194 CALCAREOUS MANURES— APPENDIX. 



NOTE IV. 



DESCRIPTION AND ACCOUNT OF THE DIFFERENT KINDS OF MARL, AND OP THE GYP- 

 SEOUS EARTH, or THE TIDE-WATER REGION OF VIRGINIA. 



Report to the State Board of Agriculture, by Edmund Ruffin, Me)nber and 

 Corresponding Secretary of the Board. 1842. 



Within the last twenty-five years there have been produced from the ap- 

 plication of calcareous manures more improvement and benefit, both agri- 

 cultural and general, in lower Virginia, than from all other means and 

 sources, numerous and valuable as have been the agricultural improve- 

 ments made. And for the latter half of that time, no one agricultural sub- 

 ject has been treated of more at length in the publications of this state. 

 Still, there is much required to be known ; and it has very often, and not 

 less so recently than formerly, been required of the writer, who has furnish- 

 ed to the press the larger part of all that has thence proceeded on this sub- 

 ject, to give answers to inquiries, which, however variously v/orded, amount- 

 ed in substance to the question, " What is marl !"— or " Is my marl, (or what- 

 ever earth was so termed,) g-ooc/ marl, and likely to be profitable as manure ?" 

 It has therefore appeared to the writer that it would be useful to prepare 

 something like a natural history or general and full description of the marls 

 of lower Virginia ; and also of the kindred and yet very different mineral 

 manure, the gypseous earth, or " green-sand" earth, concerning which latter 

 so much error and delusion have been spread and long maintained, and 

 so little of truth or useful information derived from the sources generally re- 

 spected as the highest authority. 



The main difficulty in the treating of this subject is presented in the out- 

 set in the very term " maW," which is altogether misapplied now in this 

 country, though not so much as it has been and perhaps still is in England. 

 Since this general course of misapplication was set forth by the writer at 

 length in the ' Essay on Calcareous Manures,' there have become general 

 in this country still other misapplications of this always misapplied term. 

 For the " green-sand" earth of iSew Jersey, which before had been called 

 " marl" by illiterate farmers only, has been since received under that name 

 by chemists and the scientific reporters of geological surveys ; and thus 

 confusion has become still " worse confounded." In the following pages, I 

 shall be compelled, as heretofore, to yield in part to such misapplication of 

 the term ; but at the expense of some otherwise useless repetition, and fre- 

 quent explanation, shall hope to avoid misleading readers as to each of the 

 particular earths under consideration. And, in general, I shall in no case 

 apply the term marl to any but a calcareous earth, and of which the calca- 

 reous ingredient or proportion of carbonate of lime is deemed sufficient to 

 constitute the most important, if not indeed forming the only important or 

 appreciable agent of fertilization ; and therefore I shall not so designate 

 either the fine clays, (not calcareous, or very slightly so,) called marl in 

 England, or the green-sand earths of New Jersey, Delaware or Virginia, 

 when containing very little or no carbonate of lime. 



TVue marl, as correctly understood and described by mineralogists, is 

 a fine calcareous clay, containing very little silicious sand, and none coarse, 

 or separate; of firm texture— not plastic, or adhesive; does not bend 

 under pressure, but breaks easily. It is manifest, fi-om its laminated ap- 

 pearance and fracture that this true marl has been originally suspended in ra- 

 pidly flowing waters, and deposited at the bottom by subsidence, when the 

 waters became comparatively still ; as when a rapid river, turbid with calca- 

 reous clay, reached a lake. Thus, from its manner of formation, such marl, 

 however argillaceous, was of a texture very different from the almost pure, 



