22 Prof. BucKLAND and Mr. De la Beche on the 



On the opposite side of the Channel the Kimmeridge clay occupies the 

 cliffs of Havre and Honfleur, where it lies next beneath the greensand^ and it 

 has been further identified by M. Elie de Beaumont^ and by M. de Dufrenoy 

 in the South of France. This formation exhibits its best sections and highest 

 elevation near the east extremity of our district in the cliffs of Ringstead Bay 

 and Osmington^ where it attains a thickness of about 300 feet. 



From Osmington Cliff it continues westward^ without interruption^ through 

 Preston and Upway Street to Abbotsbury, forming the narrow north belt of 

 clay which we have named from the village of Upway Street. Great part of 

 this belt is marked by a valley parallel and subjacent to the ridge of Portland 

 stone above described^ and dividing it from the ridge of Oxford oolite which 

 forms its southern frontier : this belt of clay terminates suddenly about one 

 mile west of Abbotsbury. In the Vale of Bredy, the covered state of the 

 country renders it almost impossible to distinguish the Kimmeridge clay 

 among the different clay beds that occupy a large part of its surface ; but we 

 have identified it at Litton Cheney^ immediately on the south of that village, 

 containing the Gri/phcEa Virgula. 



The southern belt of Kimmeridge clay near Weymouth, occupies a very 

 small portion of the surface, constituting a triangular area, the base of which 

 extends about a mile from Sandsfoot Castle westward, to the Chesil Bank, 

 whilst its apex is at Portland Ferry : but although so small a portion of this 

 belt of clay is here visible on the surface, we have evidence of its submarine 

 continuation from hence to Portland Island, in the clay bottom of the excel- 

 lent anchorage of Portland Road, beyond which also it appears above the 

 level of the sea in the base of the escarpment at the north extremity of the 

 Isle of Portland, and along its west shore also immediately south of the village 

 of Chesilton. Hence it is clear that the Kimmeridge clay forms the fundamental 

 stratum of the whole island, separated, as we have shown, from the Portland 

 stone by the Portland sand and sandstone last described. The rapid dip 

 of all these strata towards the south, causes the Kimmeridge formations to 

 sink below the level of the sea in the southern portion of the island ; whilst 

 that part of its western coast, whose base is composed of these perishable 

 sands and clays, is defended from the tremendous south-western waves by a 

 natural breakwater of enormous masses of Portland stone that have fallen 

 from the summit, and form a barrier against any further encroachments*. 



At a point near Portland Ferry, extending over many yards of the shore. 

 Dr. Buckland remembers to have seen, several years ago, a portion of Kim- 



* See Plate III. fig. 3. 



