47 



rests upon strata of this description, we are led to regard it as fur- 

 nishing an immense addition to the resources of the state, and as 

 holding out to our enterprising farmers situated within its limits, a 

 new motive to persevering and active research. Let it not be sup- 

 posed, however, that wherever the Eocene occurs within our state, 

 it will be found to present the same materials in the composition of 

 its strata, as have been found in the localities already examined. 

 Much diversity in this respect may, and probably does exist. On 

 the Mattapony, as already stated, the greensand is frequently re- 

 placed by beds of clay of a dark lead colour ; while on the Potomac, 

 Rappahannock, Pamunkey and James, variable but generally large 

 proportions of the greensand occur, and the probability is, that fu- 

 ture inquiries will develope similar diversities in the materials of the 

 beds in other yet unexplored portions of the district. Constancy in 

 the character of the embedded fossils is all that is necessary to a 

 geological identity of the formations, and this constancy may exist 

 at the same time that there is a considerable diversity in the mate- 

 rials in which they are enclosed. It is almost certain, however, that 

 throughout a large portion of the region in question, extensive and 

 valuable beds containing the greensand do exist, and that even in 

 the highlands they might be reached by excavations descending not 

 very far beneath the lower limit of the Miocene or ordinary marl. 



ON THE VALUE OF THE EOCENE GREENSAND MARL IN AGRICULTURE. 



From the descriptions already given of the materials of the vari- 

 ous beds of Eocene, it will be seen that many of them contain ingre- 

 dients which have long been recognised as valuable when applied to 

 land. The gypsum in some, and the carbonate of lime in others, 

 will at once bespeak the favour and confidence of the agriculturist, 

 and no observations, either as to their usefulness or mode of applica- 

 tion, will be necessary to give them the importance they deserve. 

 But the characteristic and principal ingredient of a large number of 

 these beds, the greensand, possesses claims to our attention which 

 are equally indisputable, though not so generally appreciated or un- 

 derstood. Experiments within our own state on this material, as 

 furnished by the Eocene deposites, though few, and on a very limited 

 scale, have been so far satisfactory. But as the marls containing 

 this substance, which have been employed, have also in most cases 

 contained a notable quantity of gypsum, or of calcareous matter, all 



