Mr, Warburton on the Bagshot Sand: 51; 



circumstance excepting the absence of angular masses of flint. At a lower 

 level are found beds of foliated green clay^ alternating with beds of green 

 sand : extensive beds of this clay are found to the north of Chobham Park^ 

 on the road from Chertsey to Bagshot^ where they are worked for the making 

 of bricks and coarse pottery. It is in the beds below this green clay that we 

 find the most unequivocal proof of the sand of Bagshot Heath belonging to a 

 regular stratum. These lowest beds are found on descending the acchvity to 

 the south of Chobham Park. They consist of alternations of white, sulphur- 

 yellovv, and pinkish foliated marls, containing abundant grains of green sand, 

 regularly stratified, and inclosing fossil shells, such as have not hitherto been 

 found in England in any other bed above the chalk with which I am ac- 

 quainted. The entire thickness of these lower beds may be about forty feet. 

 The white foliated marl bears a strong resemblance to that of Menil Montant, 

 in which the Menilite is found, near to Paris. 



The shelly matter of the fossil shells which these beds contain has altogether 

 perished, so that it is impossible to identify the species, though the genera may 

 be determined. The most abundant of the shells is the cast of a crassatella, 

 agreeing I believe with a crassatella found in the Paris Basin at Meudon in 

 the calcaire grassier a matiere verte, and deposited in the Society's collection. 

 The only other shells which I have found are a pecten, and what appears to 

 have been a trochus. 



At the base of the hill in which these beds are found, a blue clay, which I 

 suppose to be that of London, makes its appearance. 



Similar beds of foliated marl are found on the continuation of the Bagshot 

 sand at Addlestone near to Chertsey, but no shells have been there observed. 

 The foliated marl is there covered by a clay which strongly resembles in tex- 

 ture, though not in position, some of the varieties of plastic clay. 



At the foot of St. Anne's Hill the beds which lie nearest to the London clay 

 are different from the preceding. They consist of masses of rolled chalk-flints, 

 closely resembling those of the pebble-bed in the plastic clay, intermixed w ith 

 green sand, green foliated marl, and stony concretions of that sandstone which 

 is so generally dispersed in masses over the surface of Bagshot Heath. 



I do not believe that the Hertfordshire puddingstone has been derived 

 from the stony concretions of this bed, but rather from those of the plastic 

 clay; the cement of the puddingstone being composed of much purer siliceous 

 matter, and not being so ochreous as that of the grit of Bagshot Heath. The 

 Hertfordshire puddingstone and the greyweathers of Marlborough downs and 

 Abbotsbury contain angular chalk-flints ; and I have observed only rounded 

 pebbles in the grit in question. 



