On the Geology of Northumberland. 123 
east parts of Northumberland. I examined several of these 
places about four years ago, and found them to consist of green- 
stone rocks seemingly deposited above the independent coal _for- 
mation. This is the case with the rock on which the castle 
stands in Haly [sland. The basis of this island is limestone, 
The sawie thing occurs at Bamborough Castle, and in severai 
hills in the neighbourhood of Belford, These facts may have 
some interest to the geologist, though I did not consider them 
of sufficient importance to interrupt the general view of the 
structure of these counties which I have now given.” 
_ Though it may appear presumptuous to differ from so able a 
geologist; yet i am led to think that had Dr. Thomson investi- 
gated the rocks at Dunstanborough Castle, at Gunwarden near 
Barwesford on North Tyne, but especially at Wratchiff Crag 
~ near Aluwick, the stratification exhibited at these places would 
have induced him to draw a different conclusion; for there he 
would have seen the basalt alternate with the rocks of which the 
- whole district is composed. 
At Dunstanborough the cliffs consist of 
1. Columnar basalt .. .. Sto 10 feet. 
2: Handstoner” isc ows. 12feets 
3. Shale (slate clay) .. =... 6 feet. 
4. Basalt to below the water’s edge. 
At Gunwarden—strata of dark-blueish-gray crystalline lime- 
stone, from 3 to 4 feet thick, alternate twice with compact ba- 
salt. This limestone contains a considerable portion of iron; and 
in colour, lustre, aud the shape of its fragments, so nearly re- 
sembles basalt as to render it liable to be mistaken for that sub- 
stance, To the lime-burner it is of no use. In the neighbour- 
ing rivulet casts of the Madrepora flexuosa, mineralized by flinty 
slate, or more properly indurated slate clay, have been detected. 
But Wratehiff Crag having been queried of late years to a 
considerable extent, aud the different beds of which the hill is con- 
structed laid open to view, strengthens the opinion that no floetz- 
trap formation exists in Northumberland. The following section, 
accompanied by specimens, was communicated to me by a friend 
whose accuracy my be depended upon. 
1, Compact basalt, imperfectly columnar .. 20 feet. 
2. Indurated slate clay, resembling porcelain jasper 3 feet. 
3. Enerinal limestone (containing also bivalve 
shells) of a dark-brownish gray colour, glim- > 8 feet. 
mering lustre, and splintery fracture .. 4. 
4, Slaty marl .. eth eed ind Seen ual Sinebes, 
5, Crystalline linisiane of a light blueish-gray 
colour, glistening lustre, and fine granular $ 3 feet. 
texture ee ef ee ee ee ef . oe 
6. Slaty 
