408 A. J. JUKES-BROWNE ON THE HESSLE 
the formation of the later clay was entirely different from that which 
obtained in the earlier period: the climate too must have been 
different ; for everything connected with the Hessle Clay points to 
conditions of much less glacial severity than those which accom- 
panied the formation of the older clay. : 
Mr. Searles Wood, indeed, deems these facts of such importance 
that he refuses to admit the newer clay as coming within the limits 
of the great Glacial Period; he refers its accumulation to a period 
of minor glaciation, which he considers as Postglacial, in the sense 
that it occurred at a time long after the epoch of major glaciation, 
to which he would restrict the term Glacial Period. 
Without altogether assenting to Mr. 8. Wood’s view of the case, 
I quite appreciate the importance of the facts to which he draws 
attention, and the reasons which have led him to adopt this break 
as the line of division between the Glacial and Postglacial Periods. 
In conjunction with Mr. Rome he drew two sections across the 
Steeping valley ; and speaking of these they write as follows* :— 
«We are thus enabled to see the relative positions of the Hessle 
clay and of the Glacial clay of mid-Lincolnshire, and the contrast 
presented by the former as a true Postglacial or valley-formed bed 
.... to the massive deposit of the latter, out of which and the 
Wold, together, the trough occupied by the Steeping river has been 
cut.... The contrast between the chalky clay and the Hessle 
clay in this section (fig. 9) 1s too distinct and complete to admit of 
the possibility of their belonging to the same formation.” 
The general accuracy of these sections, and of the conclusions 
drawn therefrom regarding the great lapse of time and the large 
amount of denudation which must have taken place in the inter- 
vening period, are fuliy confirmed by the results of my own more 
detailed examination of the country. 
The section fig. 2, on p. 405, shows how the Hessle Clay is banked 
up against the foot of the hills bounding the northern edge of the 
fenland, and also exemplifies the great difference in the relative 
positions here occupied by the two Boulder-clays ; so rapid, how- 
ever, 1s the south-westward declination of the Chalky Boulder-clay, 
that at a distance of only one mile and a half west of the line of 
section it is found at the same level as that on which the newer 
clay occurs. We are therefore led to inquire whether this is merely 
a coincidence or whether the descent of the Chalky Boulder-clay to 
to this level has been in any way connected with the limitation of 
the Hessle Clay to the eastern part of the fen-basin. 
To any one now viewing the ground there does not seem any 
reason why this latter clay should not have extended eastward 
along the fen-edge to Tattershall and the valley of the Witham. If 
the wide-spread sand and gravel which covers this district was a 
continuation of the beds underlying the Hessle Clay, some patches 
of the superimposed clay must have remained to prove its former 
existence; but nothing of the kind has been found. If it does exist 
in any part of this area, it must be subjacent to the above-mentioned 
* Quart. Journ. Geol. Soe. vol, xxiv. p. 163. 
