52 



could have made them. Sea work alone would make 

 but little impression on the marl, and the atmos- 

 pheric agents, unless a river flowed all along at the 

 base of the cliff, would change them into a slope ; but 

 when both work hand in hand, meteoric abrasion 

 prepares the marl to be easily carried away by the 

 sea. If such cliffs are only examined during wet 

 weather the connection between the cracks and the 

 denudation is very obscure, as the rain and moisture 

 obliterates the cracks. Such places should first be 

 examined during fine dry weather, when the different 

 systems of cracks can be plainly seen and studied ; 

 and if subsequently the same place is explored in 

 rain the mode of work of the atmospheric agents is 

 apparent. 



Very similar slips to those just described, the 

 result of a similar cause, take place in railway and 

 other artificial cuttings through marl, clay, and the 

 like. These, from what we learn in the cliffs, might, 

 in a great measure, be prevented by making artificial 

 joint lines (cuts) in them, perpendicular to the line 

 cf railway, which would act as drains to let off all 

 the water from the transverse joints, and thus 

 remove the cause of danger. 



In some climates, hardened gravel and sand, sandy 

 clay, or any other clayey drift, may form perpendicular 

 cliffs to a sea margin ; the sea action working away 

 the lower portion as fast as meteoric abrasion denudes 



