Clare Island Survey — Climatology. 6 15 



The decrease in humidity in passing from January to May, and the 

 subsequent increase, are in accordance with observations at other stations. 

 The variation from June to December is, however, remarkable for the slow 

 rate of increase. The pronounced drop in humidity in October is most 

 unusual and inexplicable, and seems open to question. It would appear, 

 however, that the Blacksod humidity does not increase as rapidly in passing 

 through autumn to winter as does the humidity of such stations as Valencia 

 and Markree Castle. It is stated that fogs are unusual on the north-west 

 coast of Ireland ; and this might be connected with the lower autumn 

 humidity. 



5. Bain fall. 



For the purpose of studying the rainfall of Clare Island and district 

 reference was made to — 



(a) The manuscript copies of the monthly summaries for Blacksod, which 



were supplied by the Meteorological Office. 



(b) Appendix III to the Weekly Weather Beport, 1906. 



(c) The volumes of " British Bainfall." 



(d) Becords of gauges kept in Clare Island, 1910-1912. 



The monthly summaries contained the mean monthly rainfall and mean 

 number of rain-days per month for Blacksod, based on a twenty-five year 

 period (1886-1910). The Blacksod observations extended only from 1899- 

 1910, but were "weighted" by comparison with the values for Crossmolina 

 and Enniscoe, which were given in "British Bainfall." The highest and 

 lowest values for each month's rainfall, and the corresponding years of 

 occurrence, were also given, as well as similar information for the number of 

 rain-days. (See Table XL) 



In Appendix III to the Weekly Weather Beport, 1906, there are given in 

 Table II the average rainfall and average number of rain-days for each 

 month, and of the whole year, for a large number of stations in the British 

 Isles, including Blacksod, Markree Castle (Co. Sligo), and Valencia. The 

 values are estimated for a thirty-five-year period (1871-1905). * " British 

 Bainfall," 1911, contains the values of the total rainfall for that year at the 

 following important stations : — Blacksod, Westport, Dugort, Crossmolina, 

 Cong, as well as three returns for Clare Island. 



1 In the case of stations with shorter records, e.g. Blacksod Point, the averages were weighted 

 in the usual way, " by comparing the observed fall with that for a corresponding period at a 

 neighbouring station, possessing records for thirty-five years, and assuming that, in the long run, 

 the amounts recorded at the two stations bear a constant percentage relation to one another (see 

 Hann, 'Lehrbuch der Meteorologie,' ed. 1906, p. 24S)." — Extract from notes to Weekly Weather 

 Report, 1906. 



