238 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jan. 18, 



pure geology, having reference to the agencies concerned in their 

 formation, but having reference also to practical questions in agricul- 

 ture connected with drainage, evaporation, the patches of burning 

 soil technically called " scalds," and to the practice of deep or shal- 

 low ploughing, and subsoiling. Fig. 5 has special reference to the 

 latter point. 



To the above sections I now add from my note-book a sketch (fig. 7) 

 of furrows and pipes in another form of Boulder-clay, overlying the 

 fossiliferous portion of the Crag near Raveningham Hall, in South 

 Norfolk. 



Another deposit, whose surface, when deimded, is seen to be 

 furrowed and pierced with small pipes, filled with warp-drift, 

 consists of those beds of reconstructed chalk, pure enough to be 

 burned for lime, which are found in the midst of the sand of the 

 Upper Erratics. I described them in the ' Proceedings of the Geolo- 

 gical Society,' vol. iii. p. 185, and in the 'Journal of the Royal 

 Agricultural Society,' vol. vii. p. 463, but gave no sections. I am 

 doubtful whether the bed " r " in the section near Burnham Market*, 

 fig. 14, in which, among many small pipes, there is one 20 feet 

 deep, belongs to this portion of the erratic period, or to that of the 

 boulder-clay, which in that part of Norfolk assumes its most chalky 

 form. 



Fig. 8 represents pipes and furrows on the surface of the fresh- 

 water deposit at Gaytonthorpe -j-, which rests upon one of these 

 chalky varieties of boulder-clay, and which I therefore refer to an 

 elephantine period |, subsequent to the desiccation of the Erratic 

 Tertiaries. 



Fig. 9 is a section taken nearer the head of the same valley, and 

 represents pipes and furrows on similar deposits, in which no or- 

 ganic remains have been found. 



The furrows in the Green-sand of Kent filled with loam, and 

 containing land-shells and mammalian bones, as described by Sir R. 

 Murchison §, I refer to this second elephantine period. 



Conclusion. — On the whole, then, I conclude that pipes and fur- 

 rows have been formed by the mechanical action of water, before the 

 matter with which they are filled was deposited ; and the nearest 

 existing analogies I can find to them are the effects of breakers on 

 the shore, and of the action of torrential rivers. 



Their general distribution may be explained by the continued 

 advance or retreat of the coast-line, during the repeated risings and 

 fallings of the land throughout the tertiary era. The difference in 

 magnitude between these ancient excavations and those now being 

 formed by the sea, may be ascribed to the greater magnitude of 

 waves, occasioned by the movements to which the land, quiescent 

 now, was subject then. The prevalence of cyhndrical cavities in the 



* Quart. Journ. Geol. Soc. vol. i. p. 315. 



t Quart. Journ. Geol. Soc. vol. vii. p. 26. 



X See Table, Quart, Jouru. Geol. Soc. vol. ix. p. 295. 



§ Quart. Journ. Geol. Soc. vol. vii. p. 382, &c. 



