456 PROCEEDINGS OP THE GEOLOGICAL SOCIETY. [May 24, 



Dr. Fitton, in his paper " On the Strata below the Chalk " *, 

 describes pipes and furrows in calcareous beds, lined with clay 

 which also caps horizontally the limestone. In these cases the clay 

 is certainly not the result of chemical action npon the subjacent 

 beds, as it forms part of the Purbeck and Portland series. At 

 p. 276, Dr. Fitton figures and describes a pipe in the Portland 

 Beds at Great Hazeley, in which " dark brown clay like fuller's 

 earth " overlies the calcareous beds and passes round the pipes. 

 Speaking about Oxfordshire, Berkshire, (fee. Dr. Fitton says (p. 279), 

 '' in a great number of the quarries in this part of the country, the 

 ferruginous sands at the upper part (Lower Greensand) are sepa- 

 rated from the rubbly stone beneath (Purbeck) by a dark tough 

 clay, 4 to 9 inches thick, which follows the irregularities of the 

 mass below, and coats the bottom of cavities like the ' gulls ' of 

 Hazeley " f. 



Mr. Conybeare describes similar appearances at the junction of 

 the Kimeridge Clay and Coral Rag J. 



In most of the cases mentioned by Dr. Fitton, the clay is stated 

 either to consist of, or to contain, "fuller's earth." It is worthy of 

 note that the Sandgate Beds, which universally, as far as we know, 

 line the Maidstone pipes, are of this nature. 



Mr. Prestwich, in his paper on " Pipes " already alluded to, 

 notices the effect of a bed of clay in the cases of the pipes in the 

 Chalk. He says (p. 79), " As the gravel is generally without any 

 such partially impermeable seam at its base as occurs in the Tertiary 

 sands, the underlying chalk surface seems to have been liable to be 

 attacked by the acidulated waters in a greater number of places, and 

 to present a larger proportion of pipes and indentations than when 

 overlain by the sands," with the clayey band at their base. The 

 eifect of the Sandgate Beds is no doubt similar : they hold up the 

 water which sinks through the porous bed above, and thus protect the 

 limestone beds below in most places. At those points, however, where 

 the clay is in any way permeable, much water passes down, and che- 

 mical action goes on rapidly. The clay therefore serves to con- 

 centrate at particular points or along particular lines that action 

 which, were no clay present, would be distributed pretty equally 

 over the whole area. Here we may add that, in the case of the harder 

 limestones, Mr. Prestwich suggests (p. 80) that the pipes are likely 

 to have resulted from the water- wear " being directed into given 

 channels by pre-existing cracks or fissures ;" he adds, " some gravel- 

 pipes at Maidstone afford excellent illustrations of such results." 

 The marked parallelism of the long pipes at Maidstone is an argu- 

 ment in favour of their having been originally started along joints 

 or fissures. 



Mammalian Remains at Bougliton. — In the year 1827 Mr. Brad- 

 dick found some Mammalian bones in what appear to have been small 



* Trans. Geol. Soc. 2nd series, vol. iv. 1836, p. 275 et seq. 

 t These pipes are also noticed by Mr. Hull, ' Mem. &eol. Survey,' Sheet 13, 

 p. 11 (1861). 



J ' Outlines of the Geology of England and Wales,' p. 189 (foot-note), 1822. 



