464 GYPSEOUS EARTH AT EVERGREEN. 



make the whole stratum a calcareous marl ; of perhaps 80 per 

 cent, or more of carbonate of lime the earth filling the shells 

 and between them being the same black earth, as rich as before 

 in green-sand. At top, some very large and perfect shells of 

 ostrea compressirostra, and another much thicker ostrea, not 

 known.* The shells mostly very large turritdlce of different 

 species near bottom fewer of these, and mostly crassatellce. 

 The shells nearly as numerous as before, at this depth, at which 

 the digging was abandoned, at 25 feet below tide. 



The whole section, from the top of the highest undoubted 

 eocene stratum to where the digging ceased (without any indica- 

 tion of being near the end), is 61 feet and if the clay and gyp- 

 sum stratum below the miocene be added, which, though not cer- 

 tain, I believe to be eocene, there would be 69 feet. And if this 

 and the two other lower clay strata be deducted, there will still re- 

 main 45 feet of strata exposed, all rich in green-sand, and of it 9 

 feet very rich also in sulphate of lime or gypsum, and 11 feet mode- 

 rately rich in carbonate of lime. Such a deposit is well worth the 

 examination of geologists and chemists, and the trial of farmers. f 



It was remarkable that at this place only of all the usual strata 

 of all the then known deposits of green-sand or eocene marl in 

 Virginia, were found exposed, the shells of the ostrea compressi- 

 rostra and below tide the other before unknown and very thick 

 and heavy ostrea ; J and that at this place there has not been found 

 a single shell of either the ostrea settceformis or cardlta plam- 

 costa, the latter of which is so abundant through all other known 

 eocene deposits, and the former in the calcareous eocene else- 

 where. These facts seemed to indicate (as well as the general 

 dip to the eastward) that the strata at Evergreen are much more 

 elevated than the same at Coggins Point and that by digging 

 deeper, the lower and all the strata of the former might be found 



* One of these last (both valves) weighed 5 Ibs. Mr. M. Tuomey, to 

 whose much better information on this subject I ought- to defer, supposes 

 this very large and heavy shell to be an 0. compressirostra of unusiial age 

 and growth. If so, however, it is certainly very different in appearance 

 from that shell, as usually seen higher up in this bed, even when wider 

 than this very thick and heavy ostrea. 



[f The lowest known layer of this rich deposit has since been traced 

 three miles westward to City Point ; and from the latter place the marl has 

 been used extensively, and to much benefit. 1851.] 



J This last shell I have since learned (by specimen) is also found in 

 the green-sand marl at North Wales, near the upper termination of the 

 Pamunkey bed and near the bottom of the marl. And later personal in- 

 spection has shoyn clearly the identity of the deposits and the fossils at 

 these two points ; one being the bottom of the Pamunkey bed, and the 

 other nearly (as is presumed) to the bottom of the James river bed of 

 green-sand marl. 



