. 

 to Center of Earth. 



Correction to 

 Am. Eph. 



Brit. N. A. 



Langley, — 2^ 



Doolittle, — 6 



Nav. Acad., — 3 



Landreth, — 11 



221' 04"' 43s 



47 



47 



48 



— 51s 



— 47 



— 47 



— 47 



— 10" 



— 6 



— 6 



— 6 



* Several of the contact times as communicated to me, were given in 

 Washington mean time. 



