ON THE FORMATION OF MURAL CLIFFS. 59 



ON THE FORMATION OF MURAL CLIFFS. 



91. There is one characteristic of mural cliffs, 

 which, so far as my observation goes, is common to 

 all, whether those cliifs occur inland or upon the 

 sea-shore. At the base of those cliffs, and along 

 the whole extent of the base, a stratum of rock 

 occurs of softer consistency than the superincumbent 

 rock. When, therefore, a series of strata, somewhat 

 inclined to the horizon, is situated upon the sea- 

 shore, with their escarpments exposed to the action 

 of the waves, and the inferior stratum is composed 

 of softer material than the superincumbent rocks, 

 the stratum of softer consistency undergoes a more 

 rapid abrasion than the rocks above; and because 

 of this, those rocks are left unsupported, and from 

 time to time give way, and thus a mural cliff, with 

 a perpendicular face, is formed. 



92. On those parts of the coast where the sea has 

 made rapid encroachments upon the dry land, I 

 have observed that this occurs more particularly 

 where a cliff rests upon a thin stratum of rock, of 

 which the consistence is of softer material than the 

 rock of which the cliff is composed. The sea ex- 



