4\) 



rial, which we are taught to regard as by itself so generally prejudi- 

 cial to fertility. This ought to exhibit an encouraging picture to 

 those districts not directly within the limits of the marl tract, where 

 some of the strata possess the green substance in sensible pro- 

 portion. Tt expands most materially the limits of the territory 

 where marling may be introduced, and points to many beds as fer- 

 tilizing, which otherwise would be deemed wholly inefficacious." 



If such then be the effects of this material, even under circum- 

 stances where comparatively little advantage could have been antici- 

 pated, and if such moreover be the concurrent experience of those 

 by whom it is daily and extensively employed, we are fully author- 

 ised in the belief, that in the Eocene beds of our own state, though 

 in general less rich in the fertilizing ingredient than the secondary 

 strata of New Jersey, the agriculture of eastern Virginia possesses 

 a new and most valuable resource. 



The chemical examination of these marls, with a view to precise 

 results, being a matter requiring much time and labour, has as yet 

 been carried on only to a small extent. But, a thorough analysis 

 of all the important varieties and an exact determination of the pro- 

 portion of the various constituents, especially the greensand, or the cal- 

 careous matter in different localities, will be a work from which much 

 practical good may be derived. By the light of such results alone, can 

 the farmer be safely directed in applying it to the soil, or be pro- 

 perly guided in distinguishing between a material which is spurious, 

 and one which will be found salutary in its effects upon the land. 



The following results are to be looked upon as approximate de- 

 terminations, but will serve to illustrate the composition of several 

 varieties of the marl : 



COMPOSITION OF GREENSAND (EOCENE) MARLS. 



Doctor Corbin Braxton's, Silica and alumina, &c. 50 



Carbonate of lime, 10 



Greensand, 38 



Gypsum, 2 



Walker Tomlin's, lower stratum, Silica and alumina, 60 



Carb. lime and gypsum, a trace. 

 Greensand, 40 



Conrad Webb's, Silica and alumina, &c. 30 



Carbonate of lime, 45 



Greensand, 25 

 7 



