CALCAREOUS MANURES— APPENDIX. 213 



almost black when moist in the bank, though more of dark green when 

 dry. This deeper color is owing to the green giranules being present in 

 larger quantity; and generally, if not always, the lower part of the bed of 

 earth is richer in that ingredient than the upper. The empty impressions 

 which were formerly filled by shells are still found in penetrating below ; 

 but as the depth increases, first are seen some fragments, and then whole 

 shells, though greatly decayed, and the parts having scarcely any coherence. 

 Still, generally, even below, where these shells are most abundant, their 

 quantity would not furnish as much as two per cent, and generally not one 

 per cent., to the whole thickness of the bed ; and therefore the carbonate 

 of lime, though of course useful in proportion to its cjuantity, can give no 

 appreciable addition of value to the mass as manure. 



Here and there, but rarely, in the upper and dry part of this bed, crystals 

 of gypsum are fot;nd, generally so small as to be barely distinguishable 

 by the eye. In the lower and wet part, gypsum is never visible ; but it 

 is nevertheless believed to be always present in some proportion. 



But the important and most characteristic mark of the green earth is 

 present in the black granules called " green-sand," which give color to the 

 mass. To ascertain the presence of these granules, let a small sample of 

 the earth or marl supposed to contain them be dried, and then crumbled 

 between the fingers, or, if too hard for that, by being rubbed in a mortar, 

 not too finely and closely. Then take a pinch of the powder between the 

 thumb and finger, and sprinkle it very thinly over a piece of white paper. 

 If any of the separated grains appear black, (or green,) mash one of them 

 with the moistened point of a pen-knife ; and if it be " green-sand," the 

 granule v/ill mash like fine soapy clay, and make a vivid green smear. 



For greater accuracy, let the earth (or marl) be well washed by agitatioh 

 in water, and pour oa the pure clay and other lighter matters which will 

 remain longer suspended in the fluid. The grains of green-sand will then 

 be left with nothing else but the quartz or silicious sand, and moreover the 

 former will be made more perceptible, in consequence of being cleared by 

 the washing of any previous covering of fine clay. 



My first published account of this earth was made in or about the 

 year 1828, in the old series of the 'American Farmer.' A much 

 more extended article "On the Gypseous Earth of James River," I 

 afterwards published, July, 1833, in the first volume of the Farmers' Re- 

 gister, beginning at page 207. Though up to that time I had never so 

 much as heard of the term "green-sand," and though I adopted and used 

 the nevi^ and unauthorized designation of "gypseous earth," the earth in 

 question was described so minutely and accurately that it was impossible 

 for any intelligent and attentive reader of tlie article, and subsequent ob- 

 server of the kind of earth in question, to mistake the subject of descrip- 

 tion. I trust that I may be pardoned for thus specifying my claim to the 

 first discovery of this earth in Virginia, inasmuch as that merit (if it be 

 one) would he ascribed by every otherv/ise unirjformed reader of the first 

 report of the geological survey of Virginia, and some other of the publica- 

 tions from the same source, to the author of these pieces. Upon this 

 occasion, it would be improper to say more on this question than thus con- 

 cisely and explicitly to assert my just rights. 



Before proceeding to offer the more precise and more valuable informa- 

 tion concerning this earth obtained by very recent investigations, it will be 

 proper to state something of the progress and changes of opinion on this 

 subject, which operated at different times either to encourage or to obstruct 

 the use of this earth as manure. 



From 1818 to 1835 inclusive, I made numerous trials, and in some cases 



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