356 ON THE METEOROLOGY OF IRELAND. 



to, not far from Donaghadee. Least pressure at Donaghadee, as 

 before. 



Oct. 23, 9 P. M. Rotatory movement continued. Centre of 

 vortex had moved from S.W. to N.E., at the rate of about 100 

 miles per diem. Absolute minimum of pressure (=29 -3 60) at Donagh- 

 adee; increase of pressure in 100 miles = O'lO inch. 



Nov. 18, 19. A cyclone, with violent storm, crossing the island 

 from W. S.W. to E.N.E. (Plate III., figs. 1,2,3.) The movement 

 of the centre of the vortex appears to have been curvilinear, and to 

 have varied considerably in velocity. Between 9 p. M. of the 18th, 

 and 9 A.M. of the following day, its path was from S. W. to N. E., 

 and its velocity about 320 miles per diem ; in the succeeding twelve 

 hours its course was nearly from W. to E., with a greatly diminished 

 velocity. The mean velocity of the wind, throughout the storm, 

 was from 45 to 50 feet per second. 



Nov. 18, 9 P. M. Centre of the vortex on the south-western 

 coast, about 30 miles to the north of Cahirciveen. Least pressure 

 at Kilrush. Maximum velocity of wind (in south of island) = 60 

 feet per second. 



Nov. 19, 9 A.M. At this epoch the wind was blowing from N. 

 at Killybegs, and from S. at Donaghadee ; it was blowing from 

 S. E. at Portrush, and from N. W. at Castletownsend ; from 

 S. S. E. at Armagh, and from N. N. W. at Markree. The centre 

 of the vortex was therefore over Ireland at that time, and between 

 the stations above mentioned, its exact position being about 15 

 miles to the west of Armagh. Absolute minimum of pressure 

 (= 28*248) at Armagh ; increase of pressure = 0'31 inch. Maximum 

 velocity of wind (in south) = 65 feet per second. 



Nov. 19, 9 p. M. Centre over the Channel, to the south-east of 

 Donaghadee. Absolute minimum of pressure (= 28*410) at Donagh- 

 adee ; increase of pressure = 0-28 inch. Maximum velocity of wind 

 (in south) = 55 feet per second. 



We have seen that the centre of the vortex was between Armagh 

 and Markree at 9 A.M. of the 19th ; and, as the direction of its 

 progressive movement was not far from the line connecting these 

 places, it must have passed nearly centrally over both. Hence we 

 should expect there the peculiar phenomena the Ml of the wind, 

 and the sudden reversal of its direction which are observed to 

 occur at places in the path of the centre of a cyclone. I shall, 



