42 



THE CLIMATE OE IRELAND. 



From observations on evaporation during two consecutive years, Mr. 

 James Price, C.E., found that at Dublin and Galway it 

 amounted to 26 inches ; while at Cavan, where the 

 soils are retentive, and in the vicinity of which sheets 

 of water and tracts of peat abound, the evaporation 

 These circumstances are referred to by Sir J. William 

 Moore,* who further points out that though the rainfall at Galway is greater 

 than at Cavan, the habitual comparative dryness of the former, and of Clare, 

 renders their local climate preferable to that of Cavan, being more bracing. 



On page 354 of his work.t Sir J. W. Moore gives a Table setting forth the 

 results of observations from 1865 to 1887, upon the temperature, humidity, 

 cloudiness, rainfall, etc., at Dublin, a portion of which is here borrowed : — 



Yapour 

 Condensation. 



was only 13 inches. 



At night, when the air cools down — through contact with the earth, itself 

 cooled by radiation — a temperature is reached at which the air can no longer 

 retain its vapour in invisible form (for the warmer air is, the greater is its 

 capacity for vapour) ; the vapour then condenses, and becomes visible as fog, 

 which rests on vegetation and soil as dew, or in extreme cases of cooling as 

 hoar frost. The temperature at which fog begins to form is called the dezo 

 point, also given in Meteorological Tables. At the dew point the condensa- 

 tion of vapour causes a release of latent heat, which tends to preserve the 

 layer of air in contact with vegetation from extreme cooling — an important 

 consideration in early spring. We may say then that the higher the dew 

 point is, the less likelihood there is of injury from frost. These circum- 

 stances exhibit the bearing of meteorological data upon the prospects of 

 Irish farming. 



Happily the lowland parts of Ireland are not so cold as commonly to 

 produce vapour condensation, except at night ; 

 but this often takes place during the day around 

 the colder mountain-tops and along the flanks of 

 hills, and affords a familiar index of humidity, and 

 forewarning of probable mist and rain. The 

 liang about such situations, have a baneful influence upon 



Fog, Cloud, Mist, 

 Bain. 



fogs which 



* " Meteoroloj,'y, Practical and Applied," pp. 184, 1S5. t Op. cit., pp. 184, 1S5. 



