Lyons — The Distribution of Mean Annual Rainfall. 369 



■with the very narrow area of the zone under 28 inclies, is an important 

 feature of the present distribution. From Terenure, with a mean of 27*5 

 inches, to Glenasmole Lodge, with a mean of 53-0 inches, the distance is 

 only a little over six miles. A very remarkable difference is also found 

 between the rainfall at Grlenasmole Lodge and Grlenasmole Waterworks, 

 within a distance of two miles. Tlie record at the former is uniformly and 

 considerably liigher than at the latter. The annual rainfall graphs run 

 practically parallel, but tlie mean of the Lodge record is 53, and that for 

 the Waterworks is 45 inches. The gauge at the Lodge was unfortunately 

 abandoned in 1889, owing to the site being affected by trees. The caretaker, 

 Mr. O'Brien, who gives the closest personal attention to the rainfall and 

 general weather of the district, finds both the frequency of showers and the 

 intensity of rain greater at the Lodge than at the Waterworks. He tells 

 of having frequently experienced very heavy rain at the former place during 

 a day when the gauge at the Waterworks registered but a small amount ; 

 and the sudden rise of the river flowing from the Lodge has often indicated 

 heavy and continuous rain at the upper valley when that registered at the 

 Waterworks was insignificant. 



The increased precipitation at Glasnevin compared with the city is very 

 interesting and difiicult to explain, especially when we conSi<ler the low 

 rainfall of the coast districts to the north. The exceptionally low value for 

 Lambay Island is perhaps to be connected with the small rainfall usually 

 observed near the sea ; but the data for Lambay are too restricted to merit 

 discussion at present. Passing from the lower limit to the higher limit of 

 the rainfall, we find a considerable amount of interest in the record for 

 Laragh (Grlendalough). The station is situated at a comparatively low level 

 in the midst of the mountains, and to tlie north-east of Lugnaquilla (;3039 

 feet). Its moan annual rainfall works out at 59 inches. 



In considering this record of Grlendalough attention must be paid to the 

 fact that on mountains a definite maximum zone of rainfall occurs ; and this 

 maximum is found sometimes on the summit, sometimes on the windward, 

 and occasionally on the leeward side. In the Lake District' the maximum 

 occurs at an altitude of about 1500 feet ; and the striking fact is tliere noticed 

 that the rainfall at 3000 feet is about 90 inches, whereas in the valley on the 

 lee side the rainfall is about 140 inches. The Lake District being exposed to 

 the practically direct approach of the rain-bearing winds from the sea is 

 probably subject to more exceptional conditions than Wicklow. It is never- 

 theless possible that the rainfall of Glendalough is not much lower than the 



' " British Rainfall," 189V. 

 SCIENT. PKOO. R.D.S., VOL. SII., NO. XXX. 3 O 



