THE CLiMAi'E Ui" IRELAND. 43 



the agriculture of hilly districts. They hinder the passage of the sun's 

 light and heat, which otherwise would counteract the cooling effects of air 

 descendmg from the hillsides into the valleys, and to the land margining 

 the hills ; with the results of late springs, late and damp harvests and other 

 disadvantages. 



The meeting of currents of air in the higher regions of the atmosphere, 

 one cold and probabh- dr}', the other warm and damp, will, when they coal- 

 esce, if the latter be sufftciently humid, result in the condensation of the 

 contained moisture, which will form cloud and possibly give rain. The 

 currents, too, before meeting may contain sufficient cloud to indicate their 

 directions, and render it possible to forecast the result. 



Sir J. W. Moore, M.D., etc., has given in his work on Meteorology (p. 221),. 

 an excellent classification of clouds, to which attention is here directed. 

 Some accompany fine, and some bad weather. 



Amongst the former are — Cirrus or "mare's tail;" Alto-cumulus; 

 Cumulus or " wool-pack ; " and amongst the latter are Cirro-stratus or 

 "sheet-cloud;" Alto-stratus or "ground fog;" and Cumulo-nimbiis or 

 " rain cloud." The altitudes of clouds range from about g,ooo metres 

 (nearly 10,000 yards in the case of Cirrus) to some 2,000 yards in the case 

 of " fog banks." 



The insular position of Ireland exposes it in a special way to the influence 

 of damp winds off the ocean, the prevalent ones in 

 Wet and Dry this region, as we have seen, being those from the 

 Winds. westward and southward. Those from the north and 



east, though not always dry winds, are usually so. 

 The meteorological element which tells perhaps most upon Irish farming 

 is precipitation — rain. Not that the rainfall is excessive, but its occurrence 

 is so precarious that the best attempts at forecasting, based upon past 

 experiences, however well systematised, are often foiled. Only in the east 

 of England — with a rainfall of less than 25 inches — is there a region 

 distinctly drier than any part of Ireland. The general 

 .... rainfall of the centre of England (25 to 30 inches) 



■ equals that of the centre of Ireland. In Cumberland, 



Westmoreland, Wales, and N. W. Scotland some 

 recorded precipitations are greater than in the wettest part of Ireland, which 

 is at Alangerton (118.8 inches in igoo). The wettest region in Ireland com- 

 prises the hilly districts along the west coast from Cork to Donegal (about 

 50 to 75 inches), extending inland so as to include the Waterford and 

 Tipperary Hills (about 40 ins.) The hilly district of Wicklow and South 

 Dublin is distinctly wetter than Middle and North Dublin ; and that of the 

 Mourne ^Mountains, though on the east Coast, is also a wet region in com- 

 parison with other parts of the County Down. 



That weekly and monthly averages are serviceable in agriculture, there 

 can be little doubt. Indeed the general consensus of opinion is to this 

 effect, judging from the number of stations at which records of rainfall are 

 kept even in Ireland (146 — see previous footnote p. 41). The manner in 

 which records of rainfall, temperature, etc., may be made to serve their 

 natural purpose has been admirably worked out in America : allusion is 

 made to this point at the conclusion. An obvious use to which Symons' 

 Tables of British Rainfall may be put, is that of classifying various regions 

 in Ireland according to the annual amount of precipitation. The records 



* Symons' Rainfall Map, "Modern Meteorology," p. 141. 



