134 The Agricultural Relations of the Western Portion 
an accurate knowledge of the constituents of each is very de- 
sirable. In practice, two kinds of these marls are recognised in 
the neighbourhood of the Forest — "shell-marl" and "cherry- 
marl." The former consists of clay, rendered calcareous by the 
presence of shells, whole or only slightly broken. In the cherry- 
marl the argillaceous and calcareous matters are more intimately 
blended, and the latter consists of shells very finely comminuted. 
Its local name originated in some red streaks of oxide of iron, 
which are often present in it. 
Much difference of opinion exists as to the relative merits of 
these two varieties as a manure. Tlie prevalent feeling appears 
to be, that the cherry-marl lasts the longest, but that the shell- 
marl produces the earliest effects. From the bones of mammals 
and reptiles which have been found in some of the beds, I 
thought it probable that some of thern might contain phosphates, 
and others not. Under this impression I submitted some of the 
specimens of the favourite cherry-marl to the examination of 
Dr. Playfair ; but he found nothing to justify an opinion that the 
difference is traceable to that cause. He found only argillaceous 
and calcareous matter. This discordance of opinion on the 
subject of claying and marling is not confined to this district, 
where the use of these mineral manures is of very limited extent ; 
it is equally prevalent in Norfolk, where it has been long esta- 
blished and extensively adopted. On clay-loams derived from 
the boulder clay, that clay, being composed of the wreck of the 
argillaceous beds of the oolitic and other formations mixed with 
fragmentary chalk, is spread at the rate of 70 or 80 loads to the 
acre nearly every 30 years ; and is considered to " freshen 
the ground," though the cultivators of such soils are shallow 
ploughers, and dread nothing so much as bringing up an inch of 
the boulder clay by a deeper furrow than usual. On the other 
hand, on the very lightest of the sandy loams of another part of 
Norfolk, I have seen a ferruginous sand spread as a dressing for 
the young clovers, and was informed that it had been found 
beneficial. 
The clays and marls of Norfolk consist, as I have stated else- 
where, either of chalk, obtained from the solid rock, or of frag- 
mentary and transported chalk, nearly pure in some cases, in 
others mixed with blue or yellow clay, the clay prevailing in 
some varieties, the chalk in others. When Young wrote his 
Survey of the Agriculture of that county he found so much dis- 
cordance of opinion among the best farmers, under equal condi- 
tions of soil and climate, respecting the quantity to be used, 
and the crop to which, as well as the season at which, it should 
be applied, as to render it impossible to deduce anything like a 
general principle from such conflicting elements. 
