46 MR FRANCIS J. LEWIS 



equal portions of land and water. Whilst many of the lochs are deep with rocky 

 basins, others are merely hollows in the deep peat. The condition of the peat over this 

 great area (where the conditions for peat formation are perhaps more favourable than 

 in any other part of Great Britain) entirely confirms the conclusions reached by Gkikie 

 (5) many years ago, as to the present rapid denudation going on in our peat bogs. 

 Here is an area on the confines of the European plateau, exposed to Atlantic conditions 

 and therefore having a moderate temperature, a heavy rainfall, and a moist climate — 

 all conditions that are favourable for the growth of peat. In this area we find peat 

 covering the floors of the valleys and the hillsides to a considerable depth, yet at the 

 present time the peat is wasting away much faster than it is being formed. A traverse 

 taken across the island from Barvas to Monung (the solitary hill rising to 800 feet in 

 the north of the island), and from Monung to Stornoway, shows that for the greater 

 part of the way the peat is cut up into a system of vegetation-covered ridges or banks 

 separated by channels about 4 feet broad and 3 to 4 feet deep. Further, the wastage 

 is, as we should expect, more noticeable on rising ground and hillsides, than on the 

 levels, and is more marked as the eastern seaboard of the island is approached than on 

 the west. Although this feature could be explained in some particular mosses by the 

 raising of the surface, due to the activity of the peat-forming plants, the raised bog 

 permitting freer drainage and thus paving the way for the succession of less actively 

 peat-forming plants, such as the heather and hill-pasture associations, yet the feature 

 is so universally present on all types of peat-bogs, on hill-tops, hill- slopes, and in 

 valleys both in England, Scotland, and Ireland, that the ultimate cause must be sought 

 beyond any such local and episodal events such as I have suggested. It is true that 

 the present denuded condition of the peat is due to a change of vegetation, but the 

 general replacement of Sphagnum associations and marsh vegetation by Calluna 

 associations must be due to some cause operating over the whole of Britain, such as a 

 general decrease in the humidity of the climate. 



The genera] vegetation of the peat mosses shows a close resemblance to those on 

 the N.W. districts of the mainland. Calluna is fairly abundant, mixed with Scirpus 

 casspitosus, Rhacomitrium lanuginosuyn, stunted Vaccinium Myrtillus, Potentilla 

 reptans, Erica Tetralix, Narthecium ossifragum. 



Sections were made in three different areas in the Lews : — 



(a) In the centre and east of the island, to the S. and S.W. of Monung. 



(b) South of Barvas, and also in the basin of the river Bragor. 



(c) Submerged peat in Sandwick Bay, near Stornoway. 



(a) Peat Mosses South and South- West of Monung. — These lie at a general 

 elevation of 200-400 feet, and form gently undulating moorland in the drainage system 

 of the Gress river. The area contains many small lochs, some of which occupy hollows 

 in the peat. 



In some places the remains of an arctic type of vegetation occurs at the base of the 



