9 2i Proceedings of ihe Royal Irish Academy. 



it probable that not merely the climate but also the soil must have deterio- 

 rated long before historic times, and since the Oak spread throughout the 

 west. With the present soil conditions, the Pine, which at one time was 

 universally distributed over Ireland, would have a better chance of 

 maintaining its footing than the Oak, and could scarcely have been crushed 

 out by the latter. Yet there are good reasons for supposing that this actually 

 occurred. 



Whether this deterioration of the soil and the growth of peat was a 

 direct result of climatic change is an open question. As already pointed 

 out, there are good reasons for assuming a heavier rainfall and cooler 

 summers at the present time than those of two or thi'ee thousand years ago, 

 when dry heath probably occupied the surface now covered by mountain 

 peat, and the more extensive growth of Sphagnum peat had not commenced. 



The general conclusion at which one must arrive after reviewing the 

 whole of the facts regarding the comparative absence of trees in the west 

 of Ireland is, that after making due allowance for human interference, 

 grazing, and other artificial causes, the present soil and climatic conditions 

 are not those which prevailed at the time Oak and Hazel pushed their 

 way to such extremely wind-exposed points as Clare Island, and colonized 

 the whole of the mainland within 1000 or 1200 feet of sea-level. Warmer 

 summers appear to have been the most likely feature which characterized a 

 former climate, but whether these were accompanied by a lighter rainfall 

 and a reduction in westerly winds is not so clearly suggested by the evidence 

 available in the west of Ireland alone. An extension of the land, ten to 

 twenty miles further west, which is suggested by geological evidence of changes 

 in the sea-level, would place the present coast-line far enough inland to 

 enable trees growing along that line to escape the worst effects of the sea- 

 wind, and while the beneficial effect of this would be somewhat discounted 

 by the higher elevation at which trees on existing land areas were growing, 

 there is some reason to suppose that a lowering of the present sea-level by 

 100 feet or so would lead to an increase in summer temperature, and a 

 reduction in the rainfall of lowland districts. 



The year 1913 appears to have provided a good example of the effect of 

 temperature upon the ripening of wood, resulting in a greater resistance to 

 wind in trees throughout the Blacksod and Louisburgh districts. Exposed 

 trees of Ash, Sycamore, Oak, Hazel, Thorn, &c, show large numbers of well- 

 ripened and uninjured shoots ; so much so, that many trees have partially 

 lost their characteristic wind-swept appearance for the time being. Two 

 wind-swept Oaks at Old Head, with flattened tops, and about 10 feet in 

 height, possessed well-ripened 1913 shoots of 12 to 24 inches in length 



