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 difference 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 7 1 on the night of the 1 0th. These two shooting stars gave 

 difference of longitude respectively = 9™ 205-9 and 9™ 19^-9; 

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

 me in the amount P-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 



