30 
oxide of iron, about 12 ft. At a coprolite working on tbe left side 
of tbe line, looking towards Cambridge, a few yards from tbe edge 
of tbe cutting, tbe bed increases in thickness to two feet. At a 
large working on tbe bill tbe conglomerate bed is about six feet 
thick, the section being as follows:—1, sandstone, on which con¬ 
glomerate rests; 2, conglomerate (6ft.); 3, flaggy sandstone, not 
exceeding 1 ft. in thickness (often less), and surface soil. Tbe 
lower part of tbe conglomerate here is darker in colour and more 
indurated than tbe upper. On tbe other side of tbe road there is 
another working where the nodules lie in a loose sand, and tbe 
phosphate bed is about one foot thick. There are several other 
workings in the neighbourhood. The conglomerate contains phos- 
phatic nodules and pebbles in about equal proportions. The bed 
is dug out, sifted, washed, and laid in heaps, then conveyed into 
sheds, where the nodules are picked over by hand. The quantity 
of phosphoric acid in the nodules varies from 15 to 22 per cent. 
The deposit consists of ferruginous sand, more or less indurated, 
rolled pebbles, light brown nodules of phosphatic matter (which 
have an earthy fracture and often contain remains of shells), and 
lumps of hardened clay. The nodules contain a much larger per 
centage of alumina than those of the Cambridge Greensand. This 
would indicate that the phosphatic nodules had been formed of clay 
soaked in decomposing animal and vegetable matter, since the 
alumina could not be derived from animal or vegetable sources. 
The nodules are often covered with perforations, which Mr. A. 
Wanklyn discovered to be the work of small bivalves, of which he 
obtained several species. The remains of organic life found in this 
deposit exist in different states of mineralization, and some are 
coeval with the bed, whilst others have been washed out of pre¬ 
existing deposits. Of vegetable remains there are large masses of 
silicified wood, apparently from the Purbeck; smaller fragments of 
phosphatized wood, often bored by a new species of Pholas (P. 
Dallasii Walk.) ; and a cycadaceous cone evidently from the 
Wealden. * The animal remains include numerous rolled and 
water-worn bones and teeth of Peptiles and Fishes, and traces of 
Mollusca in two distinct conditions. Some of the latter consist of 
phosphatic casts, which are so much worn that it is impossible to 
identify them ; they are probably derived from the Kimmeridge 
and Oxford Clays. Ammonites Uplex occurs abundantly, and one 
or two other species are found. Phragmocones of JBelemnites like- 
* Described by Mr. Camithers as Cycadeostrobus WalJceri. 
