ON SUB-WEALDEN EXPLORATION. 349 



to the superior solvent power for carbonate of lime of the rain-water charged 

 with carbonic acid. 



The Kimmeridge Clay probably began at about 274 or 275 feet from the 

 surface. If it extends to 1769 feet, we have here a thickness of 1495 feet 

 in one continuous section, all the beds l5iug flat. The greatest thickness as- 

 sumed by Mr. Blake for the Kimmeridge Clay of England, where exposed 

 at the surface, is 1050 feet ; this thickness, however, is not present in any 

 one district. 



The Be/port of the Committee appointed for the purpose of considering the use 

 of Steel for structural purposes will be printed in the next volume. 



