Geology of Norfolk. 
447 
little knowledge of either agriculture, chemistry, or geology, are 
putting themselves forward as their expounders, and are expound- 
ing them in a manner not very likely to bring science into repute 
with practical men. 
The laws which regulate the distribution of soils constitute a 
more complicated problem than is usually supposed. In the 
agricultural application of geology, we must remember the ex- 
istence of the loose covering of detrital matter as well as the 
regular alternations of the stratified beds and irregular intrusive 
masses of unstratified rocks ; and we must not fall into the error 
of exaggerating the agricultural influence of the two latter, be- 
ca.use the former is excluded from our geological maps, which 
only exhibit the solid rock nearest to the surface. The detrital 
deposits, from their superficial position and their almost uni- 
versal distribution, are of the most importance to the farmer. 
They not unfrequently attain a depth of several hundred feet, 
producing a class of soils in which the agricultural influence of 
the subjacent solid rocks is reduced to its minimum ; and when, 
on the other hand, they do not exceed a depth of two feet, and 
that influence approaches its maximum, they include not only the 
soil turned over by the plough, but the subsoil, in the strictly 
agricultural sense of the term. In those cases in which they are 
the thinnest they always modify considerably the characters of the 
soil derived from the subjacent solid strata, and in those cases in 
which the detrital deposits attain their greatest development, the 
solid strata still exercise some influence, partly by the inter- 
mixture of their fragments in the surface soil with others trans- 
ported from a distance, and partly by the beds of clay, marl, &c., 
derived from their ruins, and buried at greater but still accessible 
depths, where they furnish, to those who will seek for and use 
them, the means of correcting chemical and mechanical defects 
in the composition of the soil and subsoil. No agricultural maps, 
therefore, such as those appended to the Reports of the Board of 
Agriculture, which only exhibit, and that imperfectly and on a 
very small scale, the variations of the surface, and neglect those 
of the substrata contained in the detrital deposits and in the still 
deeper solid strata, nor geological maps from which those detrital 
deposits, except in a few extraordinary cases, are excluded, can 
exhibit the true agricultural relations either of an extensive dis- 
trict or a single estate. 
Norfolk affords a striking illustration of these truths. Well 
defined by natural boundaries, the Ocean, the Waveney, the little 
Ouze, and the Ncn, it forms only part of a large geological dis- 
trict, in which the superficial deposits, from their extensive de- 
velopment, assume an important agricultural character. With 
some interruptions from the alluvial tracts of the Humber, the 
