262 SUBTERRANEAN EROSION, AND SOME OF ITS EFFECTS. 
in the low-lying drift-covered areas, underground water exists 
under great hydraulic pressure. If such water makes its way to 
the sea, it could escape far below low water. I am strongly of 
opinion that quicksands on our shores are caused mainly by the 
subterranean drainage from the land; they are in fact the points 
of escape where the underground waste oozes out. 
It must not be supposed that because I have chosen to 
illustrate the subject of subterranean erosion from a local stand- 
point, that its effects are more or less local. It is far otherwise, 
as the disaster at Sandgate, Kent, only too plainly portrays. 
In the Quarterly Journal of the Geological Soctety, vol. xlviii., 
p- 103, I defined subterranean erosion as follows :—‘‘That wher- 
ever water percolates through such unconsolidated beds as 
clays, sands, and gravels, along an inclined plane, it is constantly 
carrying the lighter materials of such strata towards the nearest 
point of escape. The nearer the approach to the point of escape, the 
greater becomes the power of subterranean erosion. This action 
causes lateral subsidence. 
All other things being equal—if subterranean erosion be true 
at all—it will prove as true in the past as in the present, and as 
wide in its operations as the law of gravitation. I maintain— 
inter alia—this “‘ principle of geology” may be responsible for 
such widely separated physical phenomena as the submerged 
Peat and Forest-beds of the Estuary of the Thames; the Dismal 
Swamps of America; the contorted Drifts of Norfolk; or the 
thick coals of South Staffordshire.” 
REFERENCES. 
1. LyELt, C. Principles of Geology, ed. 2, vol. i., p. 310, 1832; vol. ii., 
Pp. 275, 1833. 
2. CUNNINGHAM, J., on ‘‘The Submarine Forest, Leasowe.” Report of 
the British Association for 1854, Sections, p. 81. 
3. Woopwarp, H. B. ‘The Scenery of Norfolk.” Trans. Norfolk Nat. 
Soc., vol. iii, 1883, p. 439; and Geol. England and Wales, ed. 2, 
1887, pp. 596-597, S01. 
4. GRIESBACH, C. L. “Geology of the Central Himalaya.” Mem. Geol. 
Surv. India, vol. xxiii., p. 36, 1891. 
5. SHONE, W. ‘The Subterranean Erosion of the Glacial Drift ; a proba- 
ble cause of submerged Peat and Forest-beds.” Quart. Journ. 
Geol. Soc., vol. xlviii, p. 96, 1892. 
6. Morton, G. H. Letterinreply to Paper by W. SHONE. Geol. Mag. (3), 
vol. ix , p. 430, 1892. 
7. SHONE, W. Letter in reply toG.H. Morton. Geol. Mag. (3), vol. x., 
pp- 142-3. 
8. WoopDwArpD, H. B. ‘The Underground Waste of the Land.” Natural 
Science, vOl. ii., p. 124. 
Lesour, G. A. “On certain Surface-Features of the Glacial Deposits 
of the Tyne Valley.” Zhe Nat. His. Trans. of Northumberland, 
Durham, and Newcastle-on-Tyne, vol. xi., part 2. 
10. SHONE, W. ‘‘ The Cause of Crateriforn Sand Dunes and Cwms,” 
Geol, Mag. for July, 1893, p. 323. 
Notr.—I have to thank the Council of the Geological Society for allowing 
me to take ‘‘clichés”’ of the figures and sections which are reproduced in 
this Paper. 
