338 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1917. 



severe climate than the present. I have already mentioned the 

 grounds on which I regard the " head " of the south coast as belonging 

 to this recurrence of cold conditions rather than to the period of the 

 upper bowlder clay. Similarly many coarse river terrace gravels and 

 delta deposits probably belong to the same period, though proof is 

 difficult. I Avill merely pick out a few striking examples. I have 

 already mentioned the gravel terraces near Londonderry. Some of 

 the post-upper bowlder clay terraces of the Liffey and other rivers 

 are very coarse, indicating torrential action; these would probably 

 repay further investigation. The remarkable frequency with which 

 tree stools, especially oaks, are rooted directly in lacustrine marl, 

 without any intervening marsh deposit, suggests some break in the 

 succession, the lake's outlet being cut down and its bed drained under 

 conditions not favorable to vegetation. 



In Killimor Bog, County Galway (Memoir sheets 115 and 116, 

 1865), peat rests on lacustrine marl and is covered b}' alluvium. The 

 originally horizontal lamination of the marl has been crumpled, as 

 though by a powerful horizontal pressure, and the surface planed 

 smooth, before the formation of the peat. This strongly suggests 

 the " warp " of river silts, which is due to floating ice. 



The uppermost superficial deposit over a great part of Ireland is 

 peat, which covers one-seventh of the country to a depth ranging up 

 to 50 feet. Peat bogs are of two main kinds, lowland or red bogs, 

 mostly composed of the accumulated remains of marsh plants, grow- 

 ing in a lake or swampy hollow, and mountain bogs, much tougher 

 and of slower growth, formed by a close mat of heath plants which 

 can extend up or down quite steep slopes, even over porous 

 rock, as well as occupying flat hilltops. In the west of Ireland the 

 mountain bogs descend also onto the plains, displacing the red bogs. 

 The two chief points of interest are the buried forests and the 

 archeological remains. 



Remains of oak, fir, pine, hazel, and other trees occur everywhere 

 in the bogs, including branches and fruits and also stools rooted in 

 the underlying bog or rock. Mr. G. H. Kinahan (e. g., 1878) stated 

 very positively that these tree remains form two well-marked forest 

 horizons, one at the base of the peat and the other some feet above it, 

 but this has frequently been contradicted. My own conviction is that 

 the two horizons certainly exist in some bogs, but that in some 

 others the conditions were not suitable for its development, while as 

 regards the great majority of the bogs we are totally ignorant. I 

 examined a number of peat cuttings in County Cavan, but could not 

 find one which went down right to the bottom of the peat near the 

 center of a basin. In response to my inquiries I was always in- 

 formed by the cutters that in the middle of the bogs they never cut 

 to the bottom because the peat is too wet there; the latter fact was 



