340 MR FRANCIS J. LEWIS 



The upper layers of birch are always mixed with abundance of Corylus Avellana, 

 the wood, bark, and nuts being in an excellent state of preservation. When, however, 

 the lower layers are examined, the wood in most cases has disappeared, and layers of 

 birch bark are the only plant remains met with, imbedded in dry hard peat, which itself 

 shows no distinguishable plant remains. In other words, there seems to be a break in 

 continuity between the upper and lower layers of the same forest-bed. The same 

 appearance has been noticed in North Uist. This feature may only mean that the 

 lowest layers being dry and much compressed, the wood has shrunk and disintegrated, 

 leaving only the bark to mark its former existence ; or it may mean that after the lowest 

 layer of the birch forest had been deposited a prolonged period of denudation set in, 

 during which the birch stems were exposed to atmospheric agencies, thus causing the 

 wood to disintegrate. This is a point which can only be solved by further observations 

 on the Hebridean peat over large areas, but it may be remarked in passing that the 

 feature is illustrated over areas in England where peat denudation is at present going 

 on. In the Cross Fell district in Cumberland large areas of bare peat denuded down to 

 the birch horizon occur, and the birch wood has frequently quite disintegrated, leaving 

 only the bark intact. If birch wood again spread over such areas and the remains were 

 sealed up in quickly forming peat, exactly the same features would be presented in a 

 section as we find in the birch zone of Skye and Uist. 



In the absence of any unmistakable datum line, it is impossible to correlate the layers 

 in the Hebridean peat with those described from the Eastern Highlands and elsewhere. 

 The general succession agrees closely with that in the lowland mosses in Kirkcudbright- 

 shire, and the view that has perhaps most to recommend it is, that the basal birch forest 

 of Skye and North Uist is contemporaneous with the lower forest of the Kirkcudbright- 

 shire peat. If that reading be correct, the upper forest zone is wanting in Skye and 

 North Uist, and its place is taken by beds of such plants as Scirpus, sp., Phragmites, 

 Equisetum, Sphagnum, and Eriophorum. The absence of the upper forest-bed that has 

 been observed by the author in several districts in the extreme north and west is 

 interesting, as it may mean that the conditions suitable for the growth of forest on deep 

 peat did not obtain over the areas of greater precipitation in the west ; but the complete 

 correlation of the beds from the Hebridean peat must be deferred until more areas in 

 the Outer Isles and North- West Mainland have been investigated. 



The North- West District of North Uist. 



(One-inch Ordnance Survey — sheet 89.) — With the exception of small pasture areas, 

 chiefly in the west, the whole of the island may be said to be peat-covered, and in 

 many places the deposits appear to be of considerable depth. Sections were made 

 chiefly in the Ben Aricaiter and Marrival district, but much of the southern and central 

 parts of the island were walked over and the peat-hags examined for evidence on the 

 characters of the upper zones of peat. Sections were first made on Sgurr nan Carrach 



