62 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



Additional Observations on the Occurrence o/" Pipes and Furrows 



in Calcareous and Non-calcareous Strata*. 



By J. Trimmer, Esq., F.G.S. 



[Read Juue 21, 1854t.] 



The following observations, which are necessary for the full under- 

 standing of the views I have taken on the origin of sand-pipes and 

 furrows in and on the surface of strata, are offered in support of some 

 positions I have taken in my former papers on the subject, and which, 

 from their not having been fully elucidated, require some explanatory 

 remarks in their defence. 



1. It was not my intention to assert in a former paper J "On Pipes 

 aud Sand-galls in the Chalk of Kent" that the Thanet Sands are cal- 

 careous, as Mr. Prestwich has been very naturally led to infer in his 

 memoir read before the Society, Jan. 18, 1854, from the expression, 

 " The sand with which the pipes are filled contains much calcareous 

 matter." This calcareous matter was chalk, redeposited near the 

 lining of the pipe from water charged vdth bicarbonate of lime. 

 Having sent a specimen of it with the paper, I did not think it ne- 

 cessary to enter into fuller explanations. 



2. I have stated § that I saw miniature pipes actually forming by 

 the mechanical action of water on blocks of siliceous sandstone, on 

 the sea-shore near Reculver. Mr. Prestwich replies, that this sand- 

 stone contains some carbonate of lime. It appears by Mr. Prest- 

 wich' s papers 11 on the Eocene Tertiaries, that the cliffs at Reculver 

 yield two sandstones, the one belonging to the Thanet Sands, the 

 other to the London Clay series, — the former calcareous, the latter 

 but sHghtly so. On blocks of one of these, I saw the flux and reflux of 

 the waves drilling small cavities, analogous to the pipes in the chalk. 

 Mechanical action may take place on calcareous as well as non- 

 calcareous rocks ; and it is no proof that the mechanical action which 

 I saw in actual operation was chemical action, even if the stone on 

 which it was taking place effervesces in an acid. 



3. With respect to the blocks scattered about the neighbourhood 

 of Faversham, on which there are furrows and pipes similar to those 

 of the chalk, though of smaller dimensions, and which I regard as 

 the completion of the process which I saw in operation on the sea- 

 shore, Mr. Prestwich admits the blocks to be siliceous, but considers 

 the furrows and cavities to be the result of concretionary structure. 

 This is a point which I am content to leave to the verdict of geologists. 

 Even, however, if in this case the appearances on these blocks are of 

 concretionary origin, it is an undoubted fact that pipes are seen oc- 

 casionally on siliceous rocks, those of the Greensand for instance, and 

 even in sand and gravel. 



* See Quart. Journ. Geol. Soc. No. 39. p. 231. 



t For the other Communications read at this Evening Meeting, see vol. x. 

 p. 454. 



X Quart. Journ. Geol. Soc. vol. i. p. 300, &c. 



§ Proc. Geol. Soc. vol. iv. p. 7. 



II Quart. Journ. Geol. Soc. vol. viii. p. 243, &c. and vol. x. p. 125. 



