xl INTEODUCTION. 



so that its effect on Irist climate must be quite inappreciable. 

 It is probably to the prevailing south-west winds, travelling over 

 wide ocean areas before they impinge on the Irish coast, that our 

 more equable and humid climate is due. Experiments conducted 

 by Dr. Humphi-ey Lloyd, in 1851, showed that the temperature of 

 the sea ofl the west coast of Ireland exceeded that of the aii- on 

 land by 1-8° Fahrenheit in summer and 6-7° in winter. 



The influence of the vapour-laden south-west winds is clearly 

 shown in the distribution of the Irish rain-fall, which reaches its. 

 maximum in the south-west, where the lofty Eerry mountains act 

 as condensers, while it decreases in a marked degree towards the- 

 east and north. The mean annual rain-fall at Valentia for the six 

 years, 1890-96, was 53-6 inches, while in wet years, both here and 

 at Killamey, another south-western station, the total annual rain- 

 fall has risen to 61 inches. For the same six years the mean at 

 Markree, in SUgo, a western station some 150 mUes northward of" 

 Valentia, was 40-5 inches. On the eastern side of the island, 

 Dublin city for the same period gave a mean of 26'5 inches, and 

 Ajmagh of 29-3 inches. The amount of the decrease in rain-faU 

 from west to east varies greatly according to the position with 

 respect to mountain masses of the stations compared, and the number 

 of stations for which statistics are available is too small to permit 

 of any trustworthy average being arrived at for the west and east 

 coasts. But we are concerned here only with the broad features of 

 the Irish climate, and one of these is unquestionably the general 

 contrast in humidity between west and east. 



To these climatic differences between the two sides of the island, 

 certain differences in the vegetation may be directly ascribed, as 

 well as differences in the respective floras. In the west, the pro- 

 portion of the vegetation, or total mass of plant life, which is made- 

 up of individuals belonging to the moisture-loving orders — Cype- 

 racese, Eushes, Ferns, &c. — is much largerthan in the east; and a few 

 species, which are confined to the west and south-west, such as 

 Silthorpia europma, Mioroeala fiUformis, and Saxifraga Geum, are 

 perhaps so confined by the absence elsewhere in Ireland of the degree 

 of humidity and equability of climate necessary to their maintenance.. 



III. The Ieish and English Fioeas compared. 



Viewed as a whole, the flora of Ireland may be regai-ded as an 

 incomplete English flora, as this in its turn may be regarded as an 



