456 
Geology of Norfolk. 
posits, varies in depth from less than six inches to more than five 
teet ; and its depth is dependent on the contour of the surface, 
which is itself a result of denudation. 
5. It is frequently found resting upon rocks of all ages, without 
the intervention of any other member of the drift. 
6. Its depth in such cases is equally dependent on contours 
which are the result of the denudation of those older formations 
effected in part during the submergence of the erratic block 
period, and in part durmg antecedent geological epochs. 
In order to generalise the phenomena of the variations of soil, I 
knew that it was necessary to lay down those variations on a map 
exhibiting accurately, and on a large scale, the physical features 
of the district. Stimulated, therefore, by the importance of the 
problems, both in pure and applied geology, of which Norfolk 
appeared to offer the key, I did not hesitate to expend the fifty 
pounds, which was the utmost the Journal Committee felt justified 
in allotting to these objects, in traversing the county for the pur- 
pose of laying down the variations of soil upon the Ordnance map ; 
although it was expressly stipulated, on the part of the Royal 
Agricultural Society, that they %vould not engage in a survey, and 
although Young has stated of the agricultural map appended to 
his Report of Norfolk, that he had l)een obliged to travel many 
hundreds of miles to give it as much accuracy as such a sketch 
was susceptible of, short of that which would have required years 
rather than months for its completion. 
On commencing this work in the vicinity of Norwich, I found 
the variations of soil so sudden, so frequent, and apparently so ar- 
bitrary, that I almost despaired of reducing tliem to any law. I 
therefore repaired to the cliffs of Cromer for the purpose of study- 
ing the order of succession there exhibited, and the sequence of 
events indicated by it. Up to this period I had been impressed 
with the belief that there was little or no regularity in the de- 
posits of the erratic block period ; that they had either been 
formed by the violent and transient action of the sea, bursting in 
waves over the surface of the land, or that, if formed on a perma- 
nently submerged surface, the boulder clay had been dropped at 
random, in detached masses, from floating icebergs, among sand 
and gravel. I found, by the aid of the coast and river sections, 
that the upper and lower strata of the drift are distinct formations, 
differing in their characters, and continuous over areas as exten- 
sive as many of those occupied by the tertiary strata; possessing, 
in common with them, appearances which could only have re- 
sulted from gradual accumulation ; while those by which they are 
distinguished from all other sea-born strata appear capable of a 
satisfactory explanation by the prevalence, during the epoch of 
