450 EOCENE MARL. 



yet laid before the public, in the " Essay on Calcareous Manures" 

 or elsewhere, have been in relation to the miooene marls. 



My personal examinations of marl, in place, have not been ex- 

 tended to the Rappahannock. From such information as has 

 reached me, I infer that the marls of that basin are generally inuch 

 poorer in calcareous matter than those of the basins of James 

 river, York, Mobjack bay, and Piankatuck river. 



Eocene Marl. 



(c) Calcareous marly containing but little green-sand. The ex- 

 istence in Virginia of the marl now known as eocene, was first dis- 

 covered in 1819 by myself, in the south bank of James river, un- 

 derlying the promontory of Coggins Point ; and in the same year 

 it was tried as manure. The texture and general appearance of 

 this marl were obviously peculiar ; and its effects as manure were 

 soon also observed to be in some measure different from and supe- 

 rior to those of the other marls, which I had then used, and which 

 were all of the kind now distinguished as miocene. At that time 

 these terms had not been introduced, and for perhaps fifteen years 

 afterwards, I did not so much as hear of the terms " eocene" and 

 " miocene ;" but the difference of age, appearance, and agricultural 

 character of the two kinds were not therefore the less evident and 

 obvious to my uninstructed observation. The manifest difference 

 of effect, as manure, was then ascribed by me to the general if not 

 universal presence of a small proportion of sulphate of lime, or 

 gypsum, in the eocene marl. The belief in the general presence 

 of gypsum was very early induced by my seeing in a few places 

 small crystals overlying and in contact with the surface of the bed 

 of marl ; and also by the apparent results o$ such poor attempts 

 as I subsequently made to ascertain the presence of this substance, 

 by means of chemical tests. Upon such imperfect trials, and the 

 still more imperfect knowledge and skill which I could apply to the 

 investigation, very little reliance ought to have been placed. Never- 

 theless. I thence inferred that there was universally present and 

 diffused through the body of this marl a small proportion of sul- 

 phate of lime, and subsequent agricultural practice has supplied 

 the confirmation, which has not yet been sought for by the supe- 

 rior chemical knowledge and skill of any other and later investi- 

 gator. In the earliest publication of my views on calcareous ma- 

 nures in 1821, the gypseous character of this particular body of 

 marl was affirmed, and the peculiar character of the results of the 

 first experiments with it stated.* And in the edition of 1832 of 

 the "Essay on Calcareous Manures," the general and full descrip- 



* American Farmer, vol. iii., p. 317, and also the same experiments num- 

 bered 18, 19, 20, of the present edition of "Essay on Calcareous Manures." 



