Geoloyij of Norfolh. 
181 
than to use that raised on the spot. An analysis of the chalk of 
different localities, and at different depths, is therefore highly 
desirable. That given by Dr. Playfair in a recent number of 
this Journal, of a specimen which I sent from P'rettenham Com- 
mon may be considered as representing the composition of the soft 
upper chalk of Norfolk. It contains, it will be remembered, a 
portion of phosphate of lime, though not in a sufficient quantity 
to produce the effects attributed to it in retarding for a time the 
action of bones, which must be due to some other cause. 
Practice has not yet settled the relative merits of marl — that is 
to say, of pure chalk — and of clay — that is to say, of a natural 
mixture of fragmentary chalk with sand and clay. On this point as 
much contrariety of opinion prevails, at the present time, as when 
Young made his Report to the Board of Agriculture. Much of 
the marl of East Norfolk consists of a slight mixture of sand and 
clay in a mass composed principally of chalk; and the clay of 
East Flegg consists of a base of clay rendered more or less cal- 
careous by a mixture of fragmentary chalk, the proportion of 
which increases westward and northward, until in the north-west 
of the county it differs but little from much of the transported 
chalk called marl in East Norfolk. There are few portions of 
the chalk range of England which have not been acted upon in 
some degree or other by the operations which produced the drift, 
and where deposits similar to some of those of Norfolk may not 
be expected. Where these natural mixtures of chalk and clay 
are wanting, large portions of the range are contiguous either 
to the tertiary clays of the London and Hampshire basins, or to 
the clays of the Gault, Kimmeridge, and Oxford beds. The ruins 
of the latter have contributed largely to the mass of the till of 
Norfolk ; and those of the London clay enter extensively into the 
composition of the till of Suffolk. In those cases where mixtures 
of these with chalk have not been effected by nature they may be 
produced artificially, chalk and clay being both accessible either 
as regards depth or distance. Experiments, therefore, in the 
application of the tertiary and oolitic clays alone, or mixed with 
chalk in different proportions, or with lime where chalk is too 
remote, are well worth the trial. In speaking of its accessibility, 
it must be borne in mind that a Norfolk farmer does not hesitate 
to remove " uncallow," that is sand and gravel, from three to five 
yards deep, to raise an equal depth of chalk, transported chalk, 
or till, as the case may be ; and in the pits at Thorpe-by-Norwich 
20 yards of " uncallow " are removed to obtain very little more 
than 20 yards of chalk. The work is performed in a manner the 
least advantageous, small portions only being cleared at a time, the 
"uncallow" removed to a considerable distance in wheelbarrows, 
the water at a certain level kept down by hand, and the fossil 
