12 



Chemical Composition and Commercial Value of 



stituents, and to render the insoluble phosphates completely 

 soluble. 



This precaution is not always observed by manufacturers, and 

 hence superphosphate made from coprolites is often of an inferior 

 quality. Properly dissolved, they are converted into a most 

 efficacious turnip-manure, for soluble phosphate of lime made 

 from coprolites is in every respect as good as soluble phosphate 

 made from bone or any other source. 



4. SUFFOLK COPROLITES (PSEUDO OR FALSE COPROLITES). 



These phosphoric deposits occur in the more recent tertiary 

 strata, as a layer varying from three to eighteen inches in thick- 

 ness, between the coralline crag and London clay. The Suffolk 

 crag is exceedingly rich in fossils, consisting partly of the frac- 

 tured and rolled bones of cetaceous and other animals, with some 

 fish-teeth, and chiefly of rolled water-worn pebbles, which were 

 formerly supposed to be the fossilized excrements of saurian and 

 other animals, for which reason they were called coprolites. 



Professor Buckland, however, snowed that they are not true 

 fossil excrements, but in all probability calcareous pebbles which 

 have undergone a peculiar metamorphosis, and become impreg- 

 nated with phosphoric acid by long-continued contact with 

 decaying animal and vegetable substances. 



The name pseudo or false coprolites, which Professor Buck- 

 land proposed for them, has been generally accepted by the 

 scientific world. In commercial phraseology, we have to under- 

 stand by Suffolk-coprolites, or crag-coprolites, or pseudo-coprolites, 

 the mixed fossil bones, fish-teeth, and phosphatic pebbles which 

 occur in the Suffolk crag. 



These phosphatic matters are distinguished from the grey- 

 coloured chalk-coprolites by a brownish, ferruginous colour, and 

 a smoother appearance. They are very hard, and yield on 

 grinding a yellowish-red powder. 



Analysed in the manner usually adopted in commercial analyses, 

 the composition of several samples of ground Suffolk coprolites 

 may be illustrated by the following tabulated results : 



General Composition of Suffolk Coprolites. 



