NOKTH-CAROLINA GEOLOGICAL SURVEY. 79 



In this country this part of the cretaceous system is wanting, 

 or has not yet been recognized. From its wide extent, both 

 in this country and Europe, it is, geologically speaking, an 

 important formation ; so also in an economical point of view 

 it is equally important, for it has been a source of revenue to 

 the agricultural community, not second even to guano. For 

 permanent improvements in the soil it is superior to this far 

 famed substance, its effects lasting from ten to fifteen years. 

 In New Jerse} r it first attracted attention from an accident : 

 some green sand being thrown out of a ditch upon a bank, 

 an exceeding fine growth of clover was the consequence. It 

 was immediately inferred that the substance upon the ditch 

 bank was the cause of this fine growth ; and hence a trial 

 was made of it. 



From many subsequent experiments and observations its 

 claim as a good fertilizer became established. This happened 

 more than fifty years ago, and ample experience in the mean 

 time has fully satisfied the agricultural community at large 

 that it is worthy the confidence which has been reposed in it, 



53. In the subsequent pages I propose to give a full 

 statement of the grounds upon which its reputation rests, 

 and also to furnish numerous analyses of the best and poorest 

 varieties of this substance. In the first place I deem it proper 

 to show its geological relations, and its relative position to 

 other beds of marl, inasmuch as it will aid in determinim'ng 

 in any given case whether the substance or beds in question 

 really belong to those which have received the common name 

 referred to. In all cases this is an economical question, or 

 may be thus used, inasmuch as the beds formed during this 

 geological era have a composition which fits them for the 

 purpose for which they have been so largely employed. Beds, 

 therefore, occupying their position may be supposed without 

 trial and without analysis to contain the active fertilizing 

 matter. It, however, cannot be determined by these external 

 observations, how much they contain, for it is found that they 

 are variable in composition, so far as quantity is concerned. 

 For the purpose of determining their commercial value, or 



