ON PEAT MOSS DEPOSITS. 413 
Characteristic plants. Accompanying plants. 
8. Light-coloured tenacious clay mixed 8. 
with fine sand. 
9. Gravel. 9. 
The presence of peat formed from aquatic plants below the arctic zone 
is an interesting feature, and suggests that the summers of that time were 
fairly warm and long enough to allow these aquatic plants to seed freely. 
Similar aquatic beds below the basal arctic zone have been found during 
the examination of the peat in the Cape Wrath District, and in the 
Shetlands.! 
Between Allt Bad Eauring and Garbh-allt (two small burns flowing into 
Dyke Burn) the banks of Dyke Burn are about 3 feet high and formed of 
peaty sand. Rather below the summer level of the burns occurs a layer 
of leaves and small twigs mixed with sand. This rests upon water-sorted 
glacial deposits. This leaf bed is chiefly formed by the leaves of creeping 
willows—Salia reticulata, 8. arbuscula, and stems of Potentilla Comarwm. 
The material is certainly drift, owing to the thin layers of sand between 
the leaves, but it does not bear evidence of having been carried far, as the 
bark on the twigs and the leaves are quite uninjured. In the upper 
portions of the leaf bed twigs of Betula alba are fairly abundant. This 
bed was traced for about half a mile, and sections dug at intervals all 
showed the same features, but the bed is thickest and best seen at sharp 
bends in the stream. 
Owing to this bed being only two miles from the summit of Ben Griam 
Beg (which rises to 1,903 feet) it seemed at first possible that it repre- 
sented the débris of arctic willows now growing on the summit, but a 
careful examination of the vegetation on the summit and flanks of the hill 
showed no trace of any creeping willows. The thickness of the bed and 
the uninjured condition of the plant remains suggest that they were 
deposited by a slow stream, and therefore through a fairly lengthy period. 
The succession amongst the moraines probably indicates the origin of the 
material forming the leaf bed. The upper zone of forest there is under- 
laid by a bed of arctic plants resting upon a lower zone of forest, and it 
seems most probable that the leaf bed was formed during the growth of 
the intercalated arctic plants. 
Sections in the Strathy Basin.—The whole drainage area of the river 
Strathy (about fifteen miles in length) is covered with an unbroken sheet of 
deep peat. This was examined at many different points to within five miles 
of the sea. Northward of this the peat becomes shallow and is inter- 
rupted by many outcrops of schist. 
The following section shows the general succession met with :— 
Characteristic plants. Accompanying plants. 
1. Scirpus cespitosus. 1. Sphagnum, Eriophorum vaginatum. 
2. Pinus sylvestris (trees rather small, 2. 
but forming a definite layer). 
3. Eriophorum vaginatum. 3. Sphagnum. 
4. Betula alba (wood generally much 4. 
decayed, but bark plentiful and well 
preserved), 
5. Hriophorum vaginatum. 
ct 
. Menyanthes  trifoliata,  Potentilla 
Comarum. 
. Saliva reticulata. . Arctostaphylos alpina. 
. Boulders with intervening spaces 
packed with coarse sand and grit. 
AS 
NG 
1 «The Plant Remains in the Scottish Peat Mosses,’ Part III., Trans. Royal Soe. 
Edin., vol. xlvi. 1907. 
