Mr. De la Beche on the Geology of Part of France. 75 



The chalk throughout this tracts which forms a high table land,, is for the 

 most part concealed by flint gravel*, generally angular, and sometimes form- 

 ing beds exceeding one hundred feet in thickness. 



The valley of the Rille, from Pont Audemer to Brionne, affords a distinct 

 section of the chalk with its thick coating of gravel beds. At Brionne this 

 rock contains very few flints, and it is equally destitute of them at Cormeilles^ 

 on the banks of the river Calone. The strata of the whole body of chalk have 

 a gentle inclination to the E.N.E. The surface occasionally presents great 

 inequalities, assuming the form of pyramids or neediest, &c. 



Green Sand, and Iron Sand. 



Green sand appears under the chalk at Cap d'Antifer, and forms the lower 

 part of the cliffs as far as Cauville, where marl, containing green earth, may 

 be observed under it. From thence to Cap la Heve the shore is encumbered 

 by fallen masses of chalk and green sand. At Cap la Heve this thin marl bed 

 is again seen beneath the green sand. It rests upon iron sand, containing 

 mica and siliceous grains, which are sometimes as large as peas ; and this 

 again upon blue marl and marlstone. 



Between Cap d'Antifer and Cauville the green sand contains numerous 

 Alcyonia, several varieties of Echini, Ostrea crista-galli (Parkinson), Turrilites 

 costata;):. Ammonites Goodhallii, &c. At the Vaches Noires it abounds with 

 fossils, one of the most remarkable of which is, the Hallirhoa costata§ of 

 M. Lamouroux. 



At Henqueville Cliff, on the south of the Seine, the green sand is again 



* The farmers occasionally sink pits through the gravel, when not very thick, in order to ob- 

 tain the chalk. 



t In England also, at Dunscombe Hill and Quarry, on the coast of Devonshire, the cliffs exhibit 

 a few detached portions of chalk, ten or twenty feet in height, resjng upon green sand and 

 covered by unrolled flint-gravel. 



X The names of fossil shells throughout the remainder of this communication, are those given in 

 Sowerby's Mineral Conchology, 



§ Exposition M^thodique des Genres de I'Ordre des Polypiers. Paris 1821. — M. Lamou. 

 roux appears to have been led into error with regard to the rock at the Vaches Noires, in which 

 these fossils are found : their locality is in the green sand, and not the blue clay (Oxford clay) 

 beneath it. The green sand is continually falling down, and in consequence its fossils frequently 

 become imbedded in the soft clay at the base of the cliff. — Fig. 5. Plate IX. shows the interior 

 •tructure of these fossils; which are found also in the green sand of Warminster in Wiltshire. 



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