OF THE COUNTIES OF NORTHUMBERLAND AND DURHAM. 221 
approach towards the sea they become deep and narrow, with 
precipitous masses of rock on either side, covered with foliage of 
luxuriant growth. Occasionally they are widened out into large 
amphitheatres, with sloping banks covered with trees and rare 
and peculiar plants, and afford shelter and food for many in- 
teresting animals. The coast-line is rather varied, and the cliffs 
generally low, but in a few instances where hills occur on the 
coast, the cliffs are high and precipitous. In several places 
along the coast, large picturesque masses of wave-worn rock, na- 
tural arches, and islets, which have been separated from the 
general mass of limestone, break the uniformity of the coast scene. 
Except in the south of the county of Durham very few sands oc_ 
car, and these happen only where the limestone has been former- 
ly denuded to the sea level. 
All the above appearances, perhaps, are referrible to the va- 
riable nature of the limestone, some parts of which are very 
earthy and rubbly, and easily worn by the action of water, where- 
as other portions are hard and compact, and able to withstand 
the strongest denuding force. 
In many localities between Boldon Hill and Midderidge 
Grange, at the base of the escarpment before mentioned, a bed 
of coarse incoherent sandstone of very variable thickness, and ge- 
nerally of a yellow colour, is situated. Beds of a reddish micaceous 
sandstone, more coherent than the former, and bands of red or 
dark coloured marls are oftentimes associated with it. These beds 
are at the base of the formation in this district, and rest more 
or less unconformably on the coal measures. They are the 
“ Lower-new-red-sandstone” of English Geology, and from their 
relative position, are considered equivalent to the “‘ Rothe-todte- 
liegende” of Germany. In Northumberland, the former of these 
beds is seen in the cliff at Cullercoats Bay, and the latter is 
well exposed near Tynemouth Haven. Fragments of a Lepido- 
dendron and a Calamite have occasionally been found in the 
sandstone quarries between South Shields and Westoe, where 
the last mentioned bed is of great thickness. 
A small deposit of “ Marl-slate,” equivalent to the “ Kupfer- 
schiefer” of Germany, generally succeeds. It very rarely ex- 
