QUATERITARY DEPOSITS OF BRITISH ISLES — BROOKS. 339 



obvious in the cuttings already made. Consequently none of them 

 knew of oak below fir in the middle of the bogs. But where a bog is 

 being cut on the edge of a basin, oak is found, and seems to extend 

 some way down the sides, in places being rooted in lacustrine marl. 

 For these reasons I conceive that Kinahan finding oak stools rooted 

 in marl on both sides of a basin and extending below the level of the 

 uncut peat, concluded that those on either side were both parts of 

 one forest which extended completely across the basin. The state- 

 ments in some of the Geological Survey Memoirs that stools of oak 

 were found " at the bottom " of the bogs are probably only to be 

 interpreted " on the floor " of the bogs. 



"VMiile there is some support for the two forest layers in the low- 

 land bogs, there seems very little in the upland bogs. Where a rough, 

 hummocky rock surface is covered by a bog there is in or on the 

 bog a very well-marked horizon of stools, which extends onto the bare 

 rock where the latter rises above the level of the old forest, but I 

 could not find a single instance in which tree stools rested on rock 

 below the level of this bed. Nor, so far as I am aware, have any 

 such been described. 



The upper forest layer is an exceedingly definite horizon all over 

 Ireland. The surface of the peat dried and remained firm for a 

 period probably of more than a thousand years; on it there gi'ew a 

 forest of pines. Some of the stools show 200 annual rings, and 

 they lie so closely together that several generations must be repre- 

 sented. P]ven in the west of Ireland, where no trees grow now, well- 

 grown forests extend up the hills to a height of about 500 feet, and 

 isolated trees to nearly 2,000. After a time, peat recommenced to 

 grow, killing the trees, and reached a thickness of from 20 to as much 

 as 50 feet, though almost everywhere the upper part has been removed 

 for fuel. In the west and in the central plains the peat is still grow- 

 ing on the cut surfaces, but in the east it has ceased to increase and 

 is being desiccated. 



In the old, submerged land surfaces which are common all round 

 the coast of Ireland, the upper, or fir forest commonly forms the basal 

 layer, overlain by a small thickness of peat where this has not been 

 removed, and this enables us to correlate the fir forest with the post- 

 raised beach elevation. On the raised beach flats, peat usually occurs 

 with a layer of stools of oak, fir, or hazel at the base. This is sup- 

 ported by the frequent appearance of stream sections in which a peat 

 bed with fir stools at the base is overlain by river alluvium, the de- 

 position of which must be due to a raising of the base level. 



It is the fir forest layer also which is chiefly of interest in con- 

 nection with the archeological remains found in the peat. These 

 belong to the neolithic, bronze, and iron ages, and it is the neolithic 

 which are chiefly associated with the forest horizon. They indicate 



