CRETACEOUS SERIES IN LINCOLNSHIRE AND YORKSHIRE. 333 



slipped down, I think, within this century, and the debris entirely 

 obscures for some distance all traces of the lower beds. The site of 

 this slip is now planted with trees, but it still bears the name of 

 " Earthquake " plantation. A slip of minor importance took place 

 at Leavening within living memory (see p. 341). It is without the 

 province of this paper to discuss at greater length the question of 

 the weathering of the Chalk-escarpment of Yorkshire, my object 

 being to show that little dependence should be placed on the posi- 

 tion of small exposures (mere patches frequently) as indicating the 

 original outcrop of the beds. 



It is, indeed, quite possible that the surface on which the Cre- 

 taceous rocks rest is not a perfectly level one, and that features de- 

 veloped during the period of time represented by the unconformity 

 may interfere with the regularity of the base-line of the Chalk ; but 

 I cannot help thinking that the irregularity of this base-line has 

 been exaggerated, and is due in a large degree to the displacement 

 of the Chalk itself ; nor can much dependence be placed on estimates 

 of the thickness of the Lower Chalk which are based on the position 

 of the outcrop of certain beds in relation to the contour-lines. 



Part of the Chalk escarpment of Wiltshire south and east of 

 Swindon seems to present similar features, according to the diagram 

 and description given in the Survey Memoir (Expl. of Sheet 34, 

 pp. 33 and 34). In that district large masses of Chalk and Upper 

 Greensand seem to have slipped and foundered down the steep slope, 

 so that " the boundary of the Chalk and the Upper Greensand is 

 generally completely obscured." 



The undercliif of the Isle of "Wight may be also quoted as an 

 analogous case on a more extended scale. 



(A.) The Red ChaXk or Hunstanton Limestone, 



Entering Yorkshire from the south, the Eed Chalk is first seen at 

 Welton Springs ; to the north of this, though giving ample evidence 

 of its presence near the base or higher on the brow of the Wold, 

 there is no exposure where a satisfactory section can be seen between 

 the Humber and the well-known cuttings on the Hull, Barnsley, 

 and West Riding Junction Railway, more iiian a mile east of the 

 station at South Cave. 



The best section of the Red Chalk is to be found in the cuttings 

 between the two short tunnels, the one at Weedly Springs and the 

 other under Sugar Loaf Hill. Here it is seen to be about 7 feet 

 thick, and is of a grey colour in the centre. Belemnites minimus 

 occurs commonly. It may be said to rest on Kimmeridge (?) Clay; 

 but between it and this formation can be seen at intervals a thin 

 layer of yellowish, very fine sandy material, containing roundish 

 concretionary nodules of ironstone, which show, when broken, a 

 slightly oolitic structure ; but there seems to be hardly any coarse 

 quartz or other mineral fragments in it, and in the Red Chalk itself, 

 whose base partakes of the character of this yellowish material, 



