es 
SECTIONAL TRANSACTIONS.—K. 453 
western facies, at low altitudes (‘ valley moors’). The peat of these British- 
raised mosses seems to be built up mainly by Sphagnum magellanicum, 
which is also the most important peat former in the west of Sweden. The 
pure, undecomposed SS. fuscum peat, characteristic of the raised mosses in 
great parts of Europe, does not seem to occur in the British Isles. ‘Types (d) 
and (e) are the characteristic mosses of Great Britain ; in these, Sphagna 
grow less vigorously than in the other types, the most important species 
being S. magellanicum, S. rubellum and S. plumulosum. On the other hand, 
Scirpus cespitosus and Eriophorum vaginatum are rather prominent peat 
formers. Consequently the peat in these mosses may be characterised as 
Scirpus cespitosus-Sphagnum peat, Eriophorum vaginatum-Sphagnum peat, 
or, especially in the Pennines, pure Eriophorum vaginatum peat, all of them 
being fairly well decomposed. 
On the mosses in the British Isles wind erosion plays a rather important 
réle, forming a complex of hummocks and depressions. On the hummocks, 
Rhacomitrium is often abundant, forming a Scirpus-Rhacomitrium or a pure 
Rhacomitrium peat. 
An interesting feature of the vegetation of these British peat areas is the 
relatively high frequency of many plants, which do not grow on the typical 
raised mosses of the continent, for example, Polygala vulgaris, Potentilla 
erecta, Narthecium ossifragum and Molinia cerulea. 
Dr. A. RatstricK.—Conditions of peat formation in the Pennines (11.0). 
The peats of the Pennine area can be grouped under four distinct types : 
(a) Fell top peats, on the flatter summits above 1,500 ft. O.D.; (6) Valley 
head peats, in sheltered hollows about 1,000 to 1,600 ft.O.D.; (c) Channel 
peats, in areas of anomalous drainage, mainly glacial overflow channels at 
all levels ; (d) Pond and lake peats, in the glacial lake sites, mainly in the 
valley bottoms. 
The longest record of conditions is preserved in the deposits of the glacial 
lake flats. These start with a great depth of laminated clays and silts, 
followed by fine sands with peaty material or pollen, and then by coarse 
sands or boulder gravels. Above this may be two true peat beds, separated 
by gravels, and covered finally by river terraces. Peat formation in the 
lakes and the valley heads commenced in the upper Boreal period, the base 
of the Atlantic being marked by the boulder gravels in the lakes, and by 
occasional erosion levels in the peats. ‘The increase of run-off led to the 
breaching of the lake morainic dams, and resulted in a marked change of 
physical conditions over the whole area. Peat accumulation continued 
through the Atlantic period, the peats spreading to the fell top areas, 
and marked by at least two ‘ forest’ layers, of birch twigs, and stools of 
birch, oak, and (rare) pine trees. The hill top peats may be from 15 to 20 ft. 
thick, but almost everywhere have now an eroded upper surface. The 
upper part of both fell top and valley head peats is of sub-Boreal type, 
but shows marked increase in sphagnum and cotton grass, and decrease in 
the quantity of tree pollen present. A sub-Boreal peat is present in some 
of the lake sites. Peat formation slowed down or stopped during the 
sub-Boreal and sub-Atlantic on all the higher sites. ‘The channel peats 
are all soft and wet, and very difficult to investigate; they are largely 
sphagnum peats, but their growth has been continuous in many cases to the 
present. Archzological remains are associated with many of the lake sites 
and with some of the hill-top peats, and these confirm the dating suggested 
by the tree pollen. 
