LOWER CHALK. 
yi 
its course. It is regularly stratified, the lines of 
separation being composed of a softer chalk, that 
in some j)laces. contains so great a proportion of 
argilla as to form veins of marl. The latter sub- 
stance also occurs in transverse and vertical veins, 
in which the remains of fishes are more frecpient 
than in the more solid strata. 
The general inclination of the beds is towards 
the south-east, at an angle of from 5 ° to 15°. 
Their total thickness has not been determined, 
but is probably not less than ^200 feet. A well 
sunk on the side of the hill, near Glyndbourn, 
passed through 120 feet of the lower chalk 
only. The lowermost beds were of a deeper grey 
than the upper, but presented no other material 
variation. The cliffs that extend from near 
Beachy Head to Southbourn expose this bed at 
their base, and afford considerable facility for its 
investigation. 
Near Lewes, the lower chalk occurs in the 
quarries at the foot of Mailing Hill, Southerham, 
Glynd, Glyndbourn, Swanborough, Plumpton, 
&c. ; and in other parts of the county, along the 
northern edge of the Downs, reposing immediately 
on the grey chalk marl. 
The quarry at Southerham is remarkable for 
the inclination and direction of its beds : it is 
situated on the east side of the road, on the south- 
western extremity of Cliff Hills. It is about 
thirty feet high, and contains from eight to ten 
layers of chalk, the latter varying in thickness 
from one to eight feet, being separated from 
each other by intervening seams of friable chalk 
