13 



With reference to the first of these, the Thanet Beds, the author 

 remarked, the chalk, oa which this bed rests, is considerably eroded, and 

 in this district it is chieHy the newest, or Margate chalk with few flints, 

 that is met with immediately under the Thanet Bed. In the Pegwell 

 Bay section a considerable mass of tabular flints marks the junction, but 

 elsewhere this is absent. More westward the chalk beneath the 

 Thanet Beds contains more flints, and is, presumably, a lower part of the 

 series. In most cases the Thanet Beds repose on an eroded surface of 

 chalk, but the irregularity is confined to minor excavations ; on the 

 larger scale it rests conformably to the chalk strata. It is, nevertheless, 

 apparent that the chalk had been subjected to some denudation previous 

 to the deposition of the Thanet Beds. The latter have been deposited in 

 a depression in a chalk basin formed at the commencement of the 

 Eocene period. Comparing the thickness of the Margate chalk, in the 

 Isle of Thanet, underlying the Thanet Sand, with the thickness of the 

 same division of this formation nearer Canterbury, it would seem that 

 the lesser thickness, in the latter case, must be due to denudation. 



It was remarked that the junction of the Thanet Bed with the chalk 

 is everywhere marked by the occurrence of gi'een coated flints, and these 

 follow the eroded surlace down into the pipes and cavities of the chalk. 

 These pipes in the chalk are apparently caused by the rain water finding 

 its way down through the tertiary beds, and so dissohdng away the chalk, 

 and then the Thanet Bed sinks down into the pipe, carrying with it the 

 superincumbent green-coated flints. There are not found more flints in the 

 eroded pipes than at other junctions with the chalk ; indeed, the chalk, for 

 the most part, is so destitute of flints, that it would require a large amount 

 of denudation by this means to account for the number of the green-coated 

 flints. Another fact relating to this eroded siu-face of the chalk, was 

 alluded to, viz., that in some cases the erosive action had been continued 

 so as to bring down the drift fi'om above to fill up the pipes, and in 

 large pipes this was particularly the case. A very curious instance of 

 this was noted in a Chalk Pit at the A'orth-west end of the Elham 

 Valley llailway cutting, known as Chapman's Chalk Bit, occurring at 

 the slope or ridge of the chalk skirting the Valley of the Stour. 

 In this large pipe the bottom and sides are lined with the Thanet Beds 

 and junction bed of green-coated flints, inside of which the pipe is fiUed 

 with subangular gr-avel, which forms some concentric layers of washed 

 flints ; in this case the further erosion of the chalk seems an-ested at the 

 close of the time when the drift was formed. The more recent gravel 

 and drift above passing regularly over this pipe. 



Of the green-coated flints it was remarked that there were two 

 theories to account for them ; the one advocated by Mr. Whitaker and 

 Mr. McKenny Hughes, and the other by the Author. By a curious 

 coincidence they both appeared at the same time in a letter to the 

 Geological Magazine, in Vol. iii, pp. 216-239 and Mr. Hughes' in Vol. xiii, 

 p. 18, of the Joiu-ual of the Geological Societg. As Mr. Hughes' theory 

 is the one generally accepted, his words are given in extenso : — 



