360 



ON THE METEOKOLOGY OF IRELAND. 



These differences are probably connected with the difference of 

 altitude of the places of observation. 



1851. Jan. 15, 16. A remarkable case of a double cyclone 

 with storm, and a double minimum of pressure. (Plate III., figs. 

 4, 5, 6.) The first of the two vortices crossed the island from S. 

 to N. on the 15th, and the second traversed the north-western 

 portion of it, from S. W. to N. E., on the following day. The 

 velocity of the former is not well determined ; that of the latter was 

 about 270 miles per diem. The mean velocity of the wind was 

 from 30 to 35 feet per second on the former day, and from 55 to 

 60 on the latter.* 



Jan. 15, A. M. Centre of vortex about 20 or 30 miles south of 

 Dunmore. Absolute minimum of pressure (= 28'718) at Dunmore ; 

 increase of pressure = 0-15 inch. Maximum velocity of wind (west 

 coast) = 60 feet per second. 



Jan. 15, 9 p. M. Centre of vortex appears to have been at this 

 time a few miles north of Buncrana ; the cyclonic movement was, 



* The following extra observations were taken at Markree : 



