24 GREEN SAND FORMATION. 



§ I. GREEN SAND FORMATION. 



In conformity with the arrangement of Professor Buekland, the whole 

 of the Sussex beds below the chalk marl, are included in the present 

 formation, although they differ most essentially from each other, both in 

 their physical characters, and in the nature of their organic remains. 

 But the term for^nation is now employed by geologists in a very extended 

 sense, denoting not only a series of similar and contemporaneous strata, 

 but also an assemblage of contiguous beds, which although differing from 

 each other in dimensions, colour, constituent substance, mineralogical 

 productions, and organic remains, are yet presumed to be more nearly 

 related to each other, than to any other group of deposits. 



V. 

 § I. 1. IRON SAND, 



CONSISTING PRINCIPALLY OF FERRUGINOUS SAND AND SANDSTONE, AND CONTAINING SUBORDINATE 

 STRATA OF IRONSTONE, MARL, AND CLAY, WITH SHELLY LIMESTONE; ALTERNATING IRREGU- 

 LARLY; AND ALSO BEDS OF WOOD COAL. 



The iron sand is considered by Mr. Conybeare as the lowest of the 

 formations which intervene between the ooHtes and the chalk. The 

 sand and sandstone are entirely siliceous, and contain a great proportion 

 of brown or yellow oxide of iron ; often indeed in such quantity, that 



