ALLUA^UM AND PEAT. 229 



A deposit of tufa and tufaceous marl lying on the top of the 

 cliif at Widdick Chine has attracted a good deal of attention. 

 This tufa is a deposit from the springs given out by the Headon 

 Limestone immediately above. There is nothing to point to its 

 being of any great antiquity, for the stoppage of the springs is 

 merely due to the recession of the cliff, by which they have been 

 tapped at another point. The section is now almost entirely 

 overgrown. These deposits were first noticed and described 

 by the late Mr. Joshua Trimmer (Quart. Journ, Geol. Soc, 

 vol. X. p. 53 (1854)), and were subsequently referred to in 

 greater detail by Professor Forbes ('^ Memoir on the Tertiary 

 Fluvio-marine Formation," p. 8), and in notes by Mr Bristow 

 appended to his Memoir. When the first edition of this Memoir 

 was published this deposit could be seen to occupy the upper 

 part of the cliff in Totland Bay for a distance of nearly 

 350 yards, at about 60 feet above the sea. On the top 

 (Fig, 81) lay an unequal thickness of brown loam, containing 



Fig. 81. 

 Tufaceous deposit of Totland Bay. 





a. Ferruginous brown sandy loam. 



b. Brown clay and perished shells. 



c. Fine tufa. 



d. Coarser tufa. 



e. Potamomya sands of the Upper Headon Beds. 



a few scattered angular flints, beneath which was a layer of 

 brown clay and decayed shells, resting on four or five feet of 

 calcareous tufa (with a few black lines derived from decomposed 

 vegetable matter), sometimes equalling fluvio-marine limnaean 

 limestone in hardness. This tufa was finest in the upper part, and 

 became gradually coarser towards the bottom, where it was full 

 of round calcareous concretions of various sizes, and of what seemed 

 to be the twigs and stems of plants, which having fallen into 

 water highly charged with carbonate of lime became incrusted 

 with it. The concentric concretions were largest at the base of 



