Geology of Norfolk. 
All 
position to the till is therefore incomplete. It may, however, 
be inferred from the fact that till has been found underlvins the 
alluvial deposits in deep excavations in the marshes. 
Freshwater Deposits of Gaytonthorpc. 
About 2 miles north of the ancient estuary of the Nar there is 
a small parallel valley, also opening; to the Wash. In this valley, 
and a quarter of a mile north of Gaytonthorpe, a blue clay, con- 
taining lumps of waterworn chalk, and abounding with small crys- 
tals of sulphate of lime, is worked for brick-making. No shells 
have yet been found in it, and in their absence it is doubtful whe- 
ther it is a form of till or an estuary deposit like that of the Nar. 
About half a mile east of this brick-field clay has been formerly 
dug for agricultural purposes on the farm of Gaytonthorpe Hall, 
on the north side of the road, but the pit is now full of water. 
On the south side of the road is another pit at a higher level, still 
worked. In this pit several beds of clay and calcareous sand rest 
upon an irregular surface of a bed resembling in composition the 
more chalky varieties of till. The surface soil consists of a loamy 
warp, containing in some parts accumulations of flints of consider- 
able size, and filling furrows and pipes deeply excavated in the 
calcareous sand and associated clay. The depth and extent of 
the several beds will be understood from the accompanying sec- 
tion (Section X.), which is constructed on the same vertical and 
horizontal scale, namely, 20 feet to 1 inch. From the spot where 
bones " is written on the section, Mr. Rose has obtained a nearly 
complete set of the teeth of the lower jaw of a species of hos. 
From the numerous fragments of a very thin univalve in the 
calcareous sand, accompanied by homy opercula, resembling those 
of a small paludina, and from part of a unio occurring in one of 
the beds of clay, I was satisfied that they were freshwater deposits. 
The specimens which I procured were too imperfect to enable me 
to obtain an opinion on them from an eminent naturalist ; but jVIr. 
Rose, who conducted me to the pit, and who was at first reluctant 
to believe them fluviatile, has recently set the question at rest by 
the discovery of several entire specimens of cyclas and one plan- 
orhis. Though the species are not yet determined, there can be 
no mistake about the presence of these freshwater genera. We 
maj", therefore, conclude, that whatever were the causes which 
produced the Marp, they were not in operation until the latter 
portion of the period of elevation, when the marine strata which 
had accumulated upon a terrestrial surface submerged to the ex- 
tent of GOO feet at least, had been again laid dry, and had conti- 
nued a terrestrial surface for a sufficient time to permit a consi- 
derable accumulation of freshwater strata near the head of a 
valley which was filled perhaps in its lower part with an estuary 
