144 The Rev. Dr. Robinson on the Difference of Longitude 



With 71 Aqullae, 8 = _ 1° 40' by 16 pairs, 



E' - Ts = 24s 2871 „ _ , 0' 147 

 t' - e' =24 581/^ - +0.147 



25 Aquarii, 8 = -|" 1° 31 by 17 pairs, with another opening of the wires, 



E — T = 20' 0881 , „ ,^^ 



T' - E' = 20 412) ^ = + 0-162 



Another set of 14 pairs, 



E — T = 20» 053\ „ ^n^KA 

 T'-E'=20 37l|'^ = + °-^^* 



63 Aquarii, 8 = — 5° 6', 16 pairs, 



E— T = 20»100\„ im^o 

 T'-E' = 20 444) ^ = + 0-1^2 



Again 15 pairs, 



E — T = 20' 207) , n ono 



T'-E'= 20 613} ^ = + 0-203 



The mean of the seventy-eight pairs is -\- 0'.167, or Mr. Thompson observes 

 so much later than Mr. Edmondson. I regret that the moon was not observable. 

 They tried the sun's second limb, and found by 14 pairs p = + 0.225. 



Hence, our true difference of longitude is by 



Rocket signals . 1". 14'. 258 

 Chronometers . . 14 220 



I stated that it appeared unnecessary to continue the signals at Slieve 

 Gullion ; and this, I hope, will be admitted in reference to the object proposed, 

 the determination of the arc of longitude between Dublin and Armagh. 



As, however, calculating on the number of failures in the French rockets, I 

 had got more than proved to be required, it is my intention to employ the re- 

 mainder in a way, which, while it verifies the present work, will determine the 



