76 On the Phosphoric Strata of the Chalk Formation. 
Tliis marl is extremely ricli in fossil remains, amongst which a species 
of small scaphites are very numerous. 
The phosphoric fossils of the upper green-sand have also been 
found as far west as at Chard in Somersetshire. 
They were found to contain — 
Phosphoric acid . . 10 -16 percent. 
Equal to 20 • 97 bone-earth phosphate. 
The fossil phosphates from the gault require little further 
notice, as they have hitherto been found only thinly scattered 
through the mass of clay. Dr. Fitton, in the Memoir quoted 
above, mentions that at Ridge in Wiltshire, and at Mildenhall in 
Suffolk, he found ammonites, &c. in conjunction with coprold 
concretions of phosphate of lime (pp. 247, 312). 
This stratum has been examined in different parts of the king- 
dom, in order to ascertain if a sufficient supply of fossils existed 
which might be profitably collected for agricultural uses. In all 
cases the analyses of the fossils showed them to be extremely rich 
in phosphoric acid ; but nowhere do they seem to exist in quan- 
tities large enough to pay the expenses of digging for them. The 
most common fossils are ammonites, oblong reniform masses, con- 
taining no specific organic remains (the coproid bodies of Dr. 
Fitton), and indurated wood. 
The following is an analysis of a large gault fossil from Farn- 
bam : — 
Insoluble silicious matter . 
•91 
Organic matter 
. 2-94 
Carbonic acid 
. 12-43 
Oxide of iron 
. 2-91 
Lime ..... 
. 47-46 
Magnesia .... 
•21 
Phosphoric acid 
. 24-28 
Water, fluorine, and loss 
. 8-86 
100-00 
The lower green-sand, taken as a whole, differs so widely in its 
agricultural value, that any general description of its character 
would be utterly useless. In the first instance, therefore, atten- 
tion will be exclusively confined to the fossiliferous bed of the 
upper part of this formation. This bed has been found to be 
so invariably persistent in its prominent features in localities 
widely separated from each other, that it is most important to bear 
in mind its exact geological position, viz. just heloio the gault, at 
its junction with the loicer green- sand. Another distinctive mark 
is, the usual accompaniment of a thin seam of iron-sandstone, to 
which a few scattered fossils often adhere. This band and the 
conglomerated fossils so completely obstruct the downward pas- 
