408 MR. H. B. WOODWARD ON THE SOILS AND SUBSOILS OF NORFOLK. 
had been engaged for longer or shorter periods — on an average 
four years each, equal to the work of one man for about forty 
years, or at the rate of about fifty square miles a year. The results 
of this work are shown on the one-inch Geological Survey Map.* 
Summarized, the general grouping of the subsoils is as follows : — 
Formations or Subsoils. Chief Characters. 
(Alluvium ... ... ... Clay, silt, and peat. 
ecent. ( Blown Sand ... ... Loose sand. 
Pleistocene, 
iucluding 
Glacial. 
f Valley Gravel and Brickearth Gravel, loam. 
T ,,, ,, , , ,,, ) Chalky clay with stones 
Upper or Chalky Boulder Clay i , , , , 
J J ) and houlders. 
Glacial Sand and Gravel t ... Sand and gravel. 
( Contorted Drift ... ... Stony loam and marl. 
Lower Boulder Clay (Cromer ) , „ 7 , . , . _ , 
TiU j j {Only exposed m cliffs). 
Pliocene. 
' Cromer Forest Bed Series 
Norwich Crag Series 
Chalk 
Cretaceous. I Gault and Red Chalk 
Lower Greensand 
Jurassic. Kimeridge Clay 
( Only exposed in cliffs). 
) Pebhly gravel and sand 
> with shells and seams 
) of clay. 
| White limestone with 
) flints in upper part. 
Marly clay, red limestone. 
| Sand and sandstone, with 
) baud of clay. 
Clay and shale. 
That these formations have influenced the soils and agriculture 
of the county was clearly recognized by the old agricultural 
writers before the sequence of the strata was understood and 
made known. A brief account of this influence may now be 
given, dealing with the strata according to their leading litho- 
logical characters. 
The Chalk comes to the surface over considerable tracts in West 
Norfolk, from Hunstanton to Swaffham, and Thetford ; it also 
appears in places on the slopes of the Bure, Wensum, and Yare 
valleys. Less, perhaps, than any other formation in Norfolk has 
it contributed to the soil. The entire area having being overspread 
with Drift, we find patches of it here and there along the chalk 
* A reduction on a scale of an inch to four miles has been published in 
the ‘Victoria History of the Counties of England/ Norfolk, vel. i. 
t In part newer than the Chalky Boulder Clay, and in part associated with 
the Contorted Drift. 
