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



blocks of the same stone lie in the line of the front of some cottages, and are 

 built into the walls. In Dr. Kidd's Geological Essay, p. 177, a similar col- 

 lection of siliceous boulders is described as scattered over a dry valley, high 

 up on the chalk downs of Berkshire, near Ashdown Park, on the south of 

 Swindon, so thickly as to render the road inconvenient, even to a foot tra- 

 veller. Although these blocks have been entirely separated from the matrix 

 in which they were formed, they are very slightly rolled, and have been 

 drifted but to a small distance from their native place. 



We think it right to refer to the action of water, probably in more than 

 one period of the tertiary formations, certain deposits of angular gravel which 

 occur on the summits of many hills within our district. A remarkable ex- 

 ample of this kind, composed of an admixture of unrolled chalk flints with 

 yellow clay and sand, is seen in the upper margin of the cliffs at White Nore, 

 where it forms a continuous bed, varying in thickness from two to twenty 

 feet, level at its upper surface, but extremely irregular below, and filling up 

 deep holes and furrows {puits naturelles), which pervade the entire surface 

 of the subjacent chalk. 



These deposits seem due to the effect of water dissolving the chalky matrix 

 of the flints, but not sufficiently agitated to roll them into pebbles, nor to 

 move them from the spot on which the dissolution of the chalk had taken 

 place. The most instructive example we know of the effects of this dissolving 

 operation is at Dunscombe Hill, on the east of Sidmouth, where, on the 

 summit of a ridge of chalk, of which the surface is furrowed with pits and 

 hollows that are evidently due to the action of water, we find an unstratified 

 mass of chalk flints, which have not undergone the slightest rolling, piled on 

 each other, and intermixed with loose sand and clay ; the outer portions of 

 this mass, from which the rain has washed away the sand and clay, lie loose 

 and hollow, like stones in an artificial barrow, or in a wall constructed without 

 mortar. It is scarcely possible to explain the actual state and position of 

 these flints but by supposing that the chalk in which they were formed has 

 been gradually dissolved in a quiet sea. To the same operation of quiet 

 solution we must also refer analogous deposits of angular chalk flints and 

 yellow clay which fill the irregular and deep troughs and hollows that fringe 

 the upper margin of the chalk in the cliffs from Lyme to Axmouth, in a 

 manner similar to that we have described at White Nore. 



Cavities and projections of this kind appear to be universal on the surface 

 of the chalk wherever it is covered up with any kind of tertiary strata, and 

 has been protected by them from the levelling effects of atmospheric agents; 

 in all these cases the actual surface of the land affords no indications of the 



