MaiD — Drift Deposits of the Eastern Counties. 277 



equivalents of Ms Middle drift. Moreover, this Middle drift is 

 nothing but a mass of sand and gravel of constantly varying 

 character, and having by itself no distinctive aspect. 



I wish to explain that in referring to the general uniform altitude 

 of the bed I termed "high-level Boulder-clay" (Mr. Wood's_ Upper 

 drift), I did not suppose that this was any distinctive test of its age, 

 as the original irregular basement line upon which it was deposited 

 would to a certain extent determine its altitude ; indeed, there are, 

 I believe, several isolated patches in the neighbourhood of Tunstall, 

 Chillesford, etc., at a much lower level than the general mass foiming 

 the higher ground of Suffolk ; but whilst a? deposit having a great 

 range of altitude mmj extend down to any point towards the sea- 

 level, a uniform limitation of height (which is, I believe, the case 

 with most of the Boulder-clays on the coast-line) may result from 

 having been deposited by an agency that never attained beyond a 

 certain level, and may therefore, in one sense, be taken as a distinctive 

 test of age. 



The clay which extends so widely over High Suffolk to an altitude 

 of from two hundred to three hundred feet above the sea, never 

 attains anything like this height in any coast section, and as you 

 descend from the flat table-land it appears to be abruptly cut off by 

 the general denudation-contour of the country. 



The general level of the Chalk-surface in Suffolk is from eighty to 

 one hundred feet above the sea, and on Mr. Wood's classification his 

 Lower drift occurring on the coast, would have formed with the 

 Chalk a tolerably level basement line for the future superposition of 

 his Middle and Upper drifts. How is it, then, that the clay on the 

 high ground of Suffolk, which is so uniform in level and mass for 

 many miles inland, disappears (or, on Mr. Wood's view, becomes 

 attenuated) as the lower ground is reached ? I believe it is only to 

 be accounted for by the denudation of the clay on the higher level 

 previous to the deposition, as a sort of fringing terrace, of that on 

 the coast, which throughout the whole circuit of the country never, 

 on the coast, attains the height of the inland drifts. If it is a mere 

 extension, coastwise, of the drifts occurring at higher levels, the 

 lower level of the base at the coast on which it was deposited would 

 account for it ; but the coast Boulder-clay and drifts frequently occur 

 where the higher ground, as you recede from the sea, is driftless. 

 If this coast-clay is as Mr. Wood supposes, a more ancient deposit 

 than the higher drifts occurring inland, it seems difficult to account 

 for the higher drifts which were deposited within- a few miles inland 

 on the Chalk, not being also superimposed on the coast-drifts — the 

 surface of which would have formed a foundation of about the same 

 height as the inland Chalk. 



Again, if it is assumed that the high-level Boulder-clay and 

 subjacent gravel-beds (Mr. Wood's Upper and Middle drifts) form 

 a portion of the cliffs on the Norfolk coast, descending towards the 

 coast on a sloping base line, why should they become so attenuated in 

 mass as in no instance to attain, with Mr. Wood's Lower drift, a 

 collective thickness greater than that without the so-called Lower 



