PKxuosE.j PHOSPHATES OF ENGLAND. 87 
quartz, obsidian, and grit. The calcareous matter is composed mostly of 
sponge-spicules, spines and plates of echiuoderms, minute shells, polyzoa, 
bivalve entomostraca, microscopic corals, forarniu iters, and calcareous 
concretions. 1 There are also in the bed u lumps of Chalk marl 2 which 
have fewer green grains in them than the matrix in which they are em- 
bedded." From this and other facts Mr. Fisher concludes that these 
phosphate beds seem to have been washed out of a calcareous marl, 
similar in character to the marl which lies above it. In short, he con- 
tinues, the nodule bed is a condensation of the " Chalk marl with glau- 
conite grains." On the other hand, Mr. Sollas thinks that the nodule 
bed has been derived from the destruction of the underlying Gault. The 
Gault contains nodules and fossils, but not nearly so many as the over- 
lying bed. Mr. Fisher urges against this hypothesis that the nodules 
of the Gault are smaller and of a lighter color than those of the nodule 
bed proper. Though the nodules are of a lighter color on the surface, 
the interior is of a color very similar to that of the Greensand nodules. 
Mr. Sollas shows that by the action of hydrochloric acid the Greensand 
nodules assume this same color on the surface, and consequently it is 
possible that the Gault nodules may have been acted on by water, acidu- 
lated by some acid or acid salt, percolating through the bed, and thus 
had their surfaces bleached. 
The phosphatic part of the nodule bed consists of shell casts, fossils, 
and nodules. There are numerous species of Rhabdospongia, Bonneyia, 
Acanthophora, Polycantha, Retis, and Uylospongia, besides many other 
Cretaceous forms, The nodules and casts are of a black or dark-brown 
color and have a very variable specific gravity and hardness. 
Many of them are worn, broken, and rounded, showing them to be 
clearly derivative masses, while others are perfect in shape and show 
no signs of having been removed from their o'riginal bed. 3 The deriv- 
ative fossils and nodules are covered with Plicatulce, and the smooth, 
broken surfaces of many of them, which are coated in this way, show, 
as Mr. Fisher thinks, that they must have been phosphatized before 
being deposited in their present bed, and he thinks that the phos- 
phate was concentrated from a carbonic acid solution by animal mat- 
ter. Besides the shell casts and fossils, there are two distinct vari- 
eties of nodules proper. The first is a reddish-brown and utterly 
shapeless variety. It is very soft when freshly dug, never becoming 
harder than ordinary chalk. 4 It has a very light specific gravity and 
is invariably rich in phosphoric acid. 5 A second variety is much more 
plentiful than the last. It consists of a dark-brown mass of a very 
variable shape. It is hard and heavy. It varies from pieces of micro- 
1 W. J. Sollas : Quart. Jour. Geol. Soc. London, vol. 2d, 1872, p. 398. 
2 0. Fisher: ibid., vol. 29, 1873, p. 53. 
3 0. Fisher: ibid. 
4 Paine and Way : Jour. Royal Agric. Soc., 1848. 
5 See analyses. 
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