210 Mr. Webster on the Strata lying over the Chalk, 



§ 3. Lower Freshwater Formation. 



This formation is to be seen most distinctly in the section of 

 the hill called Headen, which forms the northern boundary of 

 Alum bay, in the Isle of Wight. It appears there in a series of 

 beds of sandy calcareous and argillaceous marls ; sometimes with 

 more or less of a brownish coaly matter. Some of them appear to 

 consist almost wholly of the fragments of freshwater shells, many 

 of which are however sufficiently entire to ascertain their species. 

 These are the lymneus, planorbis and cyclostoma, and perhaps the 

 helix ; with a bivalve resembling the freshwater mytilus. 



These beds lie immediately upon the black clay that covers the 

 white sand, described in the account of Alum bay. They are 

 extremely irregular, and are not to be traced distinctly from each 

 other for more than about a few hundred yards, the remaining 

 part being so hid by the mouldering slope, that the formation can 

 only be observed in mass. It may be seen however extending 

 round the north side of Headen into Totland bay, where it forms 

 the upper part of the cliff: and at the point called Warden-ledge, 

 it is found in a more uniform and indurated state. Here, when 

 the clay upon which it rests gives way from the rain and frost, 

 large masses of it fall down, which are employed for the purposes 

 of building, though the stone is not of a good quality. Pursuing 

 it farther into Colwell bay, it dips to the north, and is soon lost ; 

 nor is it to be seen any more on that side of Yarmouth. At the 

 bottom of these beds, and between them and the black clay, there 

 is frequently a layer of two inches or more in thickness of a dark 

 brown coaly matter, much like what is usually found at the bottom 

 of peat bogs, and it appears to be a similar substance that tinges 

 many of the beds. 



