45 



OP THE SEVERAL BEDS COMPOSING THE EOCENE FORMATION. 



In treating of the accompanying Miocene in the beginning of this 

 section of the report, our descriptions have been confined chiefly to 

 those beds which occur remote from the rivers upon the highlands, 

 and no mention has been made either of the white friable sand or 

 olive-coloured clay already frequently noticed in describing the over- 

 lying strata on the Pamunkey. 



The first of these, though once the repository of shells and other 

 fossils, is now entirely destitute of carbonate of lime. A small quan- 

 tity of gypsum in a minutely divided state seems to be its only in- 

 gredient of any value, and the amount of this present in the speci- 

 mens I have examined is much too inconsiderable to give the mate- 

 rial any agricultural importance. 



The olive earth, which is frequently an extensive layer, has also 

 lost all the calcareous matter which it once contained; but a further 

 examination, chemical and geological, of this material, will be required 

 before its nature can be exactly determined, or the possible applica- 

 tions of which it may admit can be ascertained. 



The upper bed of the Eocene, characterised in most of the locali- 

 ties by the gypsum which it contains, is worthy of especial conside- 

 ration on account of this valuable ingredient. In specimens from 

 the James river, from five to eight per cent, of this substance has 

 been found in a divided state, at the same time that a considerable 

 additional quantity in a massive form exists in various parts of the 

 same stratum. 



On the Pamunkey this stratum is not so thick, and is perhaps less 

 abundant in the sulphate of lime. The lower beds, in some cases 

 containing a marked proportion of shelly matter, and in others hav- 

 ing almost none, are more especially distinguished by the larger pro- 

 portion of another and even more important ingredient, to wit, the 

 greensand. Both on the James river and the Pamunkey, their rich- 

 ness in this material gives them an agricultural value which perhaps 

 no proportion of calcareous matter by itself, however great, would 

 be able to impart. The illustrations of its beneficial effects, and the 

 general observations upon its employment as a manure or marl, 

 which will hereafter be presented, will, I think, manifest the justice 

 of this opinion, and give a sound confidence to those who are dis- 

 posed to make trial of its powers. 



