210 DAVIS : SECTIONS IN THE LIASSIC AND OOLITIC ROCKS OF YORKSHIRE. 
a large extent eastwards. In the neighbourhood of Hackness where 
these beds are largely quarried they are known as " Wallstones." 
Beyond Bickley the Greystone or Wallstone passes into a true 
grit with an occasional lenticular-shaped patch of fossils. This grit 
is much liable to weathering, and there are several detached blocks 
on the surface of the moor. Above Staindale are a number of them, 
one of which is 16 feet high and measures 80 feet in circumference. 
The Bride Stones are an example of this action ; the particles of sand 
are cemented together by silica, and to this is due no doubt its 
power of resistance as compared with the surrounding rock which has 
disappeared. 
The remaining portion of the Middle Oolites are best represented 
in the district about Hackness. The River Derwent and its tri- 
butaries have formed a series of deep valleys which are not only 
interesting geologically, but constitute some of the finest inland 
scenery in the country. One of the hills on the east side of the 
Lowedale Beck, and about half a mile north of the village of Hack- 
ness, exhibits a very complete series of beds between the Kelloway 
Rock and the Upper Calcareous Grit. The former rock may be seen 
at the base in the valley ; above it, rising in the hill, is the Oxford 
Clay, considerably diminished in thickness. The succeeding series of 
strata are exposed in a disused path, which is half water-course after 
heavy rain. It is reached by a road opposite St. Peter's Church, 
which passes Silpho. After proceeding a short distance the path is 
seen branching off to the left, whilst the road by zig-zag turns 
ascends the hill. The Lower Calcareous Grit succeeds the Oxford 
Clay and is exposed in the lower part of the path, gradually chang- 
ing in its upper strata to the Passage Beds, and they in turn giving 
place to the Lower Oolitic Limestone, with the Coral Rag at the base. 
Still exposed on the hill-side is the Middle Calcareous Grit, and. 
forming the summit of the escarpment is the Upper Oolitic Lime- 
stone, with Coral Rag at the top. The latter extends over the surface 
of the hill for some distance. The last in the series is a small 
detached outlier of the Upper Calcareous Grit, the uppermost bed of 
the Middle Oolites, 
