The Chalky and other Clays of Eastern England. 451 



that the ingredients of the Boulder-clay are, for the most part, 

 supplied by rocks, upon or near which it reposes. That this is 

 actually the case, and not an accident of colour, is further attested 

 by the included fossils; Gryphcea dilatata and Belemnites Owenii, 

 for example, are abundant upon the Oxford Clay, and Ostrma 

 deltoidea upon the Kimmeridge Clay." (Skertchly, communication 

 to Geikie's " Great Ice Age," new ed., p. 346.) 



It is curious that those writers who have been most ready to 

 concede this change in the Chalky Clay, in accordance with its 

 substratum, have not gone a step further, and also seen that the 

 chalky character itself of the clay in certain districts is simply 

 due to its being upon, or in close proximity to, the Chalk in situ, 

 and that there is no justification for constituting the Chalky Clay 

 a separate horizon. It is because the Chalk occupies so much of 

 the area, and is itself so easily disintegrated, that the name 

 Chalky Clay, rather than Oolitic Clay or Liassic Clay, has been 

 not improperly given to it. 



That this feature of the Chalky Clay is due entirely to its lying 

 upon or close to chalk, is also proved by another feature of its 

 distribution, which is intei'esting for more than one reason, and 

 which has not been sufficiently noticed. In the first place, the 

 Chalky Clay is, so far as I know, largely confined to Eastern 

 England, and is found nowhere else in the world, pointing to 

 there not being the actual conditions elsewhere which prevail 

 here. But this is not all. Mr. Searles Wood, jun., once published 

 a little map roughly defining the area in which it occurs. A larger 

 and more detailed map is appended to a manuscript memoir of 

 his in the possession of the Geological Society, but it has only 

 been since the detailed plotting and mapping of this area by the 

 Geological Survey that it has been possible to define its frontiers, 

 and it would be very useful to us all if the results thus obtained 

 were set out on a map of moderate dimensions. 



It will be seen that the distribution of the Chalky Clay, when 

 thus viewed as a whole, is very remarkable. In the first place, it 

 is entirely an inland deposit with duly circumscribed limits and 

 boundaries. It really occurs in several detached masses — two of 

 them in Lincolnshire, one in Yorkshire of no great importance, 

 and a fourth covering more or less an area of sevei'al hundred square 

 miles round the depression of the Fens. 



In each case the area occupied by the Clay is an insular area, 

 separated from the sea by other surface beds. At one point only — 

 and this is clearly accidental, and due to the recent cutting back 

 of the coast — does the Chalky Clay look down on the sea. In 

 Lincolnshire it is only found to the west of the Lincolnshire 

 Wolds ; while in its great homeland further south it is separated 

 from the sea on all sides by beds of Crag and of so-called contorted 

 beds — Middle Glacial beds, etc. This is the case all round the 

 coasts of Norfolk, Suffolk, and Essex, and in the low-lying northern 

 frontier of the marshes and peat-lands of the Wash. To the south 

 it thins out, and virtually ends with the hills bordering the Thames 



