LAMPLUGH : EARTH-MOVEMENT IX NORTH-EAST YORKSHIRE. 387 
the anticline towards the Humber, we may be fairly certain that it was 
never anything like so thick on the crest as in the Vale of Pickering. 
In any case, the Upper Cretaceous unconformity itself proves that the 
northern area was still further depressed relatively to the south during 
the closing stages of the Jurassic, and probably also during a large 
part of Lower Cretaceous times, while the Speeton Clays were being 
deposited. We may therefore, I think, use the Eed Chalk as a datum- 
plane to round off our investigation ; but its value is impaired by the 
fact that it now remains in the southern part of the district only, 
and cannot safely be assumed to have maintained the same attitude 
in its former northward prolongation. 
For the purpose of analysing the inter- Jurassic movements, it 
will suffice to consider the following six planes, as the others enumerated 
are less conveniently spaced, besides merely repeating the evidence. 
6. Eed Chalk. 
5. Corallian Limestones. 
4. Cornbrash. 
3. (a) Millepore Bed (southern area) ; (6) Grey Limestone 
(northern area). 
2. Dogger. 
1. Rhsetic. 
Relative Position of the Planes. 
We fortunately possess full data respecting the position of the 
planes in the admirable series of Geological Survey maps, sections, 
and memoirs embodying the work of the late C. Fox-Strangways 
and his colleagues ; and the exceptionally close contouring (25 feet 
intervals) of the 6-inch Ordnance maps, the basis of the geological 
work for this district, affords unusual facility for calculating the 
levels from the position of the outcrops. The published " Horizontal 
Sections " of the Geological Survey in particular show the relations 
of most of the planes, on a true scale, in various directions across the 
district. But on these long sections, drawn to the same scale vertically 
as horizontally, it is impossible to bring out distinctly the salient 
points of the structure as a whole, not only because of the scale, but 
also because the dominant characters are frequently obscured by local 
accidents of undulation and faulting. To render the matter explicit, a 
diagrammatic treatment of the facts is requisite, with the elimination of 
