ON THE METEOROLOGY OF IRELAND. 373 



HUMIDITY OF THE AIR. 



The first two of the Tables which follow give the results of 

 the psychrometrical observations. The first contains the monthly 

 means of the tension of vapour at the several stations, calculated by 

 iiegnault's Table ; and the second the corresponding values of the 

 relative humidity, the state of saturation being represented by 100. 



Very few results of a general nature can be drawn from these 

 observations, the distribution of vapour being governed by the 

 proximity of the station to the sea, or by other local circumstances. 

 It will be seen, from the last column of the first Table, that the 

 yearly mean tension of vapour increases, although not in any 

 regular progression, in proceeding from the north to the south of 

 the island. Its mean value for the entire island is 0*326 of an 

 inch ; its greatest value (at Westport) is 0'374. 



The distribution of humidity is still more under the influence of 

 local circumstances, and therefore still less regular. Thus, Portrush 

 and Castletownsend the one at the northern, the other at the 

 southern extremity of the island have nearly the same mean 

 humidity ; while Portarlington and Athy places near each other, 

 and both inland are almost at the opposite extremities of the 

 .scale. The driest station is Portarlington; the most humid. 

 Westport. At the latter place, in fact, the air is nearly saturated 

 with moisture, the place of observation being entirely surrounded 

 by water, and but a few feet above the sea. The mean humidity 

 for the entire island, for the year 1851, is 87. 



EAIN. 



Before proceeding to the observations of rain-fall throughout 

 Ireland in the year 1851, it is important that we should know its 

 normal amount at one or more stations, as deduced from the mean 

 of several years. We have, for this purpose, two series of obser- 

 vations, one at Dublin, and the other at Armagh, extending 

 uninterruptedly over eleven and twelve years respectively. The 

 results of these two series are contained in the third and fourth of 

 the following Tables. 



The lowest line in each gives the mean monthly fall of rain. 

 It will be seen, from an inspection of the numbers, that there is 



