. GREEN-SAND SUPPOSED IN MIOCENE MAULS. 487 



and thus to place in connexion with these results, that all the dark 

 green or blackish earth (Z>) of Coggins Point gave out these suf- 

 focating fumes, and also the gray clay (E) below, and most power- 

 fully and that no such product was found from any of the very 

 shelly bands. Thus it would seem that most generally the non- 

 calcareous earths (or nearly non-calcareous) gave out fumes, and 

 the calcareous not. But exceptions were found to both. And of 

 the New Jersey green-sands, containing no carbonate of lime, six 

 specimens were tried at red heat, of the beds most esteemed for 

 manure, and not the slightest disengagement of such fumes was 

 produced.* 



This extrication of sulphureous fumes by the first beginning of red 

 heat, is a sure indication of the presence of sulphuret (or bi-sul- 

 phuret) of iron. And wherever this exists in contact with marl, and 

 with the access of air and water, first the sulphate of iron will be 

 formed, and next this salt will decompose as much carbonate of lime 

 as its quantity will act upon, and so form gypsum. Therefore, 

 wherever the sulphuret of iron is present in marl, or is put in con- 

 tact with it, in soil, it is certain that, in the same proportion, carbo- 

 nate of lime will be decomposed, and sulphate of lime formed. Of 

 course no addition of other gypsum is needed, or could act if 

 Applied, on land recently supplied, in marl, with enough sulphuret 

 of iron, even if the partial previous decomposition of the latter 

 had not already formed gypsum in the bed of marl, as is usually 

 the case. 



Of Green-sand as an ingredient of Miocene Marls. 



In a previous page (439), the presence of green-sand in mioccne 

 marls, as an important and general ingredient, was denied ; and the 

 subject then passed by, with the promise of its being subsequently 

 resumed. Having treated of the gypseous earth and of eocene 

 green-sand marls, of both of which green-sand forms large and im- 

 portant proportions, it is now most appropriate to inquire into the 

 alleged extent and operation of this substance in miocene marls. 



In 1834, Professor William B. Rogers (then and long before a 

 resident of lower Virginia) announced that he had discovered green- 

 sand to be a considerable ingredient of nearly all the many ordinary 

 miocene marls which he had examined either in place or by speci- 

 mens ; and from which observations he inferred the same adrnix- 



* The New Jersey "marls" thus tried were selected by the writer from 

 the pits of Josiah Heritage and Thomas Bee of Gloucester, and Henry 

 Allen, Allen Wallace, J. Riley, and J. Cauley, Salem county. The same 

 results were found as to the poorer (or less valued) overlying strata of 

 Heritage, R. Dickenson, J. Cauley, and also of the barren green clay or sub- 

 soil. See all described in my report, on the New Jersey green-sand earths, 

 Fanners' Register, vol. x. p. 429 



