ON THE METEOROLOGY OF IRELAND. 375 



all be reduced to their mean values, by multiplying by the factor 

 which expresses the relation of the rain of 1851 to the mean at 

 any one station. We already possess two such mean values : viz., 

 at Armagh and Dublin. They are 29'14 and 34'68 inches re- 

 spectively ; and the factors thence deduced are T10 and 1'05. 



When we examine the results of the preceding Table, taken in 

 connexion with the geographical position and physical circum- 

 stances of the stations, we arrive at the following conclusions : 



1. The places of least rain are either inland, or on the eastern 

 coast ; while those of greatest rain are at, or near, the western 

 coast. Thus the stations at which the yearly fall of rain exceeds 

 40 inches are all on the western and south-western coasts ; while 

 those at which it is below 30 inches are either inland or on the 

 eastern. 



2. The amount of rain is greatly dependent on the proximity 

 of a mountain chain or group, being always considerable in such 

 neighbourhood, unless the station be to the east or north-east of 

 the same. Thus, of the places of least rain, Portarlington lies to 

 the north-east of Slieve-bloom ; Killough, to the north-east of the 

 Mourne range ; Dublin, to the north-east of the Dublin and 

 Wicklow range ; while, on the other hand, the places of greatest 

 rain Cahirciveen, Westport, and Castletownsend are in the 

 vicinity of high mountains, but on a different side. 



These facts are easily explained. The prevailing wind blows 

 from the S. W., and reaches this island loaded with the vapour of 

 the Grulf-Stream. This vapour is condensed and precipitated in 

 rain, when it first meets the colder air over the land, namely, on 

 the western and south-western shores. But the principal con- 

 densing centres are the mountains, in the neighbourhood of which, 

 consequently, the precipitation is more abundant, especially on 

 their western and south-western sides. And the same circumstance 

 which causes the greater precipitation at these points must al> 

 protect the region over which the wind next passes (the north-east), 

 the air being thus deprived of a large portion of its vapour before 

 arriving there. 



NOTE A few of the latter Tables of this Paper, aa originally printed, hare been 

 omitted here as unnecessary. 



