MINOR EROSION FEATURES 



857 



the erosion monuments of Monument Park, Colorado (p. 53) ; the 

 facetted pebbles (p. 54) ; erosion forms produced by solution (pp. 

 174-176), by waves (pp. 221-226), by rivers (pp. 246-257), and by 

 ice (pp. 263-265). A striking example of eolian erosion is further 

 shown in Fig. 225, where alternating hard and soft limestone strata 



Fig. 226. Solution fissures in chalk, forming organ-pipe structure. The hol- 

 lo\vs are filled with sand and clay from above. (After Lyell.) 



inclined at a considerable angle were carved into fantastic forms by 

 wind. Another example, illustrating the effect of solution on lime- 

 stone, is given in Fig. 226, which shows the solution fissures in chalk 

 and other limestone regions where cylindrical depressions often 

 occur in great numbers, and close together, forming geological 

 "organ pipes" (GeologiscJie Orgcln) (Fig. 136, p. 698). Broad 

 kettle-like hollows or dolinas are also produced by solutions on 

 joint-cracks. These may be up to t km. in diameter and 30 meters 

 in depth. 



BIBLIOGRAPHY XXI. 



1. CROSBY, WILLIAM O, 1899. Archaean Cambrian Contact near 



Manitou, Colorado. Geological Society of America Bulletin, Vol. X, 

 pp. 141-164. 



2. DAVIS, WILLIAM MORRIS. 1896. Plains of Marine and Subaerial 



Denudation. Geological Society of America Bulletin, Vol. VII, pp. 



3- 



378-398. 

 DAVIS, W. M. 



pp. 207-239. 

 DAVIS, W. M. 



The Peneplain. American Geologist, Vol. XXIII, 



Geographical Journal 



1899. The Geographic Cycle. 



(London), Vol. XIV, pp. 481-584. 

 DAVIS, W. M. 1899. Physical Geography. Ginn & Co. 

 DAVIS, W. M. 1899. The Drainage of Cuestas. London Geologists' 



Association Proceedings, Vol. XVI, pp. 75-93, 16 figures. 

 DAVIS, W. M. 1900. The Physical Geography of the Lands. Popular 



Science Monthly, Vol. LVII, pp. 157-170. 



