LAMPLUGH : NOTES ON THE WHITE CHALK OF YORKSHIRE. 173 
recess of Filey Bay and the broad low Vale of Pickering mark the 
emergence of the Lower Cretaceous and Upper Jurassic Clays from 
beneath the Chalk escarpment. The indentation to the southward of 
the headland is due partly to the less resistant nature of the upper- 
most portion of the Chalk itself as compared with the lower, and 
partly to the great curve which occurs in the strike of the strata after 
entering Yorkshire. 
Part I. Description of the Photographs. 
1. Speeton Gap. 
The first of the photographs shows the clitf at Speeton where the 
Lower Cretaceous Clays emerge from beneath the Chalk. The point 
of view is near iow-water mark on the shore opposite the mouth''- of 
the little ravine known as Speeton Gap, looking southward. To 
facilitate the explanation of this plate (and also of Nos. 2 and 12) an 
outline key on a reduced scale is given in Plate xxxiv. to which refer- 
ence should be made. The low ridge in the foreground to the right 
of the ravine is composed entirely of Speeton Clay {Division B. ; Zone 
of Bel. Bransviceusis). The ground to the left of the gully is made 
up of displaced masses of White and Red Chalk (with a thick capping 
of Glacial Drift) which have come down over the slippery surface of 
the Speeton Clay. Some of these slips probably date back to Pre- 
glacial times, as they appear to be truly overlapped by the boulder-clay 
and gravels. These old slips form the higher portion of the slope in 
the background of the picture. Sometimes huge masses like that 
forming the terrace in the middle distance are brought down, but 
there is, besides, a constant crumbling and sliding forward of all the 
material overlying the clay, especially in wet weather, with a glacier- 
like motion, and the lower slopes are constantly " crevassed " by 
small fissures, while the likeness of the sliding masses to little 
glaciers is further borne out by the large boulder-like blocks which 
are carried forward, and by the ridge of sand and shingle sometimes 
pushed up by them where they extend to the shore. Sliding ground 
of this character is well shown in the low slope in the middle of the 
picture. The uppermost beds of the Speeton Clay, more or less dis- 
* Called " BuUtongue Nook " on the new 6-inch Ordnance Map (Sheet 
cxi.,S.W.) 
