33 
<< At Markree the gale commenced at 4" 30™ p. m. of the 
18th, with a rapidly falling barometer. At 7 P.M. the wind 
abated to a breeze, the barometer still falling. It recommenced 
at 10 p.m. from the S. E.; and at 3 a.m. on the 19th it appears 
to have attained its maximum. At 6 a.m. the wind again 
abated; and at 7 a.M. there was a calm. The minimum pres- 
sure took place at this time, and amounted to 28-058 inches. 
At 9 a.m. the wind rose again from the N.N.W., but not 
with such force as before; and in the afternoon there was a 
strong gale again. 
‘** From these facts it is evident that the centre of the vor- 
tex passed nearly over Markree at 7 a. M., and over Armagh at 
11* 30" a.m. At Donaghadee, which is nearly in the prolonga- 
tion of the line connecting the two former places, the wind 
ceased at 1 p. m., and recommenced at 5 p.m.; so that the 
vortex passed nearly centrally over this station at about 3 p.m. 
From these data we learn that the cyclone movedfrom W.S.W. 
to E.N.E.; and that the velocity of the progressive move- 
ment was about 14 miles an hour.* ) 
“¢ The dimensions of the vortex may likewise be collected 
from the same data. ‘The interval between the commence- 
ment of the storm, and the passage of the centre, at Armagh, 
was 16} hours; and, the velocity being 14 miles an hour, the 
distance between the front of the vortex and the centre was 
230 miles. We have grounds for believing that the posterior 
portion of the vortex was more considerable, and, conse- 
* «<The direction of the progressive movement may also be inferred, 
although not so satisfactorily, from the initial and final directions of the 
wind, in veering, at any one station. And, the time of the nearest approach 
of the centre of the vortex being that of least pressure, the rate of the pro- 
gressive movement may be ascertained by a comparison of the heights of the 
barometer at two distant stations, the direction being known. Thus, the 
time of the minimum pressure at Caherciveen (deduced by interpolation) 
was about 3 a.m., and that at Donaghadee about 3 p.m.; which gives a 
velocity of 18 miles an hour.” 
; VOL. V. D 
