178 LAMPLUGH : NOTES ON THE WHITE CHALK OT YORKSHIRE. 
same feature ma)^ be observed along the marly bedding planes. In 
one instance, undir Backton, about 1| miles to the westward of the 
present section, the uppermost beds of the Lower Chalk have been 
locally crushed by the sliding forward of the massive overlying beds 
of the Middle Chalk, and an appearance of sliglit unconformability 
has tbus been produced.* Contortions are know^n to exist in the 
chalk in many places in the interior, and a careful study of these in 
connection with those of the cliff-line would probably reveal the 
presence of definite zones of pressure and movement traversing the 
whole district. 
Staple Nook evidently owes its existence to the slightly less 
resistant power of these contorted beds. A fine spring of fresh water 
rises along them and flows from the base of the cliff at low tide. 
Old Rollup, mentioned above, is the recess next beyond The Staple. 
These cliffs are, in the early summer months, the breeding place 
for vast multitudes of sea birds, chiefly guillemots ("scoots"), razor- 
bills ("auks"), kittiwakes and puffins, and the gathering of the eggs 
for sale as food has been practiced for generations by the inhabitants 
of the neighbouring villages, whose skill in the use of the climbing 
ropes is quite extraordinary. 
4. Little and Great Thornwick Cliffs. 
In this view our standpoint is the little headland on the western 
side of the recess knowai as Chatterthrow, nearly two miles to the 
eastward of Staple Nook. We look eastward across the .succession of 
ridges and inlets which nre shown from the opposite side in the next 
Plate and will .shortly be more fully discussed. 
The perforated ridge betw^een Chatterthrow and Little Thorn- 
wick is in the foreground,! that between the tw^o Thornwicks in the 
*See fig. 2, p. 10, in Mem. Geol. Survey: "Country around Driffield" 
(Sheet 94, N. W.), and nctes on section, by the writer, in "La Geologie de 
I'Est du Yorkshire," in Compte Rendu du Congres Geologique Internationale, 
Londres, 1888 , p. 154. 
t A large photograph of this headland was issued by the Society with 
their annual volume for 1882, vol. viii. I was requested to prepare the descrip- 
tion (vol. viii., p. 103) which accompanies it, but, by a misunderstanding, while 
I described a view of the eastern side of Great Thornwick (shown in pi. 6 of the 
present series) which had been taken as an alternative, the photograph actually 
issued was afterwards substituted, so that in some points the description was 
quite inapplicable. 
