1854.] TRIMMER ON THE ORTON GRAVEL. 345 



examination, I should hesitate to affirm that which I believe to be 

 the case, namely that we have here an ancient marshy surface 

 beneath the warp-drift. 



The boulder-clay contains a large proportion of chalk and chalk- 

 flints, with other fragments of still more distant origin, imbedded in 

 a base of brown clay. It forms a ridge extending from north to 

 south, and therefore in a direction transverse to this part of the 

 Valley of the Nene. It is based on Oxford clay. 



The Orton gravel is spread over the Oxford clay and the oolitic 

 rock in a direction parallel to the valley, and extends to a height of 

 20 feet above the level of the Nene. 



The two gravel-pits which have yielded mammalian remains, 

 associated with terrestrial, marine, and fluviatile shells, are situated 

 near the Hall, and about 176 yards from the road from Peterborough 

 to Northampton. From that nearest to Peterborough, in a pasture- 

 field, bones have been obtained, irregularly dispersed, as I was in- 

 formed by the workmen, through the gravel. They are more abun- 

 dant in another pit, in an arable field, distant about 460 yards from 

 the former and about 200 yards from the road. 



In the former pit the gravel has been worked to the depth of 1 

 feet, without reaching the rock. 



At the depth of 7 feet, I found Cardium edule and Ostrcea edulis, 

 in the state of large fragments in a very decayed condition. 



At the pit in the arable field, the gravel is worked down to the 

 oolitic rock on which it rests ; and the total depth of the deposit, of 

 which the following is a section, varies from 12 to 14 feet. 



Section of the Mammaliferous Gravel of the Nene Valley ; from a 

 gravel-pit near Orton Hall. 



a. Warp-drift of brown loam, filling indentations in surface of 4. 



b. Gravel. 



c. Alternations of sand with gi-ey and brown clay ; — freshwater and land shells. 



d. Gravel ; — mammalian bones and marine shells, both near the bottom of the bed. 



e. Oolitic rock. 



2 B 2 



