476 GREEN-SAND OR GYPSEOUS MARL. 



the very winding course of the Pamunkey serves to make the ex- 

 posure of the bed of marl show an average width of three or more 

 miles. Throughout this area, it is found in great abundance at 

 numerous points though of great variety of appearance and of 

 value at different elevations, and in very different degrees of access, 

 or ease of working. 



This marl everywhere has its calcareous portion (which is usually 

 small in comparison to good miocene marls) intermixed with a 

 large proportion of green-sand. The calcareous earth varies from 

 10 to 40 per cent, at different diggings, or different layers at the 

 same locality ; and the green-sand perhaps from 10 to 30 per cent. 

 as estimated by the eye. In some places, the one ingredient pre- 

 dominates in quantity, and elsewhere the other. No one specimen 

 has been found rich in both of these ingredients. 



There are various and very different kinds of earth, if considered 

 in reference to their chemical constitution and qualities, and values 

 as manure, which together make up this extensive area and great 

 depth of the eocene formation ; and all of which varieties, however 

 different, have in common been deemed and termed marl by the 

 people of the neighbourhood. That all these various earths belong 

 to the same eocene formation is evident from the fossil remains, or 

 from other as certain proofs where there are no such remains visi- 

 ble. The principal and most notable of these different earths will 

 be here described. 



The most extensive exposure of calcareous marl, which I will 

 designate as L, (and embraces beds 4 and 5 in the profile view, 

 which will be hereafter given), is along the river for five or six miles 

 in a straight course, above and below Newcastle ferry ; and a very 

 much longer course, if following the crooked course of the Pamuii- 

 key. This marl is more than 24 fo^t thick at Clifton, the farm of 

 Mr. J. W. Tomlin, next below Newcastle ferry. From that locality, 

 it becomes thinner in the extensions both up and down the river. 

 At two miles above the thickest part, it gradually thins out to 

 nothing, in Marlbourne farm (my own property) ; and before reach- 

 ing the nearest outline of Marlbourne, this marl (L) is barely 2 feet 

 thick, and not worth for use the cost of removing the overlying 

 drift or other earth. This marl and all the other accompanying 

 beds, are inclined; the "dip being towards the east or south-east. 

 The ancient flood proceeding from the north-west had washed away 

 the highest raised western parts of all these beds, and reduced them 

 to their now nearly horizontal surface; and this ancient " denu- 

 ding" action is the cause of this marl, and the other beds, succes- 

 sively thinning out at the surface as proceeding up the river. 



This most extensively exposed body of marl is of four principal 

 kinds, without noticing some less important differences. The lower 

 6 or 7 feet of its thickness (x) and which includes all of 4 in the 



