468 The Eev. H. Llotd on the Meteorology of Ireland. 



that these facts are by uo means decisive in disproving rotatory movement ; for 

 they are consistent with a rotation of the wind in a plane perpendicular, or 

 highly inclined, to the horizon. Still we are perliaps not justified in assuming 

 the existence of a rotation of this kind, without further evidence ; and it seems 

 more reasonable, in the present state of our knowledge, to admit two different 

 kinds of winds, than to endeavour to reduce all to one by the lielp of a gra- 

 tuitous hypothesis. 



Hourly Observations. — It has been already stated, that hourly observations 

 were appointed to be made during twenty-four consecutive hours, at the equi- 

 noxes and solstices, in the hope that their results might throw light upon the 

 simultaneous atmospheric changes occurring over the island, and especially 

 upon the direction and rate of progress of atmospheric waves. The observa- 

 tions on the first two of these term-days (March 21 and June 21) at six of the 

 stations, are given in detail at the end of this Paper (Table xxxiv.). Those of 

 the two latter (September 22 and December 22) have been omitted, no atmo- 

 spheric change of a marked kind having occurred during them. 



March 21. — A gale occurred on this day, accompanied by a marked baro- 

 metric depression. The minimum of pressure took place during the obser- 

 vations, the time of its occurrence varying considerably at tlie different stations. 

 At Cahirciveen, there was a sudden fall of the barometer between 9 a. m. and 

 10 A.M. followed by a sudden rise between 12 and 1 p.m., the mercury being 

 nearly stationary from 10 a.m. to 12. A similar change took place at Dun- 

 more East, and at the same hours. For these two stations, accordingly, the 

 epoch of minimum pressure may be taken to be 11 a.m. ; the subsequent changes 

 were small and irregular. At Courtown, the barometer descended very slowly 

 and gradually until 5 p.m. ; it then ascended until 10 p.m., after which it de- 

 scended again. All the changes were, however, very small. 



At the northern stations the fall of the barometer was more considerable, 

 and more regular. At Markree, where it was most rapid, it amounted to 0-210 

 in 6 hours. The minimum at Markree occurred between 3 p. m. and 4 p. m. ; 

 at Armagh, the minimum took place at 6 p. m. ; and at Portrush, at 8 p. m. 



From these results it would appear that the trough of the wave travelled 

 from south to north, nearly, with a velocity of about 22 miles per hour. The 

 barometric depression was greatest at Markree, where the barometer stood at 



