410 A. J. JUKES-BROWNE ON THE HESSLE 
Regarding the origin of the materials composing it in the north 
of the county, Messrs. Wood and Rome remark * that ‘the colour 
of the Hessle clay, coupled with the presence of the chalk fragments 
and the boulders in question, seems to show that it has been mainly 
formed, and its boulders derived, from the degradation of the purple 
clay, an admixture of material having been introduced from the 
chalk which had been laid bare of the Glacial clay during the previous 
early Postglacial denudation.” 
All along the eastern slope of the Chalk Wolds, where it may be 
supposed that the Purple Clay lies underneath, it would appear 
that the Hessle Clay preserves much the same colour and character ; 
but on reaching the south end of the Wolds and crossing the line 
along which their scarp must be prolonged as an underground ridge 
stretching south-eastwards, we find near Burgh a very chalky 
Boulder-clay ; and whether this belongs to the Purple or to the 
Hessle Clay, I am disposed to attribute its chalkiness to the proxi- 
mity of the chalk-ridge below. 
Moreover, when we are well within the strike of the Neocomian 
series (clays between thick sandstones), we find that the Hessle Clay 
puts on a loamy and sandy facies, and that its landward border is 
actually fringed with sandbanks for some distance. Traced south- 
ward to Stickney, it becomes a stiffer and more sticky clay, though 
still brownish in colour and charged with pebbles of chalk; here it 
appears to rest on the Kimmeridge Clay, and further south on Upper 
Glacial Clay of the dark blue colour which it usually presents in 
this part of the Fenland. 
It may have been noticed that in speaking of the clay underlying 
Boston, which may be part of the Hessle Clay, Mr. Skertchly 
described it as dark blue in colour ; now it is possible that it may 
have acquired this tint from the erosion of the underlying blue clays, 
just as further north it appears to take its colour from the Purple 
Clay. Whether this be the case or not, there is sufficient evidence to 
show that the colour, character, and constitution of the Hessle Clay 
are influenced by the nature of the rock beds which underlie it—not, 
however, after the fashion described by Messrs Tiddeman and 
Skertchly, where a Boulder-clay derives its colour and character from 
the rocks over which it has been pushed ~; the Hessle Clay, on the 
contrary, seems to exhibit the phenomena we might expect on the 
supposition that it was formed against a shore-line by the combined 
action of sea-waves and coast-ice. 
I am aware that Dr. James Geikie takes an entirely different 
view; but his arguments are principally founded upon the supposi- 
tion that the Hessle Clay behaves in the same manner as the older 
Boulder-clays. He asserts, in direct opposition to Mr. 8. V. Wood’s 
opinion, that “ the Hessle boulder-clay yields no proof of a marine 
* Quart. Journ. Geol. Soc. vol. xxiv. p. 151. 
t Quart. Journ. Geol. Soc. vol. xxviii. p. 484, ‘Great Ice Age,’ p. 358. I may 
here remark, however, that this is no proof of the terrestrial origin of such 
Boulder- Clay ; coast-ice breaking up, and drifting in a strong current would 
leave a similar trail of rock-débris and differently constituted clays. 
