Geology of Norfolk. 
455 
sheep-walks and rabbit-warrens, declared by one of them to be 
the best purpose to which they could be applied, are alike mem- 
bers of the drift. 
The questions, therefore, of which I proposed to myself the 
solution were the following : — 
1. The laws which regulate the distribution of soils under the 
combined influence of the solid strata and the drift. 
2, The geological relations of the marl and clay which have 
effected so great a revolution in the cultivation of Norfolk, whe- 
ther they are peculiar to that county, or whether the landowners 
of other parts of England may e.xpect to find on their estates 
similar means of improvement. 
3, Whether the structure and composition of the soil and sub- 
strata of Norfolk would suggest any improvement in the esta- 
blished practice of that district. 
4. The attempt to solve these practical problems could not fail 
to throw some light on that part of geology which is at present 
the most obscure, namely, the history of the deposits which im- 
mediately preceded the present condition of the earth, and the 
agencies which impressed upon them their peculiar characters. 
In all these inquiries I trust I have accomplished something; 
but in this paper I shall confine myself to the two former. The 
third will be made the subject of a future communication. The 
last would be out of place in the pages of this Journal, and will 
be only adverted to so far as is necessary for the elucidation of the 
laws regulating the distribution of soils. 
These laws may be thus stated : — 
1. The deposits of the erratic block group indicate, in England-, 
a long period occupied in their formation upon a terrestrial sur- 
face gradually submerged, and in their denudation during gra- 
dual re-elevation ; the whole period being characterised by 
peculiar agencies which distinguish it from the long series of 
the secondary and tertiary groups which preceded, and from 
the modern or alluvial deposits which succeeded and are still in 
progress. 
2. The variations of soil, in districts thickly overspread with 
di'ift, depend upon the amount of this denudation, which has in 
some instances caused the lower beds of the erratic block group, 
of different composition from the upper beds, to be the strata 
nearest to the surface. 
3. The effects resulting from this cause have been modified by 
a deposit hitherto little noticed, which closed the erratic block 
period, and which has been spread unconformably over the de- 
nuded surface of the earlier members of that group. 
4. This latest deposit, which shades off into the alluvial de- 
