120 The Rev. Dr. Robinson on the Longitude of the Armagh Observatory. 



The geodetic diflFerence of longitudes is, as I have already said, altogether 

 unconnected with this inquiry, but in the ensuing summer I hope that we shall 

 be able to lay before the Academy a determination of the differences between 

 Dublin and Armagh, by means of Rocket signals, for which the Honourable 

 Board of Ordnance have afforded us most ample means, though unfortunately 

 too late in the autumn to be available this year. By the valuable aid of Lieute- 

 nant Larcom, I trust we shall be enabled to perform this interesting operation in 

 the most satisfactory way ; and by extending the same system to Mr. Cooper's 

 Observatory at Markree, we shall have an arc of longitude measured in the most 

 perfect manner, entirely across the island. 



Armagh Observatory, 

 J\rov. 9, 1838. 



