T II E 



LONDON AND EDINBURGH 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[THIRD SERIES.] 



OCTOBER 1839. 



XXXV. On the tubular Cavities Jtlled isoith Gravel and Sand 

 called " Sajid-pipeSi " in the Chalk near Norwich. By 

 Charles Lyell, Esq., F.R.S., V.P. G.S., ^c* 



THE white chalk with flints in the neighbourhood of Nor- 

 wich, is covered with a mass of variable thickness of 

 irony sand and gravel, with some intermixture of red clay, 

 the sand passing occasionally into a ferruginous sandstone. 

 The surface of the chalk when the gravel is removed is ex- 

 tremely uneven, presenting sharp ridges, deep furrows, and 

 pits, and some protuberances which are larger at the summit 

 than the base. In a word, it is impossible to conceive that 

 so soft a rock as chalk could have acquired such an outline 

 simply by ordinary denudation, or could have retained it if 

 once acquired during the accumulation of the mechanical de- 

 posit now superimposed. It is equally difficult to refer to 

 any known mode of denudation those deep and narrow hol- 

 lows, filled with sand and gravel, which are the same as those 

 called in France " puits naturels," and which will form the 

 subject of the present communication. 



Form of the Sand-pipes at Eaton. — I was indebted to Mr. 

 Ewing for first calling my attention to some fine example; 

 of these phaenomena which he had accurately observed on his 

 property at Eaton, about two miles west of Norwich, where 

 the chalk has been extensively excavated for the manufacture 

 of lime. Cylindrical hollows filled with loose materials, evi- 

 dently derived from the overlying tertiary formation, are here 

 called "Sand-pipes" by the workmen. They resemble those 

 which occur in many other districts in England, where the 

 chalk is covered by sand and gravel. 



* Communicated by the Author. 



Phil. Mag. S. 3. Vol. 15. No. 96. Oct. 1839. S 



