9 6 Proceedings of the Hoijal Irish Academy. 



brought in contact with well-aerated soil or water containing lime. Streams 

 and springs on the surface, if they do not prevent peat-formation, check its 

 accumulation, while no peat forms on the margins of streams which periodically 

 overflow their banks and leave a muddy deposit behind. Peat-accumulation 

 increases with the degree of acidity, and this beiug greater the further the 

 surface lies from the water-table, the centre of the bog naturally increases in 

 thickness at a faster rate than the sides. 



On Clare Island, mountain and marsh peat are well represented, but high 

 bog, owing to the long duration of peat-cutting, is not much in evidence. 

 The largest marsh bog originally surrounded the small lake known as Lough 

 Avullin, which at one time covered ten to twenty acres of the valley in which 

 the lough lies. This lough is fed by the most extensive drainage system on 

 the island, but an artificial cutting, about 10 feet deep, near the bridge on the 

 east side, has now rendered much of the bed of the ancient lake dry. From 

 the distribution of Oak and Pine stumps in this valley and elsewhere, it would 

 appear that Lough Avullin at one time occupied a more or less elongated 

 depression, chiefly to the south-east of the present water, on the margins of 

 which Pine was the principal tree. At a later period the water gradually 

 rose and covered these Pine margins with marsh or swamp, killing out the 

 trees on the lower levels. Either during the time the water-level was slowly 

 rising, or after it had ceased to rise, Oak apparently spread into the Pine 

 forest and gained a footing on the marsh round the edges of the swamp until 

 the water-table of the latter again rose, killed out the trees, and brought the 

 peat up to its highest level. It is probable that this marsh peat was capped 

 with high bog, but no trace of this now remains, as the greater part of the 

 valley has been cultivated in recent times. 



Several smaller marsh-bogs occupy depressions to the south of Lough 

 Avullin swamp, and within 200 feet of sea-level. All of these contain stumps 

 of Pine and Oak, the former occupying the central parts and lower levels of 

 the bogs, and the Oak appearing round the margins. This series of bogs all 

 show the same features, whether as regards marsh-peat, the occurrence of 

 Pine in the deeper parts, and the mingling of Oak with the Pine at the edges, 

 and may be termed, for the sake of convenience, the Pine and Oak group. 

 Extensions of this group appear to have existed between the harbour and 

 Knocknaveen, towards the chapel on the south side of the island, and a small 

 Oak stump was noticed near the chapel, resting on about 4 feet of peat. 



The size of the Pine stumps in this group varies from 1 to 3 feet in 

 diameter at the ground -level, probably corresponding to breast-high diameters 

 of 1 to 2 feet. Only one log of Pine was noticed, which had a straight length 

 of feel, and a crooked top of 8 feet, with a diameter of 8 inches 4| feet from 



