between the Observatories of Armagh and Dublin. 145 



position of another point, likely to become of great importance, the Observatory 

 of E. J. Cooper, Esq., at Markree ; which, not merely from the magnificence of 

 its instruments, but the intention of its possessor to make it a permanent estab- 

 lishment, merits this distinction. It will be seen, on referring to the map, that 

 the high mountain Cultiagh, in Leitrim, has been selected with this view : it is 

 visible from Markree, barely hid from Armagh by Cairnmore ; and, though 

 eighty-two miles from Dublin, yet, as 1700 feet above its summit will reach the 

 view at that place, this, also, is completely within the scope of these rockets. 

 If there be any fine weather in autumn, I hope to perform this then ; and, 

 afterwards it will be our object to connect the Irish observatories with those of 

 Scotland and England. Several points in Antrim are visible from Armagh, 

 and also from the west coast of Scotland : and if the method of successive signals 

 were employed, there is no difficulty in reaching Edinburgh. But for reasons 

 already given, I would use this only as a last resource, and then make the inter- 

 mediate stations absolute, which, if they are chosen at primary points of the tri- 

 angulation, is likely to give very useful geodetic information. 



But in the present instance I conceive it quite possible, by using large 

 rockets, to effect the junction with one signal station. The mountain Goatfell, 

 in the Island of Arran, has been chosen as the station. Its height is 2865 feet, 

 and if the rockets can add to this 3300, they will be in view both here and at 

 Edinburgh, the distances being 105 and 86 miles. 



That this can be accomplished is certain, for a few which I made recently, no 

 heavier than those which have been described, rose, with four ounces of powder, 

 4.500 feet ; and if the Board of Ordnance continue their powerful aid to us, I am 

 confident of success.* 



Similar rockets will, I think, also connect immediately Oxford with Dublin. 

 If fired on Plinlimmon, 1500 feet will bring them within view of the latter, and 

 also of the other, probably, unless the circumstances of the ground in its vicinity 

 forbid it. But as to this I have not yet consulted my geodetic Mentor. If, 

 however, it be necessary to observe them from one of the neighbouring hills, 



* Since this was written, the Board have granted my application for a supply of rockets capable 

 of ascending to the required height. 



VOL. XIX. U 



