Clare Island Survey — Climatology. 6 17 



reasonable to conclude, however, that the rainfall at the Abbey is highest, 

 and that at the lighthouse lowest ; and that the low-lying district near the 

 hotel is representative of the mean for the whole island. Those results are 

 in accordance with the known effects on rainfall of exposure to wind and of 

 configuration. 



The average number of rain-days per annum for Blacksod is the highest 

 quoted in the Appendix to the Weekly Weather Eeport, 1906, out of 

 119 stations in the British Isles. Clare Island, Westport, and district would 

 appear to approximate to, if not actually to be in excess of, Blacksod in the 

 frequency of rain. As regards amount of rainfall, however, Clare Island is 

 probably below Blacksod. The rainfall over the sea is generally supposed to 

 be less than over the land : and the well-known effect of mountains on 

 rainfall would not generally appear over Clare Island. It is, however, marked 

 in the returns from Dugort and Crossmolina. 



The monthly variation and general conditions as regards means and 

 extremes of rainfall will be best studied by reference to the numbers for 

 Blacksod Point contained in Table XI. 



The most striking feature of the above table is the second part referring 

 to the frequency of rain in this district. The very high annual average of 266 

 is found to accompany the high average for practically every month. The 

 driest months, May and June, on an average have more wet than dry days ; and 

 in the case of the wet months, December and January, we find the average 

 number of wet days in each to be twenty-six. The highest values include 

 several instances where every day in the month had a record of rain, and in 

 the case of the year 1898 only on sixty days did no rain fall. The frequency 

 of rain in this area is, however, perhaps, best emphasized in the numbers giving 

 the lowest number of rain-days recorded in the twenty-five years from 1886 

 to 1910. January, March, October, and December never show less than half 

 of the days with some rain, and the lowest number of rain-days for a year is 

 213 in 1896. A comparison of Blacksod and Valencia shows a parallel 

 variation from month to month as regards annual rainfall and average 

 number of rain-days. But, whereas the Valencia rainfall is for every month 

 higher than that of Blacksod, the number of rain-days for the latter is always 

 greater except in June and September, when they are equal. 



The mean monthly variation during the year for Blacksod may be regarded 

 as typical for the whole district, and presents the following points of interest. 

 The autumn and winter months show a much higher rainfall than the spring 

 and summer months of April, May, June, and July. December and January 

 show the heaviest rainfall. This is in marked contrast with the mean monthly 

 variation in Dublin, where the months of December, January, February, 



K.I. A. PROC, VOL. XXXI. C 6 



