34 



quently, that it deviated from a circular form ; but the gra- 

 dually diminished force of the gale in the latter portion renders 

 it impossible to fix its close with precision. The total diame- 

 ter, in the direction of the progressive movement, probably 

 exceeded 500 miles. The magnitude of the (nearly) quiescent 

 portion of ah in the centre of the vortex is better defined. At 

 Armagh the lull lasted from three to four hours ; at Markree 

 three hours ; and at Donaghadee four hours. The diameter 

 of the quiescent central portion was therefore about 50 

 miles. 



"I shall now refer to some particulars connected with this 

 gale, which appear to merit attention — although probably, in 

 the present state of knowledge on this subject, we should not 

 be justified in offering any suggestions in explanation. 



"Among the first of these are the abnormal irregularities 

 in the rotatory movement, especially along the track of the 

 centre. Thus we have seen that, at Markree, there was a 

 subsidence of the gale from 7 p.m. to 10 p.m. of the 18th. 

 There was, in like manner, a temporary lull at Armagh, be- 

 tween 3 and 4 a. m. of the 19th. But the most curious irre- 

 gularity is that of the direction. At Armagh this began to 

 change rapidly at 9 p. m. of the 18th. At 9 p. m. it was 

 E.S.E. ; at 10 p. m., S. E. ; at midnight, S.S.E.; and at 



I a. m. on the 19th, S. At this point it remained for several 

 hours ; and the direction then retrograded through an arc of 

 about 45°. At 9 a. m. on the 19th, it was S.S.E. ; and at 



I I a. m. it came back to S.E., after which the sudden shift to 

 W. N. W. already noticed, took place. 



" The next point which seems to merit notice is the fact, 

 that the force of the gale was considerably greater to the south 

 of the line of passage of its centre, than on that line itself, or 

 to the north of it. Thus, at Killiney, where I made frequent 

 observations during the gale, I found the maximum velocity 

 to be 55 miles an hour ; at Armagh it was but 30 miles. It 

 would be easy to account for this, if we could suppose that 



