Geology of Norfolk. 
469 
questions in agriculture connected with drainage and evaporation, 
' scalds/ deep and shallow ploughing, and subsoiling. 
Brick-earth of the Nar. 
I have deferred till this place the consideration of the brick- 
earth, or rather clay, of the valley of the Nar, and the fresh- water 
deposits of Gajtonthorpe, both of which appear to have preceded 
the formation of the warp, because it was necessary that the 
reader should be made acquainted with that hitherto undescribed 
member of the erratic block period, in order to understand its 
relations to these beds. 
Throughout the whole depth of the upper and lower drift, the 
thickness of which, in some of the Cromer sections, exceeds 
300 feet, no regular bed has yet been discovered containing shells 
of marine animals that had lived upon the spot. I have men- 
tioned a deposit of this kind interposed at Runton, between the 
till and the fresh-water beds at the commencement of the sub- 
mergence. The brick-earth of the valley of the Nar appears to 
have been formed towards the termination of the subsequent 
period of elevation, and to be covered only by the warp of the 
drift, which closed the erratic block epoch. This deposit is 
mentioned by Young in his report to the Board of Agriculture, 
under the name of oyster-shells and marine mud, used as a dress- 
ing for turnips, and of great efficacy on land that has been worn 
out with corn. Its fossil contents, and the area occupied by it, 
have been described by Mr. Rose in an interesting paper ' On 
the Geology of West Norfolk' in the ' Philosophical Magazine.'* 
He has traced it in brickfields, clay-pits, and wells for 9 miles 
up the valley of the Nar, with an average breadth of half a mile ; 
the most eastern point at which it has been observed being 
between Narford and Westacre. It has been named, not very 
appropriately, brick-earth, by which loam is usually understood, 
whereas it is in reality a blue clay, used in the manufacture of 
tiles and white kiln-burnt bricks. From the marine shells which 
it contains, their state of preservation, and the manner in which 
the species are grouped, it appears to have been an estuary de- 
posit. The greatest height of the undisturbed clay in the valley, 
even near its eastern extremity, does not, according to Mr. Rose's 
estimate, exceed 30 feet above the level of the sea ; but at a 
greater elevation by about 60 feet, there is in Walton Field a 
considerable accumulation of shells in sand and gravel, which 
from their broken state and the high angle at which the beds are 
inclined, appears to have constituted the beach of that inlet of 
which the clay was the deep water deposit. 
* 'London and Edinburgh Philosophical Magazine ' for 1836, vo]. vii. 
