322 Mr. S. V. Wood on some Tubular Cavities in 



the sui-face of the rock as eroded into cup-shaped cavities pro- 

 duced by the action of nmning waters, whose eddies or gjrations 

 have by the trituration of sandy particles worn them into a sub- 

 globular form. These poteria or cup-shaped cavities are spoken 

 of by Mr. Trimmer (p. 498) as having been observed by him on 

 the surface of the chalk at Thorpe and Rackheath in Norfolk, aa 

 also in Kent : these he considers as incipient pipes, and they are 

 presumed to be identical with those rock basins described by Lieut. 

 Newbold in the Proceedings of the Geological Society, vol. iii. 

 p. 702. Mr. Jukes also, in his account of Newfoundland, vol. ii. 

 p. 138, mentions similar excavations close to Buchan's Island in 

 the river Exploits, and particularizes two holes worn in the rock 

 of a form somewhat singular, being perfectly perpendicular to 

 the depth of 8 feet, with a diameter of about 2 feet ; he says 

 they were exactly circular, nearly full of water, and each con- 

 tained a large stone and a quantity of sand at the bottom, and 

 these were so produced by the whirling round of the stone from 

 the rapidity of the current of water rushing over them. 



The third class are what I propose to call chimney pipes, 

 and are more especially the subject of the present notice ; their 

 form, as well as the mode by which it is presumed they were 

 produced, being wholly different from the before-mentioned ex- 

 cavations, they appear to be deserving of a jjarticular designation. 



In a quarry of the coralline crag at Sudbourn near Orford, 

 close to the gate which leads to the mansion of the Marquis of 

 Hertford, are a number of these "pipes;" not less than nine 

 wei'e visible within the space of twenty yards when I visited the 

 pit, all nearly of the same size, and excavated perpendicularly or 

 nearly so, one only appearing to decline a little from that direc- 

 tion : the general dimensions of these pipes were about 18 

 or 20 inches in diameter. And in another pit in the parish 

 of Gedgrave, at the distance of about a mile due south of this, 

 may be seen also eleven more of these perforations, one of which 

 is much larger than the others, with a somewhat different form 

 (Plate V.)*. 



The coralline crag in this locality consists of a sort of low 

 table-land, bounded or rather cut off on the N.E. by the river 

 Aide, and extending to the S.W. about five miles, where it is 

 again cut out by the small river that runs up to Butley, having 

 a transverse direction of about two miles and a half with a vari- 

 able thickness ; and a depth of 50 feet is reported to have been 

 pierced through without coming to the clay. Wherever a sec- 

 tion of this is visible, it appears to have formed on the upper 

 part a complete coral bank, beneath which, as seen in the valleys 



* The Plate is from a sketch of some years date, and the pit at that part 

 has since been worked, by which a coi^siderable alteration is made. 



