log 



CORRESPONDENCE. 



BOULDER-CLAY IN ESSEX. 



Sir, — Referrino; to the paper "On the Boulder-clay in Essex" (Essex 

 Naturalist, vol. iv. pp. 199-201), will Mr. Monckton, or any other geologist, 

 adduce a single particle of evidence of the passage of anything resembling an ice- 

 sheet over any part of the area between Thames and Humber ? 



There are hundreds, if not thousands, of sections ampl}' disproving this 

 hypothetical :igency, and demonstrating the deposition of the Boulder-clay in 

 a berg-covered sea as clearly as that of the subjacent gravels and sands in one 

 less charged with clayey detritus. 



" An ounce of fact is worth a ton of theor)-," and the forcing of evidince into 

 harmony with conclusions drawn from observ;itions in other and entirely different 

 regions has in this matter, as in others, led to the promulgation of the most 

 contradictory ideas. 



The ice-sheet which has scored the hardest rocks of the Northern mountains, 

 under the impulse of a scarcely perceptible gradient, must be supposed in East 

 Anglia to have glided over hills of fine sand without disturbing a grain of their 

 surface ! Believe it who can ! — Yours, 



W. H. DalTON. 

 Derby Road, Woodford. 



Sir, — In reply to Mr. Dalton I should say it is unlikely that an ice-sheet 

 would move over hills of fine sand without disturbing a grain of their surface, 

 ai:d I should think it improbable that any one holds such a view. There is , 

 however, evidence to show that an ice-sheet ma}' travel over a country without 

 effecting any great alteration of the surface. (See Clement Reid, " Geology of 

 Holderness" [1885], p. 42.) 



So far as Essex is concerned, we know that, whatever the precise process may 

 have been, the surface of the ground over which the ice passed was to a large 

 extent destroyed, and the materials of the older beds re-arranged. The Glacial- 

 drift of Essex consists mainly of local material, chalk, clay, sand, and pebbles, 

 with a small pro{)ortion of foreign material intermingled, and that seems to me 

 the great difficulty which those who contend for the marine origin of this drift 

 have to meet. Thus, on the south-west of the road half-way between Ingatestone 

 and Frierning, there was last summer a pit in gravel composed of: — 



(a). Pebbles of flint, forming the bulk of the gravel and clearly derived for 

 the most part from the pebble beds, remains of which still cap the high 

 ground at Frierning Church close at hand. 

 (/>). S'jbangular flints, many. 

 (cj. Uuartz pebbles and a block of white quartz, 5 by 3^ inches. These must 



have been brought by ice from a distance. 



(d). Two large blocks of sandstone or quartzite. 



Here we find a gravel on the side of a hill mainly formeci of materials derived 



from the top of the hill. It does not look to me like a marine bed; it is not 



the least like an old sea-beach with nothing like a sea- cliff. I might give many 



more instances in support of my opinion that the Boulder-clay and Glacial- 



