CORRESPONDENCE. 



BOULDER-CLAY IN ESSEX, 



Sir, — Mr. Monckton regards it as improbable that anyone holds that an ice- 

 sheet can traverse hills of fine sand without denuding them. But this absurdity 

 is essential to his assertion of an East Anglian ice-sheet, for the bedding of the 

 Boulder-clay is conformable to that of the finelj'-stratified sands on which it often 

 rests. That the Glacial Drift of Essex consists largely (I quite deny the " mainly ") 

 of local material is further evidence against the said ice-sheet, and how a well- 

 stratified gravel, such as is exhibited by the pit Mr. Monckton refers to, can be 

 regarded as anything like a moraine, or due in any way to continuous ice, passes 

 my imagination. If Mr. Monckton goes to sections in Essex with a mind pre- 

 judiced by accounts of the northern drifts (which were produced by confluent ice) 

 as indicating conditions prevalent throughout West Europe, he cannot expect to 

 see evidence of marine action. Fossil evidence may be dispensed with (in the 

 Thaxted case, the shells indicate Crag, in place or nearly so). Stratification, seen 

 in every exposure worth calling a section, settles the question against ice as 

 forming the East Anglian drifts, though their material, chiefly of Lincolnshire and 

 Midland origin, indicates flotation by ice from those regions, in which there is 

 ample evidence of the action of coast ice as a powerful engine of erosion, when 

 Essex was mainly if not wholly submerged. 



Of the authors quoted, no one who knows anything of the first values his con- 

 tributions to the literature of the subject, and I wholly dissent from the conclu- 

 sions drawn from the facts recorded by the others. 



W. H. Dalton. 

 Derby Road, S. Woodford. 



Sir, — With reference to the letters of Messrs. Dalton and Monckton on the 

 above subject in the last number of the Essex Naturalist (ante, p. 109), may I 

 be permitted to submit some original observations, which although limited to a 

 small area, are probablj' typical of much to be found over the northern half of 

 Essex. 



In the railway cutting, between Braintree and Bulford stations, the Boulder- 

 Clay lies immediately on gravel and sands of "Westleton" age. The line of 

 division is very sharply drawn. There is no disturbance of the gravel or sand 

 traceable on the minutest examination, neither has either deposit entered by means 

 of a "tongue " or otherwise into the domain of the other. The inference is that 

 the deposition of Boulder-Clay came about there by a quiet process, and not under 

 the pressure and abrasion of land-ice. 



At Blewitt's pit, one mile N.E. of Stebbing village, where similar deposits 

 occur, the line of division is again sharply marked, and there is also the complete 

 absence of any disturbance of the underlymg bed. In the railway cutting, one 

 mile west of Dunmow Station, the same beds with the same phenomenon are con- 

 spicuous, and in Professor Prestwich's paper on the " Westleton Beds " (Uuart. 

 Journ. Geol. Soc. vol. xlvi.), quoting from a previous paper of Mr. Woodward's, 

 he says " the line between the undoubted pebbly gravels and the overlying 

 Glacial Drift is generally sharply defined." 



Where the Boulder-Clay rests on " Middle Glacial Gravel," the transition is 

 much less abrupt, and it is often difficult to say where the one formation leaves 



