12 THE NEW RAILWAY BETWEEN UPMINSTER AND ROMFORD. 



high and low ground alike, being found from the top of the Chalk 

 escarpment down to points not greatly above the level of the sea." 



I may illustrate this statement by the following case. In the 

 valley of the Stort, about Sawbridgeworth, we find the Boulder 

 Clay forming the plateau on each side, and lower beds of Glacial 

 age exposed in the valley itself. Crossing the plateau in an easterly 

 direction, we come to the valley of the Chelmer, two or three miles 

 north of Chelmsford, in which lower Glacial Beds are also visible. 

 But, whereas the level of the Boulder Clay plateau about Saw- 

 bridgeworth is between 200 and 300 feet, on the Chelmer, near 

 Broomfield, it is between 100 and 200 feet, averaging nearly 100 feet 

 less. And, in addition to examples of this broad and general kind, 

 many might be brought forward illustrating the local variations of 

 small patches. In the Geological Survey Memoir on the Geology of 

 the Neighbourhood of Colchester, by Mr. W. H. Dalton, it is stated 

 that " between East Thorpe and Birch " (villages about two miles 

 apart) " the Boulder Clay lies in a hollow, either denuded in, or 

 formed by, the irregular deposition of the gravel.'' Now this hollow 

 appears to have no connection with any existing system of drainage. 



Many examples might be given, showing the very varied height 

 of the outlying patches of Boulder Clay found on or near the course 

 of a straight line drawn from Maldon to Brentwood : but it seems 

 unnecessary to do more than to allude to them, without attempting 

 to describe them in detail. 



It may be useful, in conclusion, to give a brief summary of the 

 leading points in what I have written on this Hornchurch Boulder 

 Clay and the Thames Valley Beds. 



In the first place, the discovery of the Boulder Clay beneath the 

 highest and oldest gravel terrace of the Thames valley system, 

 justifies the remarks made in a previous communication to the 

 Essex Field Club, as to the rashness of assuming that evidence of 

 the action of ice in some form is equivalent to evidence that the 

 deposit showing it dates from the Glacial Period. For if the Boulder 

 Clay is older than the Hornchurch gravel, it must be still more 

 ancient than the river deposits south of Upminster, or those of Erith, 

 Crayford, Ilford, or Grays. Secondly, the beds in which the Mam- 

 moth remains were found at Endsleigh Street seem to me to be simply 

 River Drift, of more recent date than the Hornchurch gravel ; and 

 the Mammoth there, as at Erith, Crayford, Ilford, or Cirays, to be 

 in strata rightly termed post-Glacial, or, in other words, of later 



