402 MR. H. B. WOODWARD ON THE SOILS AND SUBSOILS OF NORFOLK. 
however, have so changed with the increased cost of labour and 
the introduction of artificial manures, that there is more need 
than ever of the union of science with practice. 
To gather the full information suggested by modern research 
even over the limits of a parish would involve, perhaps, more 
expense than the landowners and farmers might be disposed 
to defray. Detailed investigations of soils and subsoils have, 
however, been carried on with State aid in Germany, in the 
United States, and elsewhere; while in England, apart from the 
important personally-conducted experiments of Gilbert and Lawes 
on the influence of manures on particular soils and crops, special 
studies of soils have been commenced at the Reading College 
under the direction of Mr. Douglas A. Gilchrist.* 
Perhaps the most serious question is the number of observations 
necessary to give a fair notion of the quality of the soil. In some 
localities the soil varies much within the space of one field. It 
may, therefore, be useful to review the relationship between soil 
and subsoil, with especial reference to Norfolk; for if soils are 
mainly dependent on the subsoils, a geological map, on which these 
are depicted with the highest possible accuracy, should serve as 
a basis for soil investigation. Moreover, the conditions under 
which soils were accumulated is a subject which rightly comes 
within the purview of the geologist. 
Strictly speaking, the subsoil is the geological formation which 
lies immediately beneath the soil, although the term has sometimes 
been restricted to the weathered and disintegrated portions of the 
subjacent rock. This restriction cannot, however, be maintained. 
On the chalk formation, for instance, the soil is sometimes 
exceedingly thin ; a ploughed field may look brown and loamy, 
but an adjacent chalk-pit may show but a few inches, or hardly 
a perceptible trace of soil. In such instances the chalk is clearly 
the subsoil. On stiff clays again there is often but a skimming 
of soil. This is the case in areas of London Clay, and it may be 
experienced in some London gardens Avhere London Clay is 
distinctly the subsoil. On such formations the purely indigenous 
soil is apt to be thin ; but everywhere the thickness of soil depends 
very much on the physical features, for in heavy rain the soil on 
sloping arable lands may be partially washed downhill, the streams 
are rendered turbid, and a film of sediment may be spread over 
# A First Report on the Soils of Dorset was issued in 1899. 
