8 



tude, was introduced by me for the purpose of facilitating the 

 identification of the objects seen at both the stations. This 

 was necessarily a rough approximation, obtained as follows : 



" The longitude of Dunsink, according to the Nautical 

 Almanac, = 25" 22' W. of Greenwich ; and that of Markree 

 Observatory, =33'" 48^-4 W. Thus the difference of longi- 

 tude between Dunsink and Markree = 8™ 26*-4, Applying a 

 scale to the Ordnance Sketch Map of the county of Dublin, 

 the Obelisk at Killiney appeared to be nearly 9*55 statute 

 miles to the eastward of Dunsink ; and then, assuming a degree 

 of longitude in latitude 53° 15' to equal about 41-45 statute 

 miles, a simple rule of three gave the difi'erence of longitude 

 in time between Dunsink and Killiney = 55'3. This being 

 added to 8™ 26''4, the difference between Dunsink and Mark- 

 ree, produced the result, — difference of longitude between 

 Markree Observatory and the Obelisk at Killiney = 9"" 2P'7. 

 With this result I estimated the times at Markree correspon- 

 ding to the times at Killiney. 



" Upon my sending my observations on the 10th and 12th to 

 Mr. Graham, he identified my Nos. 30 and 38 with his Nos. 13 

 and 71 on the night of the 10th. These two shooting stars gave 

 difference of longitude respectively = 9™ 20*"9 and9"19'"9; 

 the mean, 9"" 20^-4, differing from the longitude assumed by 

 me in the amount l'-3. But I subsequently discovered that 

 the shooting stars. No. 8 Markree, and No. 27 Killiney, on 

 the night of the 12th, were one and the same, giving, for 

 difference of longitude, 9™ 23^-4. The mean of the three 

 is 9™ 21^-4, which differs only 0^-3 from that which I had 

 estimated. 



" That the result is in reality as satisfactory as it appears to 

 be, I cannot assert. Fractions of seconds in the observations 

 could scarcely have been attended to under the circumstances, 

 and therefore were neglected ; those appearing in the lists, 

 arising from the application of the corrections for clock at 



