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British Association at Edinburgh, and reviewing the history of 

 the principal operations of the kind which have been hitherto 

 performed, the author remarks that the Observatory of 

 Armagh is unfavorably situated for comparison by signals 

 with that of Dublin, though the distance is but sixty-eight 

 miles ; there being ground about four miles to the south of 

 Armagh from 700 to 1200 feet of height; and a ridge from 

 600 to 400 feet high, about fourteen miles north of Dublin. 

 Lieutenant Larcom investigated all possible stations, giving 

 for each its distance aud azimuth, and the height above its 

 summit to which the signal should be elevated to make it 

 visible from both observatories. His help was of essential 

 importance ; and in consequence of the data supplied by 

 him, the station Slieve Gullion was adopted; which is 1893 

 feet high, and is distant eighteen miles from Armagh and 

 fifty-one from Dublin. At the latter its summit is a few 

 seconds above the boundary of view, but, at the former, so 

 much below that boundary, that a height of 800 feet above 

 the summit would be required to clear it. Rockets were 

 therefore necessary, and on applying for them to the 

 Honourable Board of Ordnance, they were supplied from 

 Woolwich with the utmost liberality. 



In the operations alluded to above, the rockets (supplied 

 by the French Goverment) were what is called 2lbs. and 

 carried 8 oz. of powder ; a very great number of them did 

 not rise to a sufficient height ; and Dr. Robinson thought it 

 unsafe to use any of less dimensions. 



The Ordnance also provided tents for the firing party 

 and an escort of police was granted by Lieut.-Colonel 

 M'Gregor for their protection, which however proved quite 

 unnecessary. 



On the 13th of May they were dispatched to the mountain, 

 under the orders of Dr. Robinson's eldest son, and established 

 there in a few hours by the kind aid of the Rev. Dr. Camp- 

 bell, Rector of Forkhill, which removed every difficulty ; and 



