428 ON THE SUPERFICIAL STRATA 
mosses of either district. I have particularised these hol- 
lows, because in the points which were at all seasons free 
from flooding, the roots of vegetables, with the operations 
of insects, producing a more spongy texture, and affording 
access to the influence of the sun and air, a more equivocal 
description of clay is presented, approaching to vegetable 
mould. Undisturbed clay is further indicated by alternat- 
ing thin parallel layers of blue and brownish clay, in which 
occur, in both districts, many extensive deposits of marine 
shells, disposed conformably to the layers. Their localities, 
with other remarks applicable to the general subject^ shall 
next be noticed. 
Sp. 1. — Below Polmaise, the south bank of the river 
presents sundry sections of the carse-clay. Near Fall-in, is 
a section of 14 feet : under the soil-cover, 8 feet of the alter- 
nating stratification, formed by extra proportion of quartz, 
grains, oxide of iron, and mica-scales; declination E. 5°. 
Beneath this, a layer of shells occupies the clay, from 6 to 8 
inches in thickness, same as in specimen. It also contains 
in abundance the roots of paddoclc-pipes (the Equisetum), 
which plant is frequent in the surrounding fields. These 
roots do not appear under this layer. Some of them pene-= 
trate into the interior of the shells. Under this lies a con- 
formable stratum of peat-earth (14 inches), sides parallel, 
containing numerous fragments of the rind of an aquatic 
reed, compressed longitudinally ; also small pieces of wood, 
and fragments of bark ; but no trace of the moss-plants, or 
bog-plants, which form the superficial mosses of the valley. 
Sp. % is from this stratum, situate 6 feet above high- 
water mark : under it lies a more compact and bluer clay. 
Eastward 300 yards, the bank presents a similar disposi- 
tion, with declination E. 3^. In all these the shells con- 
sist of the kinds most common in the Frith and sea-coast. 
Many of the bivalves occur shut and empty, excepting a 
