are either amorphous or finger-shaped; the coprolites from
the Greensand are of a black or dark-brown colour; while those from the
Gault are greenish-white on the surface, brownish-black internally.
Samples of Cambridgeshire and Suffolk coprolite have been found by A.
Voelcker to give on analysis phosphoric acid equivalent to about 55 and
52.5% of tribasic calcium phosphate respectively (_Journ. R. Agric. Soc.
Eng._, 1860, xxi. 358). The following analysis of a saurio-coprolite
from Lyme Regis is given by T. J. Herapath (ibid. xii. 91):--

Water 3.976
Organic matter 2.001
Calcium sulphate 2.026
Calcium carbonate 28.121
Calcium fluoride not determined
Calcium and magnesium phosphate 53.996
Magnesium carbonate 0.423
Aluminic phosphate 1.276
Ferric phosphate 6.182
Silica 0.773
------
98.734

An ichthyo-coprolite from Tenby was found to contain 15.4% of phosphoric
anhydride. The pseudo-coprolites of the Suffolk Crag have been estimated
by Herapath to be as rich in phosphates as the true ichthyo-coprolites
and saurio-coprolites of other formations, the proportion of P2O5
contained varying between 12.5 and 37.25%, the average proportion,
however, being 32 or 33%.

Coprolite is reduced to powder by powerful mills of peculiar
construction, furnished with granite and buhrstones, before being
treated with concentrated sulphuric acid. The acid renders it available
as a manure by converting the calcium phosphate, Ca3P2O8, that
it contains into the soluble monocalcium salt, CaH4P2O8, or
"superphosphate." The phosphate thus produced forms an efficacious
turnip manure, and is quite equal in value to that produced from any
other source. The Chloritic Marl in the Wealden district furnishes much
phosphatic material, which has been extensively worked at Froyle. In the
vicinity of Farnham it contains a bed of "coprolites" of considerable
extent and 2 to 15 ft. in thickness. Specimens of these from the Dippen
Hall pits, analysed by Messrs J. M. Paine and J. T. Way, showed the
presence of phosphates equivalent to 55.96 of bone-earth (_Journ. R.
Agric. Soc. Eng._ ix. 56). Phosphatic nodules occur also in the
Chloritic Marl of the Isle of