the Coralline Crag at Sudbourn and Gedgrave near Orford. 321 



and that tue hypothesis proposed by Su- Charles Lyell is the 

 true one for the funnel-shaped depressions, while there is also 

 no doubt that the surface of the chalk has in some places been 

 eroded as described by Mr. Trimmer. 



The cavities immediately below the superficial soil on the 

 eastern side of England might, I think, be classed under three 

 distinct heads, as they are not only the presumed productions 

 of different agents, but also the result of actions very dissimilar 

 in their operations. The first are the well-known " puits natu- 

 rels," which from their peculiar forms may for mere distinction 

 be called funnel pipes ; the second may be termed ffullj/ pipes ; 

 these, however, are not, strictly speaking, pipes at all, as they 

 all terminate in a closed point ; and the thn-d more correctly 

 chimney pipes. ' 



The first or funnel pipes are more or less of an angular form, 

 irregular in outline, and where it is possible to ascertain their 

 full extent, they invariably terminate in a point. These are not 

 only common on the surface of the chalk, but are very nume- 

 rous, though generally small in size, upon the coralline crag; 

 and in the parishes of Sudbourn and Gedgrave, wherever a 

 section of this formation is visible, the whole surface is more 

 or less excavated in this manner, and none that I could see 

 exceeded in depth 3 or 4 feet, while 12 or 18 inches was the 

 diameter of the upper part. The larger and deeper pipes of the 

 chalk may be due to the erosive action having been prolonged 

 through a much greater period; and in examining the contents 

 of two or three of these excavations, which were filled with the 

 superincumbent gravel, not a single fragment of shell could be 

 observed, or any trace of carbonate of lime, which might have 

 been the case had they resulted simply from the action of run- 

 ning waters ; moreover, the edges of these depressions were too 

 sharp in a material so loose and incoherent as is the coralline 

 crag, and their positions too proximate for the probable action 

 of any other agent than the slow and gradual process of a che- 

 mical abstraction acting from above. 



The second class, or gully pipes, are described by Mr. Trim- 

 mer as having been formed by the action of running waters 

 draining the surface of the chalk previous to its elevation above 

 the .sea, and the angular depressions visible in that rock, and 

 now filled with gravel, are merely the transverse sections of these 

 gullies ; and he further states his having removed for a consi- 

 derable space the superincumbent material and exposed the con- 

 tinuance of these depressions. Another form of excavation may 

 also here be mentioned as being more in connexion with this 

 last mechanical mode of operation, and is spoken of by Lieut. 

 Ncwbold as occurring in southern India, wherein he describca 



Phil. Mag. S. 4. Vol. 7. No. 46. May 1854. Z 



