BOTJLDER-CLATS OF LINCOLNSHIRE. 1 27 



The junction here is level, and no signs of erosion are visible. 

 Purther, in another brickyard south of the town, a similar reddish 

 clay passes downward into purple-brown clay without any kind of 

 separation. 



I also found the same complete passage from one kind of clay 

 into the other, shown in a brickyard at Ludborough ; the section 

 here was : — 



feet. 



Clean, stiff, loamy clay , 2 



Stratified sand, with layers of loam 5 



Eedclish-bi'own clay with grey streaks, passing down into 

 puvple-brown clay with bluish streaks and then into 

 uniform bluish-brown clay 13 



At Cleethorpes, where Mr. Searles Wood himself says that the 

 Purple Clay is seen capped with Hessle Clay along the cliffs, the 

 appearances are in reality similar to those above described at Lud- 

 borough. Near the steps which lead down on to the shore the cliff 

 is about 30 feet high ; at its base there is about 7 feet of purplish 

 clay passing upward into hard reddish clay streaked and mottled with 

 light grey ; along the horizon of passage there is an appearance of 

 stratification, but no well-marked line of division. The whole 

 forms one solid mass traversed by the same planes of jointing or 

 fracture. 



"When traced in either direction, small lenticular beds of yellow 

 sand may be found, some distinctly within the limits of the reddish 

 clay, some about the horizon of passage, but all of them discon- 

 tinuous. 



I may add that my colleagues, Messrs. Reid and Strahan, agree 

 with me as regards the complete passage from one clay to the other 

 at Cleethorpes. 



I have not personally visited the Holderness-coast sections ; but 

 Mr. Lamplugh, who studied them closely and continuously for some 

 years, informs me that there is nothing which exactly corresponds 

 to Mr. S. Wood's representation of the Hessle Clay, " though there is 

 an uppermost Boulder-clay, generally reddish brown in colour, 

 which may be traced for miles along the coast." This reddish clay, 

 however, is as well developed to the north of Flamborough Head as 

 it is to the south of that point ; while the Hessle Clay, as defined 

 by Mr. S. Wood, does not reach so far northward as Bridlington. 



In a recent letter to me, Mr. Lamplugh says : — " I do not believe 

 in any important unconformity between this clay and the beds 

 below it, and the more I see of our glacial sections, the more dis- 

 inclined am I to believe in any great break in the sequence of 

 events. The best-marked unconformity that I know of is at the 

 base of the Purple Clay in this neighbourhood [Bridlington] ; but 

 at Dimlington even this break is not nearly so clear." 



This line of erosion did not escape Mr. S. Wood ; he says that the 

 basement clay " is overlapped in every direction by another thick 

 bed of Boulder-clay, to which, in most of its exposures, it presents 

 a very denuded surface, rising up beneath it in bosses, and in some 



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