Geoloyy of Norfolk. 
465 
tion of the agencies which produced this difference I shall not 
discuss in these pages. 
4. The marine deposit thus formed was again laid dry. Dur- 
ing its elevation valleys were excavated in it, and over large areas 
the upper drift was stripped off with the exception of some de- 
tached masses. The change in the relative level of the land and 
sea during these operations must in Norfolk have exceeded 600 
feet, for the forest on the Cromer coast is partly below, very little 
above the sea, and the highest parts of the watershed are covered 
with the upper drift,* 
5. Warj) of the Drift. 
Over the denuded surface of the upper drift and of the lower 
drift, when the denudation has extended so low, another deposit 
has been thrown down, which has hitherto been little noticed, or 
has been passed over in the descriptions of geological sections 
under the name of vegetable mould. It appears to have been a 
deposit from turbid waters returning to a state of tranquillity. I 
have named it provisionally the warp of the drift, a name which 
is, however, not altogether appropriate, because, though in low 
situations, and on level surfaces, it resembles the warp or sedi- 
ment left by the tidal waters of muddy estuaries, and is scarcely 
distinguishable from modern alluvial deposits ; yet in other situ- 
ations, far above the reach of existing streams, stones of consider- 
able size (in Norfolk chiefly flints) are contained in it, and in 
the vicinity of mountain-chains, the large blocks or boulders 
which either strew the surface or are enveloped in this deposit 
appear to have been dispersed at the period of its formation. 
Its history is yet to be discovered. For some time after it had 
attracted my attention I regarded it as the deposit left by the 
waters under which the drift was formed, as they gradually retired 
during the upheaval and desiccation of the land ; but in the 
course of my observations in Norfolk, I have met with indications 
of the denuded surface of the drift having become dry land before 
this warp was spread over it. 
The point, however, which most concerns our present inquiry 
is, that the varieties of soil depend principally on the depth and 
composition of this deposit, while these again depend on the form 
* Captain Robe, in reply to inquiries made by Mr. Rose, gave these as a 
rude estimate of the heights of the following points : — Docking, 600 to 650 
feet ; SwafFham, 450 ; Great Massingham, 600 ; adding that the triangu- 
lation of Norfolk was performed with instruments too small to be depended 
upon for the vertical angles; and that without accurate instruments it 
would be impossible to class the ranges according to their relative alti- 
tudes, those altitudes differing so little among themselves. See Mr. Rose's 
paper in the Phil. Mag. 
