114 The Rev. Dr. Robinson on theLongitude of the Armagh Observatory. 



rfL" = |-e + ie' 



Errors caused by the journey produce opposite effects going and returning, and 

 as the disturbances may be expected to be nearly equal in the two cases, it is 

 highly probable that their effect on the mean longitude is insensible in such a 

 case as the present. 



Having premised so much as to the principles of the process, I annex its 

 elements. The first column of the following table contains the number and dis- 

 tinguishing letter of the watch ; the second its correction at the epoch of its own 

 time given in the third ; the fourth and fifth are for the return. 



GREENWICH OBSERVATORY. 



GREENWICH NAVAL SCHOOL, REDUCED TO THE OBSERVATORY. 



