CHAP. XII. MUNDESLEY FRESH-WATER FORMATION. 223 



and those afterwards thrown down above, may he perfectly 

 horizontal" (see above). 



In most cases where the principal contortions of the layers 

 of gravel and sand have a decided correspondence with deep 

 indentations in the nnderlj-ing till, the hypothesis of the 

 melting of large lumps and masses of ice once mixed up with 

 the till affords the most natural explanation of the phe- 

 nomena. The quantity of ice now seen in the cliffs near 

 Behring's Straits, in which the remains of fossil elephants 

 are common, and the huge fragments of solid" ice which 

 Meyendorf discovered in Siberia, after piercing through a 

 considerable thickness of incumbent soil, free from ice, is in 

 favor of such an hypothesis, the partial failure of support 

 necessarily giving rise to foldings in the overlying and previ- 

 ously horizontal layers, as in the case of creeps in coal-mines.* 



In the diagi'am of the cliffs at p. 213, the bent and con- 

 torted beds No. 5, last alluded to, are represented as covered 

 by undisturbed beds of gravel and sand, No. 6. These are 

 usually destitute of organic remains; but at some points ma- 

 rine shells of recent species are said to have been found in 

 them. They afford evidence at many jDoints of repeated 

 denudation and redeposition, and may be the monuments of 

 a long series of ages. 



Mundesley Post-glacial Fresh-water Formation. 



In the range of cliffs above described at Mundesley, about 

 two miles southeast of Cromer, a fine example is seen of a 

 fresh-water formation, newer than all those already men- 

 tioned, a deposit which has filled up a depression hollowed 

 out of all the older beds 3, 4, and 5, of the section, p. 213. 



When I examined this line of coast in 1839, the section 

 alluded to was not so clearly laid open to view as it has 



* See Manual of Geology, by the author, p. 51. 



