202 CALCAREOUS MANURES- APPENDIX. 



the current so long, or carried so far, before being deposited. 1 he few rich 

 clay marls of Prince George are of the first named variety, or composed 

 entirely of fine fragments of shells intermixed with clay. The much richer 

 marls in and about Williamsburg are of the other kind, there being also 

 numerous whole shells in place, as well as the interstices being filled almost 

 entirely by water-borne fragments, and fine powder of other shells. The 

 other contents, making from 15 to 25 per cent, of the body, are principally 

 of a very fine clay of pale yellow, and much less of silicious or white quartz 

 sand, oxide of iron, and green-sand. Much of the same kind of rich marl 

 is also in other parts of James City and York, in the lower part of Sur- 

 ry, and in Isle of Wight, New Kent, and King William counties, which I 

 have seen— and probably throughout the middle belt of the marl region 

 of Virginia. There has been little or none of these rich clay marls seen 

 by me in the upper range of marl counties, (those next the falls of the 

 rivers,) and not much more near to the eastern limits, or next to where 

 the marl dips so deeply, as to disappear from the surface and is accessible 

 only by deep digging. Perhaps observations more extended, and more ac- 

 curate than mine have been, might present different conclusions. 



The marls just described, when separated mechanically, (by the sieve 

 and by carefully washing in water,) seem to consist, for the much greater 

 part, of pure shelly matter, mostly in large or small fragments, slightly co- 

 lored by brown oxide of iron, and the remainder of a very fine and ap- 

 parently pure pale yellow clay. But this clay is also composed in part of 

 finely divided carbonate of lime ; and the fine shelly matter is intermixed 

 with some silicious sand and a little green-sand. The bed of marl near 

 Surry Court House, (which is similar to the marl at most other places 

 thereabout,) is of this kind and general character ; and from it, a large 

 body of land has been manured with great benefit. This body of marl was 

 reputed to be among the richest in green-sand. From a much larger 

 sample of the marl of this bed, carefully selected by the proprietor, at my 

 request and for my examination, an average portion taken was compos- 

 ed as follows : 



1780 grains, separated mechanically, by the sieve and by washing in 

 water, consisted of 



Carbonate Fine argillaceous Silicious Green sand, 

 of lime. earth. sand. 



1036 grains of shells and coarse frag- 

 ments, nearly pure, and so counted, 1036 

 433 grains fine shelly fragments, &c., 



which consisted of - - - 268 - - - 120 45 



277 grains fine yellow clay, &c., 



which consisted of - - - 65 - 212 



34 loss in the process. 



1780 1369 212 120 45 



Which may be stated of parts to the hundred thus : 



100 grains of marl contained of carbonate of lime, 77 grains. 

 Silicious or quartz sand, very pure and white, 6| " 



Green-sand ....... - 2J " 



Fine yellow clay or argillaceous earth, (and the loss in the latter pro- 

 cess,) ........ 13s <« 



100 " 



The richest bodies of these marls show very few shells, or even frag- 

 ments, and have a homogeneous texture and appearance to the eye, like 

 a very impure chalk or sandy clay. Such marls are in James City, New 

 Kent, King William and Middlesex counties. The following are some of 

 them of which I have analyzed specimens : 



