196 



CALCAREOUS MANURES-APPENDIX. 



broken veiy small, witli some only of the veiy smallest entire. The pure 

 argillaceous marl is blue (though sometimes of bufFcolor,) firm and compact 

 breaks easily, but does not bend however moist, and is cut smooth by a 

 knife, leaving a surface like that of hard soap. This marl contained, in 

 the argillaceous part, free from the shelly parts, only 10 per cent, of calca- 

 reous matter. Several other specimens, from other localities in the same 

 region, were about the same strength. Therefore, even if more plenty, 

 there would seem to be no inducement to use our true marl, where the 

 beds of fossil shells, called marl, and usually so much richer in calcareous 

 matter, can be drawn from. But in Europe, clay marl is reported as lich 

 as 40 to GO per cent, of calcareous matter, and indeed richer, gradually 

 running into lime-stone. In our lime-stone mountain region, (and especially 

 in the places of ancient lakes and ponds, now drained or filled up, there 

 probably may be found bodies of true or clay marl, comparing in strength 

 as manure, and in abundance, with the valuable European deposites. 



But though it is proper to know, and to bear in mind, what is understood 

 by the term marl by mineralogists, and by the well informed English and 

 French agricultural writers, in regard to the extensive marlings in those 

 countries, yet it is necessary in Virginia to conform generally to the usage 

 which gives the name of marl to all earths mixed with fossil shells ; and as 

 the term is so far improperly extended, I would carry it still farther, and 

 make it embrace all natural calcareous earths not of stony hardness. This 

 arrangement then would indeed include true marl, but merely as one class, 

 and that one of the least noticeable for abundance or value of all in this 

 country. The following scheme of classification will conform to this view, 

 and serve to make more clear the descriptions that will follow. 



f 1 ARGILLO- 

 CALCAREOUS 

 MARL. 



(K^positcd in 

 and i'lom 

 still walor. 



r 



MARL, or 

 Shelly earth, 

 or earth 

 otherwise 

 calcareous in 

 part. 



(a 



U. SHELL 

 MARL. 



1. FRESH 



WATER 

 SHELLS, 

 grown ill &, 

 dcj)0.silt;d 

 a! bottom of 

 lakes. 



2. FOSSIL 

 SHELLS, 

 or Ancient< 

 Sea Shells 



f MIO- 

 CENK 

 MARL. 



YeKow Mio 

 cenc Mail. 



aa. \ i'Uvw 

 sandy iii.iii. 



bb. Yellow 

 cluy )n.irl. 



I b. Blue 

 (^ Marl 



CC. Blue 

 marl. 



aiHiy 



(Jd. Blue clay 

 marl. 



(c 



EO- 

 CENE 

 I^MARL 



Calcareous 

 Marl, with 

 very little ii 

 any Green - 

 sand. 



d. Calcareous 

 matter and 

 iCre-^nsand, 

 l)c)th consi- 

 derable. 



c. Gypseous or 

 Green -sand 

 earth, with 

 very little if 

 any shelly or 

 calcareous 

 matter. 



