Witham Whitaker—The Red Chalk of Norfolk. Ps 
because it comes on where the latter has thinned out, the one being 
replaced by the other, might be just as well put forward in favour 
of the theory that Red Chalk represents the Chalk Marl—even more 
strongly, for the vanishing points of these two are nearer than those 
of the Gault and of the Red Chalk. 
It was the absence of these two clayey beds in the north-western 
corner of Norfolk that led me to think of the possibility of the Red 
Chalk being a colour-line rather than a bed, and I am not yet sure 
that this absence may not have something to do with the red colour 
that co-exists with it. The Chalk Marl stops the infiltration of water 
downwards through the Chalk, of which there is good evidence in 
the springs thrown out at the outcrop of the former; whilst the 
Gault would stop any upward rise of water that might occur through 
the underlying sands, under different physical conditions from those 
Wwe now see, shutting the water up in those sands, as in deep wells 
through Gault to Lower Greensand. It is quite possible, therefore, 
that the absence of these clayey beds may have something to do with 
the presence of that redness, which is owing perhaps to the per- 
oxidation of some salt of iron, a process that would be made more 
easy by freedom of percolation by water. 
Though perhaps beyond our subject, I may notice another bed of 
clay, which differs from the two just noticed in being peculiar to 
our district—I mean the bed that occurs in the Neocomian Sands 
(towards their upper part) from Hunstanton southwards to Flitcham, 
first noticed I believe by Mr. J. H. Teall! whose essay gives the 
best account of the Norfolk Neocomian that we have. It is perhaps, 
the presence of this bed which has caused the formation of the 
Carstone, a stone which is merely a sand or grit cemented by brown 
iron-oxide; at all events the Carstone is best developed where this 
clay exists and where the Chalk Marl and Gault are absent, whilst 
elsewhere it ceases to exist as a marked bed. The clay seems to 
have stopped any further sinking of water with iron-salt in solution, 
and to have held it in the upper part of the sands. It should be 
noted too that it is in the same district that our Red Chalk occurs, 
and thus, whilst in that district ferruginous water could sink no 
great way below the horizon of the Red Chalk, but could easily go 
thus far, a little to the south, where Chalk Marl comes in, no such 
water could get to that horizon at all. 
Having just travelled geologically a little way from our subject 
I will now, for a short time, take you away from our district. As 
you know, Red Chalk is not confined to Norfolk ; occurring also, 
and to a greater extent, in Lincolnshire and Yorkshire. But we 
find in those counties that there is not simply one Red Chalk, but 
another, and a thicker, bed comes on many feet up in the Chalk. 
This upper red bed must therefore belong to the Chalk, and, on the 
supposition that the lower bed does not, we are faced with the 
strange anomaly of two members of the Cretaceous Series, elsewhere 
distinct, putting on together the same exceptional character. I do 
1 The Potton and Wicken ae ape Deposits, pp. 16 —28. 8vo. Cambridge and 
London, 1875. 
