COPROLITES 



949 



From the high per-centage of phosphate of lime recorded in these analyses, it must 

 be evident that coprolites are of great value to the agriculturist as fertilising agents. 

 Indeed, large quantities of so-called ' coprolites ' are thus employed. It should, however, 

 be distinctly understood that the term has been considerably extended in its meaning, 

 and is now applied to all phosphatic nodules used in the formation of artificial man- 

 ures, whatever may have been their origin. These nodules, or pseudo-coprolites, are 

 especially abundant in the Red Crag of Suffolk. This Crag is a marine deposit of 

 Pliocene (Upper Tertiary) age, rich in shells and other organic remains; and at 

 the base of the Crag there is a bed of rolled bones, teeth, and various animal exuviae, 

 derived from the London Clay, and associated with rolled pebbles rich in phosphate of 

 lime. These pebbles or nodules were first described by the late Prof. Henslow as true 

 coprolites, but it is certain, from their physical characters, that they have not a coprolitic 

 origin. Nevertheless, these pseudo-coprolites are equally rich in phosphate of lime, as 

 will be seen by the following analyses of two samples from the coast of Suffolk by 

 Mr. Herapath : * 



Phosphatic nodules, passing under the name of coprolites, are found at the junction 

 of the Lower Greensand and Gault, at the junction of the Gault and Upper Green- 

 sand, and at the base of the Chalk. 



In an excellent paper ' On the Phosphoric Strata of the Chalk Formations,' published 

 in the first number of Vol. IX. of the ' Journal of the Royal Agricultural Society of 

 England,' Mr. Way observes, that he has found the coprolites from Farnham in Surrey 

 to contain from 52 to 54 per cent, of bone-earth phosphate ; and that Dr. Gilbert had 

 informed him, that in several analyses which he had made of samples taken from 

 several tons of the ground coprolites, he had found the proportion of phosphate of 

 lime to vary between 55 and 57 percent. Mr. Nesbit ('Quart. Journ. of Chem. Soc.' 

 III. p. 235) found from 22-30 to 28'74 per cent, of phosphoric acid, which is equiva- 

 lent to from 48-31 to 59*07 of tribasic phosphate, in those from the tertiary deposits 

 of this county. 



Phosphatic nodules, or coprolites, are obtained from the base of the Gault at 

 Folkestone, and from the base of the Chalk at Cambridge. ' The Cambridgeshire 

 phosphatic nodules,' says the Rev. 0. Fisher, ' are extracted by washing from a stratum 

 (seldom exceeding a foot in thickness) lying at the base of the Lower Chalk, and rest- 

 ing immediately, without any passage-bed, upon the Gault. There is, however, a 

 gradual passage upwards from the nodule-bed into the Lower Chalk or clunch. The 

 average yield is about 300 tons per acre ; and the nodules are worth about 60s. a ton. 

 The diggers usually pay about 140. an acre for the privilege of digging, and return 

 the land at the end of two years properly levelled and re-soiled. They follow the 

 nodules to a depth of about 20 feet'; but it scarcely pays to extract them from that 

 depth. ' Quart. Journ. Geolog. Soc.' Feb. 1873. 



The following analyses of Cambridge coprolites are published by Dr. Voelcker iq 

 the Journ. of the Roy. Agric. Soc. for I860: 



1 Journal floy. Agric. Soc. Eng. 1851, 



