THE Nf:\V RAILWAY BETWEEN UPMINSTER AND ROMFORD. II 



• 



case the Boulder Clay ended a short distance northward of the 

 edge of the River Drift, and the probable relations of the two 

 formations could be but matter for speculation. The most southerly 

 point at which the Boulder Clay appears at the surface, in the 

 Romford district, is at Maylands, about three miles north of the 

 Hornchurch cutting. And it is noticeable that at Maylands the 

 Boulder Clay comes down to a level considerably below the 200 

 feet contour-line, though almost all of it, in the immediate dis- 

 trict, lies above that height. It was, therefore, suggested during 

 the discussion on my paper at the Geological Society last March, 

 that the Hornchurch Boulder Clay, being at a level still lower than 

 that at Maylands, pointed towards the probability of the pre-Glaciai 

 age of the Thames valley system. But this is, I think, to exaggerate 

 greatly the significance of the low level of the Boulder Clay at 

 Hornchurch. All that it really does tend to show is, that there 

 once was probably a hollow or valley parallel with that of the Ingre- 

 bourne, having a direction from north to south, or nearly at right 

 angles to that of the present course of the Thames, and that the 

 Boulder Clay more or less occupied this hollow. There may have 

 been at the time a valley to some extent coincident, here and there, 

 with that of the present Thames ; but its deposits remain unknown 

 to us."' Of those which we find in the present valley system, the 

 oldest terrace — as we are entitled to assume that at Hornchurch to 

 be, in the absence of special evidence to the contrary — is manifestly 

 post-Glacial in the sense of being later in date than the Chalky 

 Boulder Clay. And this, as I have already remarked, seems to me 

 the only sense in which the term can rightly be used in south-eastern 

 England. 



I have said that we may easily exaggerate the significance of the 

 low level of the Boulder Clay at Hornchurch. Where, as in northern 

 Essex, we see Boulder Clay forming a continuous plateau ; or one 

 the continuity of which is broken only by the valleys of streams in 

 which lower beds are exposed, we find the base of the Boulder Clay 

 at the most various levels. In the Geological Survey Memoir, 

 on Sheet 47 (which includes north-western Essex with portions of 

 adjacent counties), we find the following general statement : — " It 

 is evident the clay was not formed in fragments as mapped, but in 

 one continuous sheet. It has been cut through in post-Glacial 

 time by the present valleys ; but, with this exception, it spreads over 



5 See Notes at end of paper. 



