ON THE METEOROLOGY OF IRELAND. 365 



From the facts above stated, we may draw the following general 

 conclusions : 



1. The occurrence of cyclonic movements in the atmosphere is 

 not infrequent in Ireland, and may be traced even in the case of 

 moderate winds. 



2. The rotatory movement is invariably in the same direction, 

 namely, that opposite to the diurnal movement of the sun in 

 azimuth. 



3. This rotation is always accompanied by a considerable dis- 

 turbance of barometric equilibrium, which is greater in proportion 

 to the velocity of the rotatory movement, the pressure being a mi- 

 nimum at the centre of the vortex, and increasing regularly with 

 the distance from that point. 



4. The place of greatest velocity appears to have no very defi- 

 nite relation to that of the centre of the vortex, sometimes nearly 

 coinciding with it, and at others being situated in front, or in the 

 rear, on the right hand, or on the left, of the centre.* 



5. The vortex itself has a progressive movement, at the rate of 

 from 100 to 300 miles per diem, the average velocity of those 

 observed being 220 miles per diem. The direction of this movement 

 in Ireland is generally from S. W. to N. E. 



6. If a line be drawn through the centre of Ireland, in the 

 direction from S. W. to N. E., the track of the centres of by far 

 the greater number of the cyclones, passing over or near Ireland, 

 lies to the north of that line. 



7. There is reason to conclude, that these rotatory movements 

 are caused by the conflict of two rectilinear currents moving in dif- 

 ferent directions. 



STORMS. 



For the purpose of eliminating local irregularities, and (to a 

 certain extent also) inequalities of estimation, I have, in examining 

 the distribution of the higher winds, combined the stations into 

 four groups, omitting Portrush and Buncrana, which lie somewhat 

 apart. These groups are as follow : 



I. NORTH-EASTERN. Donaghadee, Killough, Armagh. Mean 

 latitude = 54 24'; mean longitude = 5 57'. 



In the remarkable cyclone of November 18, 19, 1850, the wind raged with 

 greatest violence on the right hand of the centre (looking in the direction of the pro- 

 gressive movement) ; and this appears to be the case of most frequent occurrence. 



