CALCAREOUS MANUKES-APPE^-DIX. J97 



Marl in this wide sense may tiien be first divided into tlie two following 

 great classes : 



I. Fine argillo-calcareous earth, described above as " true marl," and which 

 is not of itself shelly, even when in alternate layers with shells, and contains 

 no separate silicious sand, or other coarse of heavy matters which could 

 not remain, in a finely divided state, suspended in water flowing in 

 but a moderate current. Tliis marl, as stated above, is abundant and rich 

 in some parts of Europe ; but so rare and inconsiderable in quantity in 

 eastern Virginia, as to be scarcely worth naming for agricultural use. 



n. The second great division is shell-marl, which may be again divided 

 into the two kinds, of 1, recent fresh-water shells, and 2, fossil or ancient 

 sea-shells, left on and covered within what is now high land, up-heaved from 

 the former bottom of tlie ocean, by ancient convulsions, or other great 

 changes of the level of the earth's surface. 



1. The first of these kinds is common in some parts of Scotland, and is 

 found also in Vermont and probably other parts of the northern states, 

 but is not known to exist in Virginia. It is formed by the gradual accu- 

 mulation of the shells of periwinkles or other small fresh-water shell-fish, 

 at the bottoms of the small and shallow lakes in which the animals had lived. 

 When the bottom had been raised by this accumulation, and by deposites 

 from this and other sources, nearly to the level of the surface of the lake, wa- 

 ter plants began to grow, and to form a new accumulation of vegetable and 

 earthy deposites ; and finally the lake was thus changed to a peat-bog, wet 

 and miry, but free from standing water. It is under the peat, and some- 

 times at considerable depths, that this peculiar and very rich marl is found. 

 It is said to be almost pure calcareous matter, and has been sold by the 

 bushel, in great quantity for manure in Scotland. — {Edinburgh Farmers' 

 Magazine.*) 



2. The second is for us the only important division of shell marl, em- 

 bracing all the immense body of fossil sea-shells which underlies nearly all 

 of the tide-water or tertiary region of Virginia. This is also of two kinds 

 designated by Professor Lyell, according to their geological age and forma- 

 tion, as miocene and eocene ; and these have each the several agricultural 

 varieties and sub-varieties named in the table above, and which will be 

 hereafter described in order. 



As the terms " miocene" and "eocene" are now of universal acceptation 

 among scientific writers, and are generally understood by agricultural 

 readers on marl, and therefore are convenient for designating the vefy 

 diflferent descriptions of marls to which they have been applied, they will 

 be here used. If the difference between these two kinds were merely 

 geological, or in regard to comparative ages of formation, or to the respec- 

 tive fossils of each, it would be useless to preserve it in writing on agricul- 

 ture, however marked the difference, and however interesting, to the 

 geologist. But there is also a difference of agricultural character and value 

 in these two kinds of marl. In relation merely to each other, the terms 

 eocene and miocene may be sufficiently understood as the older and newer 

 formations. But it will not do as well to substitute the latter terms, because 

 they are not correct generally, or in relation to other marls and geological 

 formations. For there are some much older than the eocene, and others 



• In the Edinburgh Farmers' Magazine, vol. iv. p. 153, there is an interesting article 

 (most of which was republished in the Farmers' Register, vol. i. p. 90,) describing a large 

 body of this kind of shell marl, under Resteneth peat-moss, Forfar, Scotland. Most of 

 the shells are of the water snail {helix putris, Linnseos,) others are bivalves, (generally 

 tellina, animal telhys, Lin.) From this deposite, the i>roprietor had sold as much for 

 manure as brought him £12,000 sterling, in the 12 years after its ase had been begun. 



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