454 Sir E. H. Hoicorth— 



but which they admit, as do more recent explorers, pass into each 

 other. Thus they say of the most distinct of the three, the so-called 

 basement clay — a bluish or blackish, tenacious clay, forming the 

 lowest visible portion of the cliffs in Holdemess and elsewhere: — 

 " As the brown clay passes into the ash-coloured, so the latter passes 

 into the blue clay, which often occurs in patches rather than a 

 distinct bed. Indeed, all the three kinds of clay are often seen 

 banded together in one mass, but we generally find the brown clay 

 uppermost, the ash-coloured in the middle, and the blue, tenacious 

 claj' in the lowest place." (Op. cit., pp. 17, 18.) 



Mr. C. Eeid, who is disposed to postulate two Boulder-clays 

 in Holderness, separated by gravel, in some cases by fossil iferous 

 gravel, says: "It is also interesting to find that this Boulder-clay" 

 [underlying the fossiliferous gravel in one pit] " is, in its lithological 

 character, quite indistinguishable from the newer chalky and purple 

 Boulder-clay which oveidies the gravel further east." This is in the 

 valley of Croxton. He also mentions how, south of Laceby, " the 

 gravels suddenly thin out and the two Boulder-clays come together." 

 At Grimsby the sections "showed two Boulder-clays, purple and 

 chalky, and exactty alike, separated sometimes by a mere line of 

 division, sometimes by gravelly sand, in which fragments of inter- 

 Glacial shells were found. Though the sections were examined 

 almost daily, not the slightest difference could be detected between 

 the two Boulder-clays, either in their matrix or their included 

 boulders." (C. Eeid, Line, and Yorks. Surv. Mem., pp. 169, 170.) 

 This will suffice to show that, essentially, the Boulder-clays of 

 Eastern England are of one age, and graduate into each other. 

 Their peculiarities are local, due to local causes, and mark only 

 superficial differentice, and do not justify their being assigned to 

 different periods. Their difference of contents depends very largely 

 on their covering a different kind of substratum. The element and 

 factor which unites them is the presence in them all of a certain 

 number of foreign stones and debris, having, apparently, a common 

 origin, and pointing to a common explanation. 



Let us now turn to the contents of the clays, and especially 

 of the Chalky Clay. The first ingredient of these clays which is 

 noticeable is the clay itself, and I cannot help remarking that it 

 is a pity the Geological Surveyors, in the various memoirs they have 

 given us on the so-called Glacial beds, have not given us more 

 analyses of the clays. One fact seems certain, namely, that the 

 clayey matrix of these so-called Glacial clays is not an original 

 product, but a derivative one. That is to say, it was in the state 

 of clay before it was mixed with the ingredients which it now 

 contains, and was directly derived from various Secondary and 

 Tertiary clays already formed : the Speeton and other clays of 

 Yorkshire supplied the main part of the Yorkshire so-called 

 Boulder-clays-; the Kimeridge and Oxford Clays, together with 

 the variegated Reading and other Eocene beds of the Fen country, 

 supplying the clays further south. It was because these clays are 

 exposed in Eastern England, and not elsewhere, that we have the 



