OF THE COUNTIES OF NORTHUMBERLAND AND DURHAM. 225 
the cliff is rather low, and composed of numerous beds which are 
hard, strong-bedded, and flag-like, associated with others which 
are more earthy in structure. At Byers’ Quarry, a thin, crys- 
talline bed occurs, in which a few shells are preserved. The 
same kinds are also found in some of the earthy beds further to 
the south. To the north of Whitburn, a bed of limestone, of 
small concretionary structure, appears in the cliff. This is fol- 
lowed by another, which is very strong-bedded and earthy, but 
before reaching Whitburn Sands, a bed, composed of globular 
masses, is seen at the base of the cliff. For about two miles 
along the coast the limestone disappears, but near Roker the 
last-mentioned bed occupies the whole of the cliff, which is here 
not very high. The globular concretions in this part of the bed 
vary from the size of a pea to more than a foot in diameter. At 
Fulwell, a short distance from the coast, this bed occurs with 
others of a more complicated structure. A piece of this rock, 
when the concretions are of a small size, very much resembles a 
bunch of grapes, and hence has been termed botryoidal limestone. 
It is called cannon-ball limestone when the concretions are very 
large. Many of the concretions in these beds are not solid, but 
are formed of lamine, partly united, leaving numerous regularly 
arranged cavities, filled with a powdery substance between the 
harder parts. When cleaned from this powder, pieces of this 
rock slightly resemble a portion of honey-comb, and consequent- 
ly this variety has been termed honey-comb limestone. Beds 
identical with these occur in much the same form at Building 
Hill, near Sunderland, and slightly modified in the cliff between 
Hendon and Ryhope, and in an adjoining quarry. The lime 
stone here resembles masses of coral compressed together, and 
might be termed coralliform limestone, if a distinctive name 
were required. At Roker the globular masses sink for a short 
distance beneath the surface, and a thick bed of light-coloured, 
earthy limestone resis on it. This bed is composed of numerous 
thin layers which have a grooved appearance on the face of the 
cliff. The beds between Ryhope and Castle Eden are either of 
a laminated or of a coarse concretionary structure, resembling 
those which occur near Shields; but near Black Halls, a short 
