404 MR. H. B. WOODWARD ON THE SOILS AND SUBSOILS OF NORFOLK. 
impervious nature of the surface-deposits, and by the growth of 
vegetation. 
The soil is the top covering of earth from a few inches to a foot 
or more in depth, made up most largely of the weathered subsoils, 
with an admixture of decayed animal and vegetable matter or 
humus, and with a certain amount of wind-drifted material, the 
whole acted upon in various ways by plant-growth, earthworms, 
and other organisms. 
In endeavouring to estimate the extent to which soils owe their 
mineral ingredients to the subjacent strata or subsoils, we have, in 
the first instance, to consider how far the soil may have been 
washed down slopes over the surfaces of strata with which they 
can have but a partial relationship, or, perhaps, no relationship at 
all. We have also to consider that soils are everywhere liable to 
modification, as Mr. Clement Reid has pointed out,* by the 
adventitious matter showered over the surface by winds. Stiff 
clay subsoils may also become lightened in this way, by the 
incorporation of wind-borne sand or soil which enters their 
fissured surfaces in dry weather ; and even pebbles from a thin 
gravelly soil are introduced through cracks in stiff clays three or 
four feet below ground. 
The geologist is well prepared for these phenomena, as he is 
also prepared for the occurrence of strange pebbles and pieces of 
rock which in the course of manuring have been added to the 
surface of the land. 
The depth of soil is no doubt greatly influenced by the nature 
of the subsoil. In Norfolk there are no very hard rocks, and 
except on the chalk and on the stiffer clays there is seldom any 
well-marked plane of separation between soil and subsoil. Else- 
where the mixed subsoils which characterize much of the county 
are readily weathered and broken up, and deep indigenous soils 
naturally occur in favourable situations. 
The soils of Norfolk have formed the theme of several essays. 
William Marshall, who in 1787 published two volumes on ‘The 
Rural Economy of Norfolk,’ was for two years agent to 
Sir Harbord ITarbord at Gunton. Curiously enough, he remarked 
that “ A singular uniformity of soil prevails throughout this 
county ; there is not, perhaps, an acre in it which does not come 
under the idea of a sandy loam. Its quality, however, varies 
* Geol. Mag., 1884, p. 165. 
