426 ON THE SUPEEFICIAL STRATA 
iill^ or red tilly earth, as the case may be, which rest on 
the old red sandstone. 
The mosses alluded to have preserved the remains of an 
ancient forest, chiefly oak-trees, which had occupied the 
plain but little above the surface of the river during ordi- 
nary floods, part \^'hereof appears to have been lower and 
marshy, across which a road had been formed of trees laid 
longitudinally, with a second layer transversely. The d^th 
of Blair-Drumraond Moss (in which this road occurs), prior 
to the operations, was eight feet, extending to fourteen to- 
wards the upper extremity. Some of the roots of the trees 
were very large, and occupied their natural position in the 
soil, their trunks being extended horizontally, many retain- 
ing distinct impressions of the axes employed in felling 
them an operation commonly referred to the period of 
the Roman Conquest *. 
These remarks on the upper district apply equally to the 
lower district and its mosses. But although the carse-clay 
soil presents in both the appearance of an extensive level 
plain, it is perhaps nowhere perfectly horizontal. It con- 
tains depressions, elevations, and inclined planes, which, to 
a certain extent, seem to have modified the course of the 
Forth, assisting in the formation of those meanderings 
which distinguish it, and which, particularly on the exte- 
rior margin of its numerous circular sweeps, encroach on 
the higher banks, presenting perpendicular sections on that 
side, and leaving low ground on the opposite, commonly 
embanked against the higher tides. In the lower district, 
the carse-clay has been remarked from SO to 70 feet in 
thickness, at sinking wells near Stirling and Bothkennar. 
It reposes on sand, gravel, dark-blue till^ or immediately 
on rocks of the Coal Formation. In both districts, the 
* See " Encyclopaedia Britannica," article ' Moss.' 
